The sound recording

Digitizing the sound file

Once the recording is in hand, it is played into the line or microphone input of your sound card. I find it useful to send the output of the tape player into a graphic equalizer and then into the computers sound board. This allows me to filter out some of the low frequency noise (dogs barking , traffic etc.). Here is a diagram of how my computer is set up for sound recording and playback.

Using a sound digitizing program, such as SNDREC32.EXE (which comes with Windows95) or CoolEdit , create the sound file in 8 or 16 bit monaural format, (e.g.WAV format if you are using Windows) at a sample rate of at least 11,000 samples per second, but preferably at 22,000 or 44,000 samples per second. The sampling rates that you can use depends on the sound card that you have. The size of the sound file is proportional to the sampling rate..

The larger the sampling rate the higher the frequency that can be analyzed by a sonogram program.

Sample rate (Hz)

Highest frequency (Hz)







The relation is very obvious. If you are going to digitize birdsongs, which have frequencies up to 10,000 Hz, you should at least use a sampling rate of 20,000 Hz.

When you download sound files from the Internet , check to see what sampling rate is used. It is not unusual to see many digitized at 8,000 Hz, which makes them useless for sonogram analysis , unless they are recordings of owls, doves or crows etc.

I have a SoundBlaster 2.0 sound card on my older computer, and I use the DOS program BlasterMaster (available on Compuserve) because it allows me to use the cards highest available sampling rate of 15,000 samples/sec. I then use Gram23 to produce the sonograms.

On my newer machine I have a SoundBlaster 16, which allows me to record at a sampling rate of 44,000 samples per second and I use CoolEdit to digitize the sound and Gram23 to create the sonogram. I have also used the program Sona available as freeware at Avisoft. It is more sophisticated but harder to use.

If you have a Macintosh computer, Cornell Lab of Ornithology sells the Canary program that is a powerful but expensive sound analysis program

Windows 3.1,which I have installed on my older computer, has its own sound recording utility, which on my computer can only record at 12,000 samples/second. Windows 95 has a much better recording utility which can record up to 44,000 samples per second. Search around the Compuserve forums, read the manual for the sound card, and use whichever program that suits you.

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Revised April 30, 2004