Cleaning up low quality speech for iPod FM x'mitter


I have thousands of low quality recordings of speech done on a cassette player in noisy environments over 20+ years. This has subsequently been converted to MP3 and I am now trying to play this from my iPod FM transmitter in my car. They sound absolutely horrible.

If anyone can guide me to clean these up a bit, I can apply the same effects to all the others and clean up all the other files. I am not expecting any kind of magic, as long as I can understand what is being said, that should be great.

Here is a example

Thanks in advance,

  • Manju

Do you still have the original cassettes? You will probably get better results by re-converting them at a lower volume level.

This has subsequently been converted to MP3

Given the technical quality of the MP3s (dreadful), that’s the step we need to address. How did you do that?


Do you still have the original cassettes?

I did not recorded this, I just inherited it. When I got this it was already in MP3 format.

How did you do that?

I did not do this, I got this from someone who originally recorded these and then converted them later, once computers became available. I have no idea what he used and this was done by a large number of people and I don’t think it is possible to find out what was done or used.

  • Manju

Not just the sound quality, but the technical quality of the MP3 files is pretty bad – if that one is a representation. The show has multiple different damages. I tried a several first-level patches and all I can do is make different damage – and, of course, I can make it worse.

It’s possible that the overly high volume level of the MP3 is causing damage in the FM transmitter magnifying the problem. Any chance you can burn the work to a Music CD and play that?

You ground your way into a tight hole. Audacity will cheerfully edit, process and change your work, but you can’t make another tiny, efficient MP3. You can make a very large MP3, or you can make WAV file and you can use that to make a Music CD with no further damage.

Open a show. Amplify > -3dB. Export WAV Microsoft 16-bit.
Burn the WAV file to a Music CD.


That mediafire download appears to require a password to download.

In the tiny fine print, they give you a way to get the file without the password.

Apparently, this changes depending on whether you have JavaScript and Pop-Ups running, but there is a way without the big flashing graphic.

I had script blocking activated on my browser so didn’t see the instructions.
I did manage to download it, but I don’t think anything can be done about the distortion.

The mains hum (50Hz) can be removed (by a notch filter), and the hiss noise can be reduced

The denoised, hum and hiss removed, sample sounds great. Thank you, I will work on the same lines.

One more issue I have is that the sample I posted earlier, seems to have a pretty low volume.
That is, on my car stereo, I need to set the volume to 26 to listen to the above file. But for example this one, which has been recorded more recently using a portable MP3 player directly, seems to have better quality and also higher volume. I need to set the volume to only 12-14.

But when I set the volume on the car stereo to 26, the noise also seems to become correspondingly louder, is it possible to fix this ?


  • Manju