452 CHAPTER 12: Digital Audio: Providing Aural Feedback for UI Designs Using SoundPool
Underneath these are settings for speaker and microphone volume, as well as system audio setting
selector drop-downs. On the bottom of the Audacity window, you will find the project sample rate in
Hz and hours, minutes, seconds, and milliseconds displays, for Selection Start, End or Length, and
Audio Position, for micro-fine-tuning.
The first thing that you will want to do is to make sure your sample resolution and sample rate are
set correctly, before you start to export to the various digital audio formats that you have learned
about previously.
As you can see in Figure 12-6, the current sample rate is 48 kHz, which is high-quality and fine for
our use, but the sample resolution is 32-bit, which is twice the amount of data that we need to get a
great-quality sample data footprint result, regardless of the audio codec (format) that we use.
So our first step in our data footprint optimization work process is to change this raw audio sample
data format from 32-bit 48 kHz into a 16-bit 48 kHz raw audio sample data format. This will reduce
the amount of audio data going into the encoder (codec) by 100% right off the bat! You want to set
a reasonable 16-bit 48 kHz audio file baseline, so that you can see the actual compression result
that each audio codec can offer to the Android project. We will calculate this later as a percentage
by dividing the baseline uncompressed audio file size by the compressed audio file size to see how
many times, or what percentage, compression that codec is providing.
Figure 12-6. Audacity 2.0.5 main audio editor screen showing the stereo 32-bit floating-point 48 kHz sample data