I’ve installed Audacity 2.0.5 and the LAME plugin on a 64-bit Win7 laptop. I can’t seem to export MP3s at 32,000 Hz; even when I choose that rate from the drop-down menu in the lower left, when I attempt to Export it, it always saves it at 128K samples per second. Am I just misunderstanding how this works, or is there something I’ve missed? I’d appreciate any help from those who might have ideas or suggestions. Thanks for your time.
Strictly, LAME is a library.
The sample rate (project rate) is bottom left. This does not affect the file size of exported MP3’s (though it does affect file size of exported WAV files).
So generally you want to use 44100 Hz project rate for maximum compatibility with MP3 player applications.
Bit rate (measured in kbps) affects MP3 file size and quality directly. It is chosen by clicking the “Options…” button bottom right of the export window (where you type the file name).
If you want the very low quality of 32 kbps, you may be better to not use 44100 Hz project rate. You probably won’t get higher frequencies than about 5000 Hz with 32 kbps, so you may be better to use 22050 Hz or 11025 Hz project rate and not waste the few bits you have on higher sample rates.
You might be confusing the sample rate (Hz or kHz) with bit rate (kbps)… What are you really trying to accomplish?
The sample rate is related to the highest audio frequency you can record/store, and also related to file size for uncompressed files.
The bit rate is related to file size. It’s the number of bits used to store 1 second of audio. It’s normally used with compressed formats, although you can calculate the bit rate for uncompressed files. (There are 8 bits in a byte.)
(Audio frequency, related to pitch, is also expressed in Hz or kHz.)
Based on subsequent reading, I believe you’re correct; I had confused them. I’m merely trying to reduce the file size, and willing to reduce audio quality to get it. Since the highest audio frequency I need is not that high – adult male spoken voice, typically well below 1 kHz – reducing the sample rate seems like a simple way to get it, and I think I’ve been doing that right. Perhaps I can play with the bit rate more to get the file size still smaller.
Thank you both for your help.
If the objective is file size reduction in MP3, only reducing the bit rate will do that. The sample rate does not affect MP3 export file size.
Reducing the sample rate may be desirable with very low bit rates because it is likely to lessen the quality loss compared to higher sample rates with very low bit rates (for the reason above).