STEP 03 optimizing audioNOISE GATES

The natural rhythm of speaking and reading often brings a fair number of pauses into a voiceover. Unless you are recording in a professional sound booth , you'll pick up a great deal of ambient noise during a pause. That ambient noise is distracting and always seems to get louder during MP3 (or ACDM, for that matter) encoding. Although it's possible to edit out all the pauses, that process tends to also remove the natural cadences of speechparticularly important in the example voiceover, a poem. A better solution for handling noise during pauses is to apply an effect known as a noise gate. A noise gate takes all sound below a set threshold and totally attenuates it, reducing the audio to silence. In SoundForge, you can set how fast the gate opens and closes , thus affecting how the sound fades out and back in on either side of the silenced portion. Again, applying a noise gate takes practice and experimentation to achieve the right effect without clipping the surrounding audio.

To apply a noise gate in SoundForge, follow these steps:

1. With the whole clip selected, choose Effects > Noise Gate.

2. Adjust the Threshold so that it is just below the maximum sample rate, as shown in figure 07:06.

   
   

   Figure 07:06.

   

   
   

   To find the maximum sample rate, choose a voiceless region in the waveform and select Tools > Statistics. Make note of the Maximum Sample Value; in the Noise Gate dialog, set the Threshold to a value a bit below the Maximum Sample Value.

3. If desired, enter new values for the Attack and Release times. What you want to end up with is simple; reduce the amount of low-level static and noise that occurs in the pauses between the reader speaking.

When it comes time to export the file as a .wav or .aif file, you might consider exporting it in pieces. For longer Flash movies, it's often easier to sync several different clips to onscreen imagery when working with sections. With the example file, I made an early decision to export it in four pieces. Why? With my recording, I felt it would be easier to work with and, with the use of the Smart Preload technique, better sync my audio to my visuals. Again, it all comes down to testing.