How to remove annoying monotone sound?

[solarplexus]

hi everyone!

I recorded an interview of my grandmother with a dictaphone. I digitalised it but on the original tape you already hear on the background quite loud an annoying background sound. A sort of monotone buzzing. Because of this the voice of my grandmother sometimes is tOo silent.
How can I remove this sound?
Noise removal doesn't work: it changes the buzz into a sort of echoing buzz
FFT-Filter might work? If it does, can somebody explain me how it works? I don't understand it...

Thanks so much!!

greets, Jan (Belgium)

[kozikowski]

<<<Because of this the voice of my grandmother sometimes is tOo silent.>>>

Noise removal only works when you don't need it to. There was another posting on the board of someone who had voice that was being swamped with Something Else. It almost doesn't matter what the Something Else is, once that happens, most noise removal tools are helpless. The voice has got to stay louder than the junk.

The other thing that kills you is if the noise is broad band like a buzz instead of a hum. By the time the tools take it all out, there's no voice left, either.

Can you post some of it somewhere so I can get to it? Try to include a place when she stops talking for a second. That's pretty important.

Oh, FFT Filters are just regular filters that are executed with Fast Fourier Transform instead of any other technique. They're not going to help you a bit--but let me listen to the track before you fall on your sword.

Koz

[kozikowski]

I can't put dollars-American on this yet, but did you play the actual DictaPhone tape back on an actual DictaPhone? The same DictaPhone? As near as I can tell, those machines had a control or information track recorded in addition to the actual performance.

If you try to play the tape back on an ordinary tape machine, you'll get the information control track overlaid with the voice. It should sound terrible.

Koz

[solarplexus]

did you play the actual DictaPhone tape back on an actual DictaPhone? The same DictaPhone?

That's what I did yes. The sound is already on the original tape.

I put a short track of it on this link: http://www.theban.be/gm.mp3
Around the 23th second there is some silence (that is, a part where my grandmother doesn't speak but the buzz-sound is heard)

Thank you so much for your help!!!

greets

jan

[kozikowski]

You got a good one there.

I posted a corrected clip:

http://www.kozco.com/audacity/gm_corrected.wav

That's two passes through the Cool Edit noise correction filter (not Audacity). I think the result is terrible and I know why. You picked a noise that has a lot of the same characteristics as the human voice. It's really rough to separate them.

I want to try this once again with a little change. You gave me an MP3 clip of the voice. MPEG1, Layer 3 (its real name) is a destructive compressor. It damages everything it touches. So the clip you gave me is 10:1 compressed and damaged compared to the one you have. I want the real, undamaged thing. I'm expecting a 3M to 7M clip, not a 700K clip.

You can save some data space by converting to mono and deleting the right channel which is silent in the clip I have. In audacity it's "Split Stereo Track" from the pull-down menu on the left. Send "Export as WAV...".

Koz

[solarplexus]

Indeed it sounds strange the correction. The background sound on the original tape is always the same one though. Unfortunately.

I split the track as you said and exported it as wav. It is now 7.4MB and I put it here:

http://www.theban.be/gm2.wav

I already thank you so much for your help and effort!

Jan

[kozikowski]

I'm hoping that "Space Alien" sound will go away when I get a better clip. The noise removal tools and the MP3 compression tools work on the same Fast Fourier Transform technology and they can fight each other if used in the wrong order. The MP3 compression is supposed to happen as the last thing before delivery, not a production step in the middle.

I'll get to this in a minute.

You know you can do the same thing I'm doing with the Audacity noise reduction tools, right? find a segment with no voice and select it. I forget exactly how the tool works, but after you select and capture the noise profile, you apply the correction. It may not help. Like I said, given the noise you have, and the amount of it, the chances of pulling a nice show out of this is almost zero.

By the way, you're busted. The room was really that noisy during the recording wasn't it? Was that a fan or an air conditioner?

Koz

[solarplexus]

Belgian climate not really requires fans or air conditionning

You know I think the sound you hear, is the sound that the dictaphone made when it was on and it recorded it at the same time. Could this be?
In an interview of my grandfather I used an external microphone, and i don't have the problem there... And it was in the same room...

jan

[kozikowski]

I think I'm going to give up. The new clip was very slightly easier to use, but I couldn't get a better final show. Very slightly less space alien sound. I did an analysis of the Room Tone (buzzy sound) and it has the same personality as someone talking. I can make use of the fact that the pitch and volume do not change, but I think we will never get rid of it completely and either the room tone or the voices will always sound a little like they're in a barrel.

Sorry.

Koz

[solarplexus]

That's a pitty. Thanks a lot for your effort anyway.

one question though? You think some professional company could 'clean' this recording? Or do they use the same techniques and would the result be the same barrel-sound?

Unfortunatly my grandmother past away so I can't do the interview again. Still I would like to keep it for the future.


regards

Jan