Cleaning telephone audio I have telephone audio at 16kHz and I am trying to use it with a speech transcription engine that converts spoken letters to text. However, the engine has some difficulty transcribing certain letters such as "p" and "t" due to the low quality of the audio.

This is being used in a real time application so although I would like the user to speak clearly, into the microphone in a quiet environment, this won't often be the case. The transcription engine has its own background noise removal however it isn't trained on telephone audio.

In light of my ignorance, I was hoping someone could make some suggestions on how to artificially "improve" the quality of the audio. I know this is vague but I would like to try and make the speech in the audio more discernable and experiment with the transcription engine. 

Can I try and remove the static sound?
Is it possible to "amplify signals" that are unique to a certain letter?

Thanks
The transcription engine has its own background noise removal however it isn't trained on telephone audio.


There are many engines which are trained on bad quality audio and which perform just right. 

It is pretty hopeless to repair the quality when it is already lost, it is better to find an accurate engine.