Making a sound file as small as possible for web use.

I’ve got an mp3 file I’d like to put on a website. It’s a voice recording so I certainly don’t need high fidelity. I’m trying to use it as a click and play rather than as a download so I’m trying to keep it as small as possible. Right now I’ve got a file that plays for 7 minutes that is 3.25 megs and one that plays for 3:49 that is 2.59 megs. Are these files large given the length of the recordings? If they are and I
“rerecord them” what settings should I use? Also, is mp3 an efficient file form to use for the web or is .wav better?

  1. Change from stereo to mono
  2. Make it no more than 64kbps
  3. mp3 is FAR more efficient than WAV. There are other compression methods that are likely better than mp3, but I’d stick with mp3 for compatability.

Thanks Revtim, I just halved the file size. Is there a short version on the difference between changing Kbps and hz on sound quality and file size?

My pleasure.

As I understand it the bps is how much data per sample, and the hz is how frequently the samples are/were taken. I’ve never played with the frequency, only bps. I suppose lowering the frequency would also reduce the size and quality, but I can’t recommend anything since I’ve never tried it.

If you use the LAME MP3 Encoder you’ll be able to get better audio quality in the same filesize as other MP3 encoders. LAME also has a --voice encoding mode that will improve quality on voice files further.

As for samplerate vs. bitrate, bitrate (kbps) is the only thing that determines file size. Lower bitrate means lower quality, as less data is being retained. Lowering the samplerate simplifies the audio signal, as higher sound frequencies are thrown away. A side effect is that the remaining sound can be encoded with higher quality, as more space is available to devote to them. Resampling to 22.05Khz would be good at low bitrates, as there’s no real reason to keep higher frequencies. Going down to 16Khz may even be beneficial. Lower than that, the loss of high frequency audio sounds worse than the better reproduction of the low frequencies makes up for.