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Checking if the speed of an audio file has been altered?
Sev_
post Nov 3 2014, 18:57
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Hello,

I am a freelance transcriber and was hoping someone might be able to help with my query. I have been receiving audio files recently to transcribe which I am convinced have all been speeded up by 10%, these are files of 1 to 1 interviews in mp3, wmp, format etc. The voices seem perceptibly higher in pitch, tempo of dialogue seems that bit faster etc.

I use Expressscribe software for managing file playback as I'm transcribing and once playback speed is lowered to 90% the interviews sound normal again and people don't sound like they've been sniffing a little Helium before conducting the interviews lol.

My question though is does anyone know of any way I can prove that somewhere along the way the original recording, which I do not have, has been speeded up either by the client of the company I freelance for, or by the company I freelance for, before it reaches the point where it's uploaded for myself or the other transcribers to claim?

The company pays according to number of audio minutes transcribed therefore speeding up interviews and subsequently reducing the sound file duration means either they're paying out less for doing the work or the client whose files are being transcribed are paying less to have the company deliver the work; either way I, as a transcriber, end up getting less so any help, pointers to any software anyone knows which could give me evidence they're talking faster than they should be, or even just terms I can Google (because I know nothing about technical audio stuff) would be hugely appreciated.

Hopefully someone can help,
Thanks
Sev.
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saratoga
post Nov 3 2014, 19:18
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You'll need the original recording to compare to, or at least to know the length of something in the recording. I'd suggest finding one where you have the source material, or at least have something recorded of known length.

By the way, if they wanted to speed up the file without changing pitch, that is quite easy to do.
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DVDdoug
post Nov 3 2014, 20:37
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If there is any line-frequency hum (i.e. 60Hz in North America, 50Hz in Europe), you might be able to filter-out everything else and do a spectrum analysis on the hum. But as saratoga says, it's fairly easy to change speed and pitch independently if they wanted to fool you.

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The company pays according to number of audio minutes transcribed therefore speeding up interviews and subsequently reducing the sound file duration means either they're paying out less for doing the work or the client whose files are being transcribed are paying less to have the company deliver the work;


You might want to re-consider your pricing policy. I can see how that policy would encourage speeding it up and taking out the gaps.... Is there anything in the contract that says they can't speed it up?

If you can keep up with it, faster playback will save you time too! There are two factors, how fast you can type and how fast you can listen... You might want to speed it up if can type faster! wink.gif You might also feel ripped-off if you charge by the word (or by the page, etc.) and you had a client that spoke slowly with lots of long pauses....

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Juha
post Nov 3 2014, 20:53
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Could it be samplerate issue (44.1 vs 48 = ~10%) ? IIRC, there were times when those things happened with certain software. Try by converting one of the mp3 or wma files to PCM (WAV) ... (Audacity can be used for this test).
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