How to reduce audio file size from 10mb to 2mb

I conduct an online class using Skype and record each session, about 30minutes. After the class, I need to send/upload the audio file, about 10-15mb, to the participant. I need help to reduce the audio file to 2mb or smaller for quick transmission.

Can anyone help?

I have windows 7 professional, Audacity v 2.1.2

CD quality stereo WAV files are about 10 MB per minute.
Mono CD quality WAV files are about 5 MB per minute.
Telephone quality (11 kHz sample rate 8-bit) WAV files are about 0.6 MB (600 kB) per minute/
CD quality stereo MP3 files are about 1.5 MB per minute.
CD quality mono MP4 files are about 0.6 MB (600 kB) per minute.
Telephone quality MP3 files are about 0.25 MB (250 kB) per minute.

There are also less well known codecs such as Speex and Opus that can produce telephone quality mono audio files as small as 60 kB per minute, but Windows / Mac users are unlikely to be able to play them without installing additional codecs or using a better media player than these operating systems have by default.

Probably your best option would be to export from Audacity as 64 kbps CBR MP3, upload the file to a file sharing site such as “dropbox”, and email a link to the on-line file to those that need access to the file.

Thx. Very informative.

And one other note, all those values and settings only work well if the client only wants to listen to the work. If they intend to edit, apply effects or do any other production to the voice, then the higher quality (and larger) sound files are very highly recommended. Each time you make an MP3 from an MP3, for example, the quality degenerates. Never use MP3 in the middle of show production. Use WAV until the final delivery, and even after if you can.