newbie with bit rate question

Very new to this. I have a digital recording from a usb key which has a bit rate of 64kbps (file is 35.3Mb). When I open file in Audacity than export it (without editing), the same recording is now a bit rate of 256kbps and file size is 140Mb.

Please can anyone tell me how to keep the bit rate down so as to prevent ballooning file sizes (or point me in the right direction in the help file)?
Many thanks,

If you click on “options” button when saving as mp3 you can change the mp3 quality from 256Kbps to 64kbps if you wish …
mp3 quality demo 640px.gif
NB: if you save a 64Kbps mp3 as a 64kbps mp3 the result approximates to a 32Kbps mp3.
Save in a lossless format (like WAV or FLAC) to avoid generation loss that occurs when using lossy compression formats like mp3.

Thanks Trebor, very helpful. I was exporting to a .wav file when i got the file size increase.

Did you listen to it after you exported it? 32 should have sound pretty ratty (honky, bubbly) compared to the original file. MP3 gets its small files by throwing away sound quality. If you throw away too much, the show will start to sound damaged. Each MP3 export increases the damage, in your case by about double.

If you have simple editing or cutting, you’re far better off with one of the pure MP3 editors like MP3Splt. Those do not change the bitrate or the damage.