Bits, hertz, bandwidth and mobile audio recording

I find this subject boring but important. So there you have it.

Here are some good links to information on choosing the right sampling rate for audio recordings:

http://audacityteam.org/wiki/index.php?title=Sample_Rates

http://www.cs.cf.ac.uk/Dave/Multimedia/node150.html

http://www.wisegeek.com/what-is-a-good-bitrate-guideline-for-mp3-files.htm

If you’re trying to get those blasted AMR files off your phone and into Audacity, this site can help: http://media-convert.com/

After playing around with various recording levels on my Zoom H2 and Nokia 5300, I can’t see any advantage of saving mp3s at a bit rate higher than 96. I saved a recording at 16, 32, 96 and 128 bits in mp3 format and the 32 bit was acceptable while the 96 was terrific. I could detect no difference between 96 and 128. I think for voice recordings 96 should be a good standard while you can compress audio to 32 for situations where it will be played through FM radio or on inferior sound equipment (read “most of the world”).

Here are the stats on a 32-second recording I made:

Bit rate	Size	Quality	Application
16	66K	Poor, grainy	Mobile download
32	140K	Slightly grainy	FM Radio
96	419K	Rich sound	mp3
128	558K	Equal to 96	CD

Here are three of the four recordings for your listening pleasure.

The poem is On a Fly Drinking Out of His Cup by William Oldys

On a Fly Drinking Out of His Cup 16.mp3

On a Fly Drinking Out of His Cup 32.mp3

On a Fly Drinking Out of His Cup 96.mp3

Take note that this is for a 32-second recording. A song or a five-minute podcast would be that much larger. I don’t think any of these rates would be small enough to tempt someone to download a file on their mobile. At least here in Africa there are many cheaper ways of getting mp3s through Bluetooth sharing and pirated CDs full of mp3s. In the developed world no one is going to want to download the New Testament on to their phone for example when they can get it faster and cheaper on their computer.