How to amplify after noise removal w/out adding noise

[Roxanne1149]

The detective insists it is not his recorder, but the recordings I have received from him lately, even when not recorded in large, open places like jail bathrooms, sound like this recording. Could it be the way he downloads/saves the audio files?

Thanks for trying to help, Trebor. I was really hopeful.

[Trebor]

The detective insists it is not his recorder, but the recordings I have received from him lately, even when not recorded in large, open places like jail bathrooms, sound like this recording. Could it be the way he downloads/saves the audio files?

Yes, an echo effect can be created by accident when using an audio editor like Audacity, (search this forum for “corridor”).

I’m confident the recording device did not create the whistley R2-D2 compression artifacts, IMO they have been added by using extreme compression settings in an audio editor (like Audacity) to minimize the size of the audio file, e.g. to send the smallest (MP3?) file possible by email, but which has mutilated the recording in the process.

BTW I've heard the recording a several times and think I can make out part of it, however to me some of the voices sound like they are speaking with my accent (Scottish) which is a symptom of pareidolia, i.e. my brain may be making this up …

Aint so crazy about.wav

(614.65 KiB) Downloaded 65 times

01-02 : “ Huh ? ”
02-04: Corey “ Aint so crazy about me being in America "
04-05: Scot : “ well I‘ll tell you ”.
05-06: US Lawyer (interrupts Scot) “ it's not about you ”.
06-07: US Lawyer “ Did you sign it ? ” .
08 : Scot “ Hard Luck ” (sarcastic).
09-10: US Lawyer “ again Did you sign it ? ”.
11: Cockney Lawyer "own up".
12: US Lawyer “ Correct ”.
12-14: US Lawyer “ they haven't told you did ? ”.
Cockney Lawyer " No "
13-15: US Lawyer “ OK gotcha ”.
15: US Lawyer “ Corey " (interrupted by Cockney geezer)
15-17: Cockney Lawyer “ the judge will tell you right now ”.

[steve]

Could it be the way he downloads/saves the audio files?

That could be at least part of the problem.
Much of the damage is due to data compression (as Trebor said).
If audio is compressed to a lossy format (such as MP3), some of the sound quality is lost. There is a trade-off with lossy compression of sound quality vs. file size. The loss of sound quality is permanent and unrecoverable. If a file that has been encoded in a lossy format is compressed again (transcoded) to a lossy format (for example, changing a WMA file to MP3), there is further sound quality loss. The sound quality gets worse each time it is encoded.

Ideally the file that is sent to you should be the original recording in whatever format it has been recorded in.

[Trebor]

It sounds like it was recorded via an echoey tube, like an air-vent or drain-pipe.

If the echo isn't an artifact from incorrect use of an audio editor here is a possible explanation ... http://www.postgazette.com/pg/07179/797810-85.stm

[Roxanne1149]

Thanks Trebor and Steve. I will be relieved and feeling kind of stupid if it is just a matter of the file being compressed for email too many times. That did not occur to me since I have no other problems with other clients who email files to me, but I believe this file had been put on a disk, given to another party, then the file was emailed to me from the disk and third party. I usually receive my files from sendthisfile.com and not by email and they are normally coming right off the interviewer's computer after they download the recording, except for this time. I hope the compression is indeed the issue. Thank you for educating me!

[Trebor]

I have no other problems with other clients who email files to me

Sending an audio file by Email per se does not introduce the compression artifacts.

The file size restriction on email attachments, (5Mb - 25Mb depending on email provider), may have obliged the sender to compress a large audio file, (using something like Audacity), which in this case they have overdone, mangling it in the process.

I believe this file had been put on a disk, given to another party, then the file was emailed to me from the disk and third party

The reverberating echo and whistley compression artifacts could have been added by the person who created the disk, or the person who copied the disk and emailed you the file.

If the “other party” tried to copy the audio from the disk using the record “what-U-hear” method *, (rather than just copying the audio file from disk to computer without playing it), they could introduce the corridor/hall reverberating echo effect by accidentally recording the output of the audio editor whilst playing and recording the disk ...

Note: Do not enable "software playthrough" when recording computer playback, because this creates a series of echoes.

http://audacityteam.org/help/faq?s=reco ... =streaming


[* playing the audio on the disk using a media player on the computer then recording what you can hear on the computer speakers/headphones using an audio editor like Audacity]
http://audacityteam.org/help/faq?s=reco ... =streaming

[Roxanne1149]

I received the audio files again from the source after he downloaded them from his digital recorder to his computer, through sendthisfile.com. It still sounds just as bad. I am going to go pick up a disk now and see if that is any clearer. Do I have any options to fix if it's just as bad on the disk?

[Trebor]

I received the audio files again from the source after he downloaded them from his digital recorder to his computer, through sendthisfile.com. It still sounds just as bad. I am going to go pick up a disk now and see if that is any clearer.

The person with digital recorder will be tempted to edit the file so they only send you the relevant part recording using an audio editor like Audacity. Ask them not to use an audio editor, ask them to send a copy of the whole file on the recorder which contains the relevant conversation, i.e. Connect the digital recorder to the computer and upload the audio file directly from the recorder to the sendthisfile.com

If they use some sort of audio editor (like Audacity) in the transfer of the data from digital recorder to their computer to your computer, the same reverberating echo and compression artifacts could be added again.

If the person gives you an exact copy of the file on the recorder that’s the best quality you are going to get.

An exact unedited copy of the file on the recorder may be very large: hours / 100s of Mb, with the relevant portion only a few minutes / 10s of Mb, but it's worth the excessive download time to get a comprehensible recording. (It’s still quicker than it would take to teach your source how to use an audio editor correctly).

Do I have any options to fix if it's just as bad on the disk?

The whistley R2-D2 compression artifacts are incurable. There are de-reverb tools which reduce reverberation, but don't bother as they aren't going to help in a severe cases like yours, (and they can be horrifically expensive).