Hi I’m using audacity to measure the frequency of sound and I was wondering if anyone knows what units of frequency audacity records in?
Hz, or Cycles per Second. The power line in the US runs at 60Hz.
There are danger signals every time someone posts they are using Audacity for Scientific Purposes. Audacity is a sound performance editor not a WAV editor and it will occasionally take messy steps at variance with scientific accuracy in order to make the show sound better. The Show is our product.
We also get burned when people try to measure sound beyond hearing in both directions. That rarely works without adjustments or messy compromises. Another common problem is assuming a sound is only one frequency. That’s very rarely true in nature.
Describe what you’re doing. If you feel like it. We can sometimes save you a bunch of fruitless work.
Recording digital audio involves “sampling” the analogue waveform at regular intervals (thousands of times per second for normal audio).
The rate at which the audio is sampled (how many measurements are made per second) is called the “sample rate”.
The sample rate for CD quality audio is 44100 samples per second. This is normally written as “44100 Hz” or “44.1 kHz”
Audacity supports a very wide range of sample rates. There are presets for common sample rates (and a few less common rates).
Recording and playback are performed at the “project rate”. This is a global value for the current project. The project rate is set in the lower left corner of the main Audacity window.
Audacity also supports having audio with different sample rates in the same project. For example, you could import one file that has a sample rate of 44100 Hz and another that has a sample rate of 48000 Hz into the same project. On playback, the audio tracks will be resampled “on the fly” if necessary, so that all tracks play back at the correct speed (at the current “project rate”).
The sample rate must be at least double the highest audio frequency that you wish to use. (see here for an explanation of why that is: http://en.wikipedia.org/wiki/Nyquist_frequency)