Laptop Audio Hardware

Although the first sound cards for desktop computers, the AdLib and Creative Labs Game Blaster , were introduced in the late 1980s, the first laptop computers with onboard audio were not introduced until September 1993, when IBM's ThinkPad 750 series first hit the market. Before the ThinkPad 750 series was introduced, a few laptops in the early 1990s featured PC Card-based sound cards, but these were expensive and were not popular.

Note

CardBus-based audio cards are still available, but they are used for professional sound digitizing and editing, and are therefore beyond the scope of this book.

The ThinkPad 750 series and some other early IBM ThinkPad computers used IBM's own Mwave audio chip, but by 1995 IBM ThinkPads used audio chips from Crystal and ESS, as did Toshiba and other major laptop brands that included integrated audio.

Although from the beginning laptop sound chips emulated the de facto industry-standard SoundBlaster Pro and SoundBlaster 16 cards made by Creative Labs, Creative Labs did not introduce its own sound chips for laptop computers until September 1999, when it released its EV1958 and EV1938 chips. Ironically, Creative Labs' laptop audio chips have been less popular than other brands, but Creative Labs has created two external USB-based devices that provide high-quality audio for both laptops and desktops: Sound Blaster MP3+ and Sound Blaster Extigy. These products are discussed later in this chapter.

Today's laptops continue to use audio chips from various vendors and offer better audio output and sound quality than ever before.

Audio Connectors

Laptops typically feature at least two 1/8'' minijack connectors similar to the ones shown in Figure 11.17:

• Stereo line-out or audio-out connector (lime green) The line-out connector is used to send sound signals from the laptop's audio chip to a device outside the computer. You can hook up the cables from the line-out connector to stereo speakers , a headphone set, or your stereo system.

• Microphone-in or mono-in connector (pink) The mono-in connector is used to connect a microphone for recording your voice or other sounds to disk. This microphone jack usually records in mononot in stereoand is therefore not suitable for high-quality music recordings. Many audio chips use Automatic Gain Control (AGC) to improve recordings. This feature adjusts the recording levels on-the-fly . A 600 ohm10,000 ohm dynamic or condenser microphone works best with this jack. Some laptops use the line-in connector instead of a separate microphone jack.

Figure 11.17. The microphone jack (left) and headset/speaker jack (right) on a typical laptop computer. Note the symbols used to indicate each jack's purpose.

Some laptops also have additional jacks :

• Stereo line-in or audio-in connector (light blue) With the line-in connector, you can record or mix sound signals from an external source, such as a stereo system or VCR, to the computer's hard disk.

• S/PDIF optical digital out (black) Connects the laptop to a digital amplifier such as you might find in a home-theater system. A few systems include this jack on the laptop itself, but it is more often built into a companion docking station or port replicator.

Note

When you plug a microphone into a laptop, the onboard microphone (usually located on the LCD panel or at the top of the keyboard) is disabled automatically.

Some laptops combine the S/PDIF jack with the headphone jack.

Audio jacks, such as those shown in Figure 11.17, are usually clearly labeled and are frequently located on the side panel of a laptop computer to make connecting speakers or a microphone easier than on a desktop computer (where these jacks are at the back of the computer). However, it's still possible to plug the wrong cable into a jack. One of the most common reasons a laptop fails to play any sound through external speakers is that the speakers are plugged into the wrong socket. To avoid this problem, some laptops color-code the jacks according to specifications found in the PC99 Design Guide (see www.pcdesguide.org/documents/pc99icons.htm). The color -coding can vary on some audio adapters (or not be present at all). The colors listed above for the audio jacks are those specified by the PC99 Design Guide.

Volume Control

With virtually all recent laptops with onboard sound, the volume is controlled through a Windows Control Panel speaker icon that can also be found in the system tray (near the onscreen clock). If you plug in external speakers, a headset, or use the digital audio (S/PDIF) option found on some recent laptops, you will need to use the mixing options in the volume control to select the proper sources and appropriate volume levels for incoming and outgoing audio. In Windows , use the Control Panel Sounds or Sounds and Audio Devices icon to adjust speaker type or make other advanced adjustments (see Figure 11.18)

Figure 11.18. Selecting the speaker type in Windows XP.

Keep in mind that if you are sending sound to an external audio receiver with either the normal speaker out or S/PDIF digital audio jacks, you need to adjust the volume on that device as well.

By contrast, some older laptops include a thumbwheel volume control next to the input/output jacks as well as the Windows Control Panel icon. The volume wheel can be troublesome ; if you aren't aware of its existence and it is turned all the way down, you might be puzzled by the adapter's failure to produce sufficient sound.

If you connect your laptop to external, amplified speakers but you aren't hearing any sound, remember to check that the power to the speakers is on, the volume control on the speakers is turned up, and the correct speakers are selected and properly connected to your laptop.

Laptop Audio Quality Factors

Whether you use your laptop's built-in audio to create or play back existing audio, you should consider the impact of factors such as the following:

• Audio data compression

• 3D audio acceleration

• Audio drivers

• DVD audio playback options

• Speaker types

• Hardware upgrades

See the following sections for details.

Audio Data Compression

Virtually all audio adapters on the market today can easily produce CD-quality audio, which is sampled at 44.1KHz. At this rate, recorded files (even of your own voice) can consume more than 10MB for every minute of recording. To counter this demand for disk space, many audio adapters include their own data-compression capability.

Most manufacturers of audio adapters use an algorithm called adaptive differential pulse code modulation (ADPCM) compression (it's also called IMA-ADPCM), which was developed by the Interactive Multimedia Association (IMA) to reduce file size by more than 50%. IMA-ADPCM compresses 16-bit linear samples down to 4 bits per sample. However, a simple fact of audio technology is that when you use such compression, you lose sound quality. Unfortunately, no standard exists for the use of ADPCM. For example, although both Apple and Microsoft support IMA-ADPCM compression, they implement it in different ways. Apple's standard AIFF and Microsoft's standard WAV file formats are incompatible with each other unless you use a media player that can play both.

Several codecs (programs that perform compression and decompression ) are installed to support the audio chip or integrated audio solution used by your laptop. Typically, some form of ADPCM is installed along with many others. To see which codecs are available on your system, open the Windows Control Panel and open the Multimedia icon (Windows 9x), the Sounds and Multimedia icon (Windows 2000), or the Sounds and Audio Devices icon (Windows XP). In Windows 9x, click the Devices tab followed by the plus sign next to Audio Compression to see the installed codecs. In Windows 2000 and Windows XP, click the Hardware tab, followed by Audio Codecs and Properties. The codecs are listed in order or priority, highest to lowest . You can also change the priority if you prefer a different order.

Note

If you create your own recorded audio for use on another computer, both computers must use the same codec. You can select which codec you want to use for recording sounds with most programs, including the Windows Sound Recorder.

The most popular compression standard is the Motion Pictures Experts Group (MPEG) standard, which works with both audio and video compression and is gaining support in the non-PC world for products such as DVD players. MPEG by itself provides a potential compression ratio of 30:1, and largely because of this, full-motion-video MPEG DVD and CD-ROM titles are now available. The popular MP3 sound-compression scheme is an MPEG format, and it can be played back on recent versions of the Windows Media Player, as well as by various other audio player programs and devices.

3D Audio and Laptops

Most recent laptops feature some type of 3D audio that works along with 3D graphics to provide more realistic gameplay. However, there are two methods used to provide 3D audio support:

• Hardware acceleration (audio chip based)

• Software/driver support

If you want to use your laptop to play 3D games , look for a model that features a discrete graphics chip with 3D support and an audio chip with 3D audio acceleration. Although laptop vendors prominently display the names of the discrete 3D graphics chips they use in their advertisements, you might need to look very carefully at the detailed specifications for a particular laptop to determine the type of audio it uses. Keep in mind that laptops that use integrated graphics usually feature integrated audio as well. Integrated audio, like integrated graphics, is usually not as fast, particularly for 3D and gaming uses.

Some of the major 3D audio features affected by the type of audio chip used in a particular laptop include the following:

• Support for positional audio

• Hardware versus software processing of 3D audio

• DirectX support issues

Positional Audio

The underlying issue common to all 3D sound cards is that of positional audio, which refers to adjusting features such as reverberation, balance, and apparent sound "location" to produce the illusion of sound coming from in front of, beside, or even behind the user. One very important element in positional audio is HRTF (Head Related Transfer Function), which refers to how the shape of the ear and the angle of the listener's head changes the perception of sound. Because HRTF factors mean that a "realistic" sound at one listener's head angle might sound artificial when the listener turns to one side or the other, the addition of multiple speakers that "surround" the user , as well as sophisticated sound algorithms that add controlled reverberation to the mix, are making computer-based sound more and more realistic.

The major standards for positional audio today include Creative's EAX (Environmental Audio Extensions) and Sensaura's Virtual Ear. If your laptop's audio chip supports either positional audio standard, your audio driver's properties sheets might offer options for adjusting speaker position and the acoustic environment (simulates acoustics in different room types) among others.

3D Audio Processing

A second issue for game players is how the laptop's audio chip produces 3D audio. As with 3D video, there are two major methods:

• Host-based processing (which uses the CPU to process 3D, which can slow down overall system operation)

• Processing on the audio adapter (referred to as 3D acceleration )

Most laptops use audio chips, which use the CPU for part of the audio processing task. If your laptop has a processor under 1GHz, host-based audio processing can cause major drops in frame rate, whereas onboard 3D audio processing maintains stable frame rates.

Even though most recent laptops have processors running at speeds well in excess of 1GHz (2GHz speeds and faster are becoming commonplace), the number of audio streams supported by 3D hardware acceleration varies greatly by chip and can be limited by problems with software drivers. For the best 3D audio acceleration, I recommend you do the following:

• Download and install the latest drivers for your laptop's audio solution

• Look for laptops that use high-performance audio chips

• Look for laptops with the fastest processors you can afford

To learn more about specific 3D audio chips used on recent laptops, see "Who's Who in Laptop Audio" in this chapter.

DirectX and Audio Adapters

Microsoft's DirectX is a series of application programming interfaces (APIs) that sit between multimedia applications and hardware. Unlike MS-DOS applications, which required developers to develop direct hardware support for numerous models and brands of audio cards, video cards, and game controllers, Windows uses DirectX to "talk" to hardware in a more direct manner than normal Windows drivers do. This improves program performance and frees the software developer from the need to change the program to work with different devices. Instead, a game developer only needs to work with the DirectX sound engine, DirectX 3D renderer, and DirectX modem or network interface routines.

Thanks to DirectX, sound card and chipset developers are assured that their products will work with recent and current versions of Windows.

DirectX Support Issues

The latest version of DirectX, DirectX 9, is designed to give all sound chips with 3D support a major boost in performance. Previous versions of DirectX supported 3D with DirectSound3D, but the performance of DirectSound3D was limited. Game programmers needed to test the audio adapter to see whether it supported DirectSound3D acceleration and then would either enable or disable 3D sounds based on the host hardware. Starting with DirectX 5.0, DirectSound3D works with third-party 3D acceleration features. Compared to DirectX 8, DirectX 9 improves 3D audio quality and performance. You can download it from the Microsoft DirectX Web site at www.microsoft.com/windows/directx.

Sound Drivers

As with many PC components , a software driver provides a vital link between an audio chip and the application or operating system that uses it. Operating systems such as Windows 9x/Me and Windows 2000/XP include a large library of drivers for most of the audio chips on the market (Windows NT 4.0 also supports some sound hardware but not as much as other versions of Windows). In most cases, these drivers are written by the manufacturer of the audio chip and distributed only by Microsoft. Keep in mind that some audio chip drivers for laptops are modified to meet the requirements of the laptop builder, so it's safer to get updates from the laptop vendor than from other sources.

Any DOS applications you might still use do not typically include as wide a range of driver support as an operating system, but you should find that most games and other programs support the Sound Blaster adapters. Typical laptop audio chips are Sound Blaster-compatible, so you should have no trouble finding driver support for all your applications.

If your game program locks up when you try to detect the sound card during configuration, set the card type and settings manually. This is often a symptom of inadequate emulation for Sound Blaster by a third-party card. If you have problems, check the game developer's or audio adapter's Web site for patches or workarounds.

DVD Movies on the Road

You don't need a dedicated DVD player to enjoy the clarity, control, extra features, and excitement of DVD movies.

Many laptops now feature DVD-ROM or combo CD-RW/DVD-ROM drives. These drives help bring the DVD movie experience to your laptop, but having a DVD-ROM and a DVD movie player program is only part of what you need to bring the big screen to your laptop.

To get the most out of your laptop DVD experience, you need the following:

• DVD playback software that supports Dolby Digital 5.1 or better output One of the best choices is Cyberlink's PowerDVD 5.x, available from www.gocyberlink.com.

• An audio adapter that will output to Dolby Digital 5.1compatible audio hardware If your laptop supports S/PDIF digital audio output (either from the laptop itself or by way of a docking station or port replicator), purchase the accessory needed to add S/PDIF output to your system. Note that the proprietary S-Video cable used by some Dell models also supports S/PDIF output. For laptops which lack a manufacturer-supplied digital audio output option, use the Creative Labs Sound Blaster Extigy. For more information, see "Upgrading Audio Output" later in this chapter.

• Dolby Digital 5.1compatible stereo receiver and speakers Use the appropriate type of stereo receiver for your sound hardware. If your system supports S/PDIF digital audio, use a digital speaker system. The Creative Labs Extigy external audio processor can attach to both analog and digital 5.1 speaker systems.

To learn more about speaker terminology and how to ensure your speaker configuration is correct, see the section "Speakers," later in this chapter.

Playing and Creating Digitized Sound Files

You can use two basic types of files to store audio on your laptop. One type is generically called a sound file and uses formats such as WAV, VOC, AU, and AIFF. Sound files contain waveform data, which means they are analog audio recordings that have been digitized for storage on a computer. Just as you can store graphic images at different resolutions, you can have sound files that use various resolutions , trading off sound quality for file size. The default sound-resolution levels used in Windows are shown in Table 11.14.

Table 11.14. Windows Default Sound File Resolutions

Resolution	Frequency	Bandwidth	Data Rate (number of KB per second of audio stored)
Telephone quality	11,025Hz	8-bit mono	11KBps
Radio quality	22,050Hz	8-bit mono	22KBps
CD quality	44,100Hz	16-bit stereo	172KBps

If you have audio hardware that supports DVD-quality sound (48,000Hz, 16-bit stereo, 187KBps), you can also save sounds at that frequency, but you must select it manually if you are using the Windows Sound Recorder to digitize sounds. Note that the Windows Sound Recorder applet uses the default Pulse Code Modulation (PCM) method for storing sounds. PCM produces the highest quality of sound, but because it doesn't use any type of data compression, file sizes can be enormous .

As you can see, the difference in file sizes between the highest and lowest audio resolution levels is substantial. CD-quality sound files can occupy enormous amounts of disk space. At this rate, just 60 seconds of audio would require more than 10MB of storage. For applications that don't require or benefit from such high resolution, such as voice annotation, telephone-quality audio is sufficient and generates much smaller files. To achieve a balance between high quality and smaller file sizes, you can convert conventional WAV files into compressed formats, such as MP3 or WMA audio files.

The other type of file is a MIDI file, which consists of a musical score that is played back by synthesized or sampled musical instruments incorporated into the sound card's MIDI support.

On a multimedia PC, it is often possible for two or more sound sources to require the services of the audio adapter at the same time. Any time you have multiple sound sources you want to play through a single set of speakers, a mixer is necessary.

Most laptops with onboard sound include a mixer that enables all the different audio sources, MIDI, WAV, line-in, and CD, to use the single line-out jack. Starting with Windows 95 through the latest Windows versions (XP Pro/XP Home), Windows uses a single mixer for both recording and playback features, instead of using separate mixers as with Windows 3.x. Normally, the system ships with software that displays visual sliders like you would see on an actual audio mixer in a recording studio. With these controls, you can set the relative volume of each of the sound sources.

Tip

Whenever you change from analog to digital speakers or add speakers to a two-speaker configuration, you must adjust the mixer controls to match your current speaker configuration. If you don't, you will be unable to hear anything through your speakers.

Audio Adapter Concepts and Terms

To fully understand audio adapters and their functions, you need to understand various concepts and terms, such as 16-bit, CD quality, and MIDI port, to name just a few. Concepts such as sampling and digital-to-audio conversion (DAC) are often sprinkled throughout stories about new sound products. You've already learned about some of these terms and concepts; the following subsections describe many others.

The Nature of Sound

To understand an audio adapter, you must understand the nature of sound. Vibrations that compress air or other substances produce every sound. These sound waves travel in all directions, expanding in balloon-like fashion from the source of the sound. When these waves reach your ear, they cause vibrations that you perceive as sound.

Two of the basic properties of any sound are its pitch and intensity.

Pitch is the rate at which vibrations are produced. It is measured in the number of hertz (Hz), or cycles per second. One cycle is a complete vibration back and forth. The number of Hz is the frequency of the tone; the higher the frequency, the higher the pitch.

Humans can't hear all possible frequencies. Very few people can hear sounds with frequencies less than 16Hz or greater than about 20KHz (kilohertz; 1KHz equals 1,000Hz). In fact, the lowest note on a piano has a frequency of 27Hz, and the highest note has a frequency a little higher than 4KHz. Frequency-modulation (FM) radio stations can broadcast notes with frequencies as high as 15KHz.

The amazing compression ratios possible with MP3 files, compared to regular CD-quality WAV files, is due in part to the discarding of sound frequencies that are higher or lower than normal hearing range during the ripping process.

The intensity of a sound is called its amplitude . This intensity determines the sound's volume and depends on the strength of the vibrations producing the sound. A piano string, for example, vibrates gently when the key is struck softly. The string swings back and forth in a narrow arc, and the tone it sends out is soft. If the key is struck more forcefully , however, the string swings back and forth in a wider arc, producing a greater amplitude and a greater volume. The loudness of sounds is measured in decibels (db). The rustle of leaves is rated at 20db, average street noise at 70db, and nearby thunder at 120db.

Evaluating the Quality of Your Audio Adapter

The quality of an audio adapter is often measured by three criteria: frequency response (or range), total harmonic distortion, and signal-to-noise ratio.

The frequency response of an audio adapter is the range in which an audio system can record or play at a constant and audible amplitude level. Many cards support 30Hz20KHz. The wider the spread, the better the adapter.

The total harmonic distortion (THD) measures an audio adapter's linearity and the straightness of a frequency response curve. In layman's terms, the harmonic distortion is a measure of accurate sound reproduction. Any nonlinear elements cause distortion in the form of harmonics. The smaller the percentage of distortion, the better. This harmonic distortion factor might make the difference between cards that use the same audio chipset. Some audio chips might have greater distortion, making them produce poorer-quality sound.

The signal-to-noise ratio (S/N or SNR) measures the strength of the sound signal relative to background noise (hiss). The higher the number (measured in decibels), the better the sound quality.

These factors affect all types of audio use, from WAV file playback to speech recognition. Keep in mind that low-quality microphones and speakers can degrade the performance of a high-quality audio chip.

Note

If audio quality becomes the deciding factor between two similar laptops, determine what audio chip the laptops use and check the audio chip vendors' Web sites to determine the frequency response, THD, and SNR values for the audio chips used by the laptops you are considering. If you are planning to add an external audio device such as a Sound Blaster MP3+ or Sound Blaster Audigy, be sure to compare its values to the built-in audio chip. In most cases, external devices have better-quality output than built-in audio.

Sampling

With an audio chip, a laptop can record waveform audio. Waveform audio (also known as sampled or digitized sound ) uses the PC as a recording device (like a tape recorder). Small computer chips built in to the adapter, called analog-to-digital converters (ADCs) , convert analog sound waves into digital bits that the computer can understand. Likewise, digital-to-analog converters (DACs) convert the recorded sounds to an audible analog format. Although chipmakers still produce ADC and DAC chips, these functions are incorporated into the single-chip audio solutions found in laptop computers.

Sampling is the process of turning the original analog sound waves into digital (binary) signals that the computer can save and later replay (see Figure 11.19). The system samples the sound by taking snapshots of its frequency and amplitude at regular intervals. For example, at time X the sound might be measured with an amplitude of Y. The higher (or more frequent) the sample rate, the more accurately the digital sound replicates its real-life source and the larger the amount of disk space needed to store it.

Figure 11.19. Sampling turns a changing sound wave into measurable digital values.

Originally, audio chips used 8-bit digital sampling, which provided for only 256 values (2 ⁸ ), to convert a sound. More recently, audio chips have increased the quality of digitized sound by using 16-bit (2 ¹⁶ ) sampling to produce 65,536 distinct values. Today's highest-quality audio chips feature 24-bit sampling (2 ²⁴ ), which translates into more than 16.8 million possible digital values that can be matched to a given sound.

You can experiment with the effects of various sampling rates (and compression technologies) by recording sound with the Windows Sound Recorder or a third-party application set to CD-quality sound. Save the sound and play it back at that highest quality setting. Then convert the file to a lower quality setting, and save the sound file again with a different name. Play back the various versions, and determine the lowest quality (and smallest file size) you can use without serious degradation to sound quality.

Who's Who in Laptop Audio

As you've learned in other chapters, I believe it is very important to get all the technical information you can about your computer and its components. By knowing who makes the audio chip your computer depends on, you can find out what the hardware can do and be better able to find upgrades to the software drivers you need to get the most out of your audio hardware.

The following companies are the major providers of audio chips for recent and current laptop computers:

• Analog Devices

• Cirrus Logic/Crystal Semiconductors

• C-Media Electronics

• ESS Technology

• Realtek

Their product lines are covered in greater detail in the following sections.

Note

Most recent laptops use audio chips that provide up to six-channel output. However, unless the laptop can be plugged into an S/PDIF cable or into a docking station or port replicator with six-channel output, you will get only stereo sound from the basic audio outputs on the laptop itself.

Analog Devices

Analog Devices is the current market leader among sound chip makers , offering a range of audio chips and software under the SoundMAX trade name. Analog Devices' audio chips correspond to the AC '97 audio standard and include the AD1885, AD1981 series, AD1980, and AD1985 models, all of which can support up to six-channel audio. For more information about these chips, see the SoundMAX Web site at www.soundmax.com.

ESS Technology, Inc.

ESS Technology provides audio and combo audio/modem/network chips for several different brands and models of notebook computers. ESS Technology's chips include the Maestro, Allegro, Canyon3D, and other chips in the ES19xx and ES1xxx series. For more information about ESS chipsets, see the ESS Web site at www.esstech.com.

Creative Labs

Creative Labs introduced its EV1938 and EV1958 in 1999, and they have been adopted by some laptop makers. The EV1938 chip is based on the SoundBlaster Audio PCI 64V. The EV1958 chip is based on the SoundBlaster Audio PCI 128. For more information about Creative Labs chipsets, see the Creative Labs Web site at www.creative.com.

Creative Labs also makes the Extigy and USB Sound Blaster MP3+ external digital music processors for laptops and desktops. See "Upgrading Audio Output" in this chapter.

Cirrus Logic

Cirrus Logic offers a wide range of sound chips, with the most common on recent laptops being the CS4205 AC '97 codec. Cirrus Logic also uses the Crystal brand name on some of its audio chip lines. For more information on Cirrus Logic and Crystal audio chips, see the Cirrus Logic Web site at www.cirrus.com.

C-Media

C-Media produces a variety of sound chips, with the most common on recent laptops being the CMI9739A six-channel AC '97 codec. For more information on C-Media sound chips, see the C-Media Web site at www.cmedia.com.tw.

RealTek

RealTek produces a variety of sound chips that support the AC '97 codec. The ALC2xx series supports two-channel (stereo) output, whereas the ALC6xx series supports six-channel output. Both chip series are used in a variety of laptop computers. For more information about RealTek sound chips, see the RealTek Web site at www.realtek.com.tw.

AC '97 Integrated Audio

The phrase AC '97 has occurred repeatedly in the description of recent audio chip product lines. What exactly does it mean to you as a laptop computer user?

AC '97 (often referred to as AC97 ) is an Intel specification that connects an audio codec (compression/decompression) architecture to a section of a South Bridge or an I/O Communications Hub chip called the AC -Link control . The AC-Link control works with the CPU and an AC '97 digital signal processor (DSP) to create audio. Consequently, a laptop which uses AC '97 audio is using partially host-based audio. However, given the performance of recent mobile processors (1GHz to 2GHz and faster), this is not a major performance issue for most users.

The AC '97 audio codec can be implemented in various ways. Laptops typically implement it with a physical chip on the motherboard, but sometimes with just a software program. Sometimes a laptop might also integrate an analog modem through an MC '97 codec chip, or it might have an AMC '97 (audio/modem) codec chip to combine both functions.

Your laptop vendor supplies the drivers for a particular AC '97 codec chip because they must be customized to the combination of codec and South Bridge/ICH chip your motherboard uses.

Although the AC '97 specification recommends a standard pinout, differences do exist among AC '97 codec chips. Some vendors of AC '97 chips provide technical information to help system standard builders design sockets that can be used with different models of the AC '97 codec chip.

The four versions of the AC '97 codec standard are as follows :

• AC '97 1.0 Has a fixed 48KHz sampling rate and stereo output.

• AC '97 2.1 Has options for variable sampling rate and multichannel output.

• AC '97 2.2 Has AC '97 2.1 features plus optional S/PDIF digital audio and enhanced riser card support. AC '97 2.2 was released in September 2000.

• AC '97 2.3 Has AC '97 2.1/2.2 features plus support for true Plug-and-Play detection of audio devices, which helps prevent accidentally connecting speakers to the microphone jack, and so on. AC '97 2.3 was released in July 2002.

Most laptops with integrated audio support AC '97 2.1 or greater at this time. However, a special audio cable or a docking station or port replicator with additional audio outputs is necessary to take advantage of the additional channels or S/PDIF digital output options provided by AC '97 2.1 and higher versions.

Note

To learn more about the AC '97 specifications, see Intel's Research and Development, Audio Codec site at www.intel.com/labs/media/audio/index.htm.

To determine whether a particular laptop's implementation of AC '97 audio will be satisfactory, follow these steps:

1. Determine which codec chip the laptop uses. Read the detailed specifications for the laptop, the laptop's instruction manual, or check the list of drivers to determine which chip the laptop uses for audio.

2. Look up the chip's features and specifications using the Web site information provided earlier in this chapter. If you are not sure of the chip manufacturer, look up the part number (if known) with a search engine such as Google.

3. Use a search engine to find reviews of the chip's sound quality and performance. Because desktop motherboards often use the same AC '97 chips that laptops use, you might find both laptop and desktop system or motherboard articles that contain a review of the chip.

4. Look at the laptop's features and optional equipment to determine whether it uses the full capabilities of the codec chip. Chips that support AC '97 2.1 can offer up to six-channel analog audio; those that support AC '97 2.2 or above can also offer S/PDIF digital audio. However, many laptops don't offer built-in outputs for these optional outputs. Check with your laptop vendor to determine if a special cable, docking station, or port replicator is available and provides the additional outputs needed.

Speakers

All laptops with integrated audio have built-in speakers. However, the sound quality and available volume of built-in speakers is often inadequate for high-quality music playback, MIDI work, multimedia applications, or business presentations before a large group. In these cases, you will want to attach more powerful and higher-quality speakers to your laptop's speaker jack. If your laptop has S/PDIF digital audio output, you will need to connect your laptop to a home theater system with an S/PDIF input to be able to play back digital audio from sources such as DVD movies. In either case, you should try to select the highest-quality speakers you can afford.

Note

To enjoy better sound quality in small meetings or for personal use, look for laptops that integrate high-quality speakers, such as the JBL Pro speakers found in some HP/Compaq models.

When you need to add external speakers, look for the best performance available in a small space. I recommend small bookshelf speakers instead of standard stereo speakers, especially if you must travel with the speakers.

You should not depend on the onboard audio system in your notebook to provide adequate amplification. Instead, use self- powered , magnetically shielded speakers. Magnetic shielding is especially important if you are using a CRT monitor along with your laptop in a business presentation. Unshielded speakers near the CRT can create magnetic interference, which can distort colors and objects onscreen or jumble the data recorded on nearby floppy disks or other magnetic media.

Caution

Although most computer speakers are magnetically shielded, do not leave recorded tapes, watches , credit cards, or floppy disks in front of the speakers for long periods of time.

With dozens of brands and models on the market at a variety of price points, it's essential to understand how to evaluate the quality of any given speaker. Speakers are measured by three criteria:

• Frequency response A measurement of the range of high and low sounds a speaker can reproduce. The ideal range is 20Hz20KHz, the range of human hearing. No speaker system reproduces this range perfectly . In fact, few people hear sounds above 18KHz. An exceptional speaker might cover a range of 30Hz23,000Hz, and lesser models might cover only 100Hz20,000Hz. Frequency response is the most deceptive specification because identically rated speakers can sound completely different.

• Total Harmonic Distortion (THD) An expression of the amount of distortion or noise created by amplifying the signal. Simply put, distortion is the difference between the sound sent to the speaker and the sound you hear. The amount of distortion is measured in percentages. An acceptable level of distortion is less than .1% (one-tenth of 1%). For some CD-quality recording equipment, a common standard is .05%, but some speakers have a distortion of 10% or more. Headphones often have a distortion of about 2% or less.

• Watts Usually stated as watts per channel , this is the amount of amplification available to drive the speakers. Check that the company means "per channel" (or RMS) and not total power. Many audio adapters have built-in amplifiers, providing up to 8 watts per channel (most provide 4 watts). This wattage is not enough to provide rich sound, however, which is why many speakers have built-in amplifiers . With the flick of a switch or the press of a button, these speakers amplify the signals they receive from the audio adapter. If you do not want to amplify the sound, you typically leave the speaker switch set to "direct." In most cases, you'll want to amplify the signal.

Inexpensive PC speakers sometimes use batteries to power the amplifiers. Because these speakers require so much power, you might want to invest in an AC adapter or purchase speakers that use AC power. With an AC adapter, you won't have to buy new batteries every few weeks. If your speakers didn't come with an AC adapter, you can pick one up from your local Radio Shack or hardware store. Be sure that the adapter you purchase matches your speakers in voltage and polarity; most third-party adapters are multiple voltage, featuring interchangeable tips and reversible polarity.

You can control the volume and other sound attributes of your speakers in various ways, depending on their complexity and cost. Typically, each speaker has a volume knob, although some share a single volume control. If one speaker is farther away than the other, you might want to adjust the volume accordingly . Many computer speakers include a dynamic bass boost (DBB) switch. This button provides a more powerful bass and clearer treble, regardless of the volume setting. Other speakers have separate bass and treble boost switches or a three- band equalizer to control low, middle, and high frequencies. When you rely on your audio adapter's power rather than your speakers' built-in amplifier, the volume and dynamic bass boost controls have no effect. Your speakers are at the mercy of the adapter's power.

For best audio quality, adjust the master volume on the sound card near the high end and use the volume control on powered speakers to adjust the volume. Otherwise, your speakers will try to amplify any distortions coming from the low-power input from the PC's audio adapter.

An 1/8'' stereo minijack connects from the audio adapter's output jack to one of the speakers. The speaker then splits the signal and feeds it through a separate cable from itself to the second speaker (often referred to as the satellite speaker ).

Before purchasing a set of speakers, check that the cables between the speakers are long enough for your computer setup.

Beware of speakers that have a tardy built-in sleep feature. Such speakers, which save electricity by turning themselves off when they are not in use, might have the annoying habit of clipping the first part of a sound after a period of inactivity.

Speakers that are USB-based will not be capable of playing CD music unless the CD-ROM drive can perform digital audio extraction. Check your drive's specifications for information.

Headphones are an option when you can't afford a premium set of speakers. Headphones also provide privacy and enable you to play your PC audio as loud as you like.

For best results with laptops that support four speakers or more, check the properties sheet for the audio adapter and set whether you're using headphones, stereo speakers, or a larger number of speakers.

Make sure that speakers are placed properly. If you use a subwoofer , put it on the floor for better bass sound and to reduce EMI interference with other devices.

Upgrading Audio Output

If you're a serious gamer or DVD movie lover, you won't be content with ordinary stereophonic sound from your laptop, especially if it is your only computer. Traditionally, if you wanted to move to more elaborate speaker setups or enjoy Dolby Digital output support, you could choose from these options:

• Connect a special cable with optical output to your laptop

• Connect your laptop to a docking station or port replicator that features optical or multichannel output

However, if your laptop doesn't provide these options, you're no longer stuck with standard stereo output.

Creative Labs (www.soundblaster.com) makes two external Sound Blaster units that can be plugged into any laptop's USB ports (including those which don't have onboard audio) to provide better sound quality and output options:

• Sound Blaster MP3+

• Sound Blaster Extigy

Sound Blaster MP3+

Sound Blaster MP3+ is a compact self-contained unit that is powered by your laptop's USB port (see Figure 11.20). Although it supports only analog or digital stereo speakers with optional subwoofer (2.1 speaker configuration), it offers several features to enhance stereo sound output:

• Bass boost

• Audio cleanup to improve playback of MP3 files made from older analog sources

• Ten-band graphic equalizer

• Smart volume management to equalize volume during playback of digital audio from different sources

• Virtual surround sound and EAX effects

• Works with headsets or external speakers

Figure 11.20. Front (top) and rear (bottom) views of the Creative Labs Sound Blaster MP3+. It can be used with both laptop and desktop PCs as well as with MP3 players and other types of portable music systems. (Photos courtesy Creative Labs.)

Sound Blaster Extigy

Sound Blaster Extigy also connects to any laptop's USB port (but requires its own AC power supply) and offers these features:

• Signal-to-noise ratio (SNR) exceeding 100db for hiss-free sound.

• Broad frequency response range and dynamic range exceeds most onboard audio.

• Low total harmonic distortion and noise (THD+N) value below most onboard audio.

• 24-bit digital sampling at 48KHz for analog input and 24-bit/96KHz output, compared to 16-bit sampling at 48KHz for most onboard sound chips.

• S/PDIF digital input and output.

• Support for simultaneous playback of 5.1 audio and Dolby Digital audio.

• Built-in Dolby Digital (AC-3) decoder supports DVD players and home-theater systems in both PC-connected and standalone modes and DVD player software when connected to a PC or laptop.

• CMSS converts stereo sound into 5.1-compatible sound, as desired.

• EAX environmental audio.

• Analog speaker support for 2, 4, and 5.1 speakers; S/PDIF optical and coaxial input and output jacks; microphone in, line in, and headphone out jacks; and MIDI input and output jacks.

• Remote control for adjusting audio playback and other features.

As you can see, the Sound Blaster Extigy is designed to provide a huge audio upgrade for any laptop (or desktop PC) with a USB port (see Figure 11.21).

Figure 11.21. Front (top) and rear (bottom right) views of the Creative Labs Sound Blaster Extigy. The inset at lower left shows the optical S/PDIF ports on the front of the unit. (Photos courtesy Creative Labs.)

Tip

Extigy works best when it is plugged into a nonshared USB 1.1 root hub (there are two USB ports per root hub) because of the bandwidth it requires. A USB 2.0 (Hi-Speed USB) port is also a good choice if you have a mixture of USB 1.1 and Hi-Speed USB ports on your laptop.

Speaker and System Configuration

To ensure you get the sound you expect from four or more speakers, check the following:

• Use the properties sheet for your audio chip to properly describe your speaker setup This includes selecting the number of speakers you are using, setting options for 3D environmental audio and positional sound such as reverb, and setting up your subwoofer if present.

• Make sure you use the correct cabling between your speakers and laptop or external audio device If you are planning to use an AC3/Dolby speaker setup, such as 4.1 or 5.1, be sure you use the correct S/PDIF connection and configuration. This varies from system to system; check the vendor's Web site for details.

• Make sure you have placed your speakers correctly In some cases you can adjust the audio adapter's properties to improve sound quality, but sometimes you might need to move the speakers themselves.

• Make sure you have connected your speakers to the proper jacks Mixing up left and right or front and rear causes poor sound quality.

Typical Speaker Setups

The simplest audio configuration available today is stereo, which uses two speakers placed to overlap sound. In a two-channel setup, the two speakers are referred to as left and right ( L and R in Figure 11.22).

Figure 11.22. 2.1 (left) and 4.1 (center) speaker setups compared to a 5.1 speaker setup (right). The subwoofer (S) is independently controlled only in the 5.1 configuration.

Some laptops now support at least four speakers, but depending on the laptop's audio chip, settings, and sound output options in the program, the rear speakers might simply mirror the front speakers' output, or you might have four distinct sound streams. In a four-point setup, the two front speakers become front left and front right (FL and FR), whereas the back speakers are rear left and rear right (RL and RR).

Four-point surround sound uses four speakers plus a subwoofer ( S , in Figure 11.22) to surround you with music and gaming sound effects; the four speakers are placed around the listener, and the subwoofer is usually placed near a wall or in the corner to amplify its low-frequency sound. The subwoofer in such a setup is not on a separate circuit but is controlled by the same signals sent to the other speakers.

On the other hand, 5.1 Surround sound, also referred to as Dolby Digital or DTS Surround sound (when digital speakers are used) uses five speakers plus a subwoofer. The fifth speaker is placed between the front two speakers as the center channel ( C , in Figure 11.22) to provide most of the vocal audio. The subwoofer is independently controlled. This is the preferred sound system for use with DVD movies. Figure 11.22 compares typical 2.1, 4.1, and 5.1 speaker setups.

Generally, on any laptop with an audio chip, you should have a speaker icon in the Windows system tray. If the speaker icon (indicating the Volume Control) isn't visible, you can install it through the Control Panel's Add/Remove Programs icon. With Windows 9x/Me, select the Windows Setup tab and open the Multimedia section. Then, check the box labeled Volume Control. With Windows XP, open the Sounds and Audio Devices icon in Control Panel, click the Volume tab, and click the Place Volume icon in the taskbar box. In some cases you might be asked to insert the Windows CD-ROM if additional drivers are required to complete the installation.

If you use digital sound sources or output such as Dolby 5.1, CD digital, or S/PDIF, open the properties sheet for your mixer device and enable display of these volume controls.

Use the Volume Control to ensure your speakers are receiving a sound signal. The mixer sometimes defaults to Mute. You can usually adjust volume separately for wave (WAV) files, MIDI, microphone, and other components.

Microphones

If you don't want to use the microphone built in to the laptop for speech recognition, for computer telephony, or to record your voice to a WAV file, you'll need to add a microphone. Finding a compatible microphone is quite simple. You need one that has an 1/8'' minijack to plug into your laptop's microphone, or audio-in, jack. Hand-held microphones have an on/off switch, but microphones built in to headsets or boom microphones usually don't.

Like speakers, microphones are measured by their frequency ranges. This is not an important buying factor, however, because the human voice has a limited range. If you are recording only voices, consider an inexpensive microphone that covers a limited range of frequencies. An expensive microphone's recording capabilities extend to frequencies outside the voice's range. Why pay for something you won't need?

If you are recording music, invest in an expensive microphone, but be sure your audio chip can do justice to the signal produced by the microphone.

Your biggest decision is to select a microphone that suits your recording style. If you work in a noisy office, you might want a unidirectional microphone that will prevent extraneous noises from being recorded. An omnidirectional microphone is best for recording a group conversation.

This can be a small lapel microphone, a handheld microphone, or one with a desktop stand. If you want to keep your hands free, you might want to shun the traditional handheld microphone for a lapel or desktop model. If your audio adapter does not come with a microphone, see your local stereo or electronics parts store. Be sure that any microphone you purchase has the correct impedance to match the audio adapter's input.

If you're using voice-recognition software such as Dragon Naturally Speaking, IBM ViaVoice, or Philips FreeSpeech, use the microphone supplied with the software or choose from alternative models the software vendor recommends. Run the microphone setup program again if your software has trouble recognizing your voice. Some newer models feature a battery pack to boost sound quality; be sure to check the batteries and replace them to keep recognition quality high.

If you're talking but your voice-recognition or recording software isn't responding, check the following:

• Incorrect jack It's easy to plug the microphone into the wrong jack. Try using a magic marker to color-code the microphone wire and jack to make matching up easier.

• The recording volume in the mixer control This usually defaults to Mute to avoid spurious noise.

• Make sure the microphone is turned on in the voice-recognition or recording software You must click the Record button in recording software, and many voice-recognition programs let you "pick up" the microphone for use or "put it down" when you need to answer the phone. Look for an onscreen microphone icon in the Windows System Tray for fast toggling between modes.

Troubleshooting Laptop Audio Problems

To operate , an audio chip needs hardware resources, such as IRQ numbers , a base I/O address, and DMA channels that don't conflict with other devices. Fortunately, the combination of laptop hardware which is preconfigured to work together and the use of Plug-and-Play hardware for the audio chip and the PC Card/CardBus slots have made resource conflicts practically unheard of in recent laptops.

However, it's still possible to have problems with laptop audio, which are usually due to other factors. Use the following sections to help your laptop to produce the best audio recording and playback results.

No Sound from Internal Speakers

If you don't hear anything from your laptop's speakers, consider these solutions:

• Make sure the audio chip is working correctly and does not have any driver or other problems. Use the Windows Device Manager to check for problems and solutions.

• Are the mixer settings correct? Many audio adapters include a sound mixer application. The mixer controls the volume settings for various sound devices, such as the microphone or the CD player. There might be separate controls for both recording and playback. Increase the master volume or speaker volume when you are in the play mode.

• Is the Mute option selected? If the Mute option is selected in your sound mixer software, you won't hear anything.

• Are the speakers turned down with external controls? Some older laptops use a thumbwheel to adjust volume, whereas newer models sometimes use pushbuttons near the keyboard.

• If your computer game lacks sound, check that it is designed to work with your audio adapter. For example, some legacy and early Windows games might require the exact settings of IRQ 7 (or IRQ 5), DMA 1, and I/O address 220 to be Sound Blaster compatible.

Sound Problems with External Speakers

If you don't hear anything from external speakers, consider these solutions:

• What type of speakers are you using? Depending on the speaker type and sound source type, you might need to switch from analog to digital sound for some types of sound output. Make sure that the correct digital audio volume controls are enabled in your audio device's mixer control.

• Are the speakers connected? Check that the speakers are plugged into the sound card's stereo line-out or speaker jack (not the line-in or microphone jack).

• Are the speakers receiving power? Check that the power "brick" or power cord is plugged in securely.

• Are the speakers stereo? Check that the plug inserted into the jack is a stereo plug, not mono.

If you hear sound coming from only one speaker, check out these possible causes:

• Are you using a mono plug in the stereo jack? A common mistake is to use a mono plug in the laptop's audio speaker or stereo-out jacks. Seen from the side, a stereo connector has two darker stripes . A mono connector has only one stripe.

• If you're using amplified speakers, are they powered on? Check the strength of the batteries or the AC adapter's connection to the electrical outlet. If each speaker is powered separately, be sure that both have working batteries.

• Are the speakers wired correctly? When possible, use keyed and color-coded connectors to avoid mistakes.

• Are both speakers set to the same volume? Some speakers use separate volume controls on each speaker. Balance them for best results. Separate speaker volume controls can be an advantage if one speaker must be farther away from the user than the other.

• Is the speaker jack loose? If you find that plugging your speaker into the jack properly doesn't produce sound but pulling the plug half-way out or "jimmying" it around in its hole can temporarily correct the problem, you're on the road to a speaker jack failure. To avoid damage to the speaker jack, be sure you insert the plug straight in, not at an angle.

If you can barely hear audio, try these solutions:

• Are the speakers plugged into the proper jack? Speakers require a higher level of drive signal than headphones. Again, adjust the volume level in your mixer application.

• Are the mixer settings too low? Again, adjust the volume level in your mixer application. If your mixer lets you choose between speakers and headphones, be sure to select the correct speaker configuration.

• Are the speakers too weak? Some speakers might need more power than your audio adapter can produce. Try other speakers or put a stereo amplifier between your sound card and speakers.

Scratchy Sound

Scratchy or static-filled sound can be caused by several problems. Improving the sound can be as simple as rearranging your hardware components. The following list suggests possible solutions to the problem of scratchy sound:

• Are your speakers too close to an external CRT monitor? The speakers can pick up electrical noise from your monitor. Move them farther away. Subwoofers should never be placed near a CRT monitor because their powerful magnets can interfere with the picture. They should be on the floor to maximize low-frequency transmission.

• Are you experiencing compatibility problems between particular games and your sound card? If you notice sound problems such as stuttering voices and static on some games but not others, check with the game vendor for a software patch or with the sound card vendor for updated drivers. If the game uses DirectX, run the DXDIAG diagnostics program (select Start, Run; type DXDIAG ; and click OK) and click the Sound tab. Adjust the slider for Hardware Sound Acceleration Level down one notch from Full (the default) to Standard, click Save All Information, and exit. Retry the game. If the problem persists, adjust the Hardware Sound Acceleration Level setting to Basic. If other games have performance problems after you adjust the Hardware Sound Acceleration Level, be sure to reset it to Full before playing those games.

Advanced Features

If you are having problems playing DVD audio, playing MP3 files, or using S/PDIF connections, make sure of the following:

• You are using the correct playback program.

• Your mixer has the correct volume control setting for the device.

• Your cabling is correct for the device.

Other Problems

Sometimes sound problems can be difficult to solve. A good way to solve problems of all types with Plug-and-Play devices such as onboard audio, a PnP BIOS, and a PnP operating system (Windows 9x/Me/2000/XP) is to use the Device Manager to remove the audio chip, restart the system, and allow the card's components to be redetected. This installs a "fresh" copy of the software and reinserts Registry entries.

If you are using a laptop with a VIA chipset, be sure to download and install the latest versions of VIA drivers.