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voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 4:12 am
by drspark61
I used Audacity (for the first time) to edit a radio talk show I host that was recorded at 150 kbps. After editing, I resaved as a 128 kbps MP3 using the LAME 3.97 encoder I placed in the Audacity folder.

The resulting file sounds sort of like we're all underwater, with a slight, garbled echo behind the voices. This is very pronounced when the file is played in Windows Media Play (v. 11), but less so when the file is imported into and played in Audacity.

Any suggestions?

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 4:21 pm
by steve
If possible, record as WAV, edit in Audacity and Export as WAV so that you have a high quality recording, then Export an MP3 version as the last step. If you need to do any further editing, or need to compress to a different kbps, you can do it from your WAV file. Every time that you decode / encode an MP3 file, the quality deteriorates.

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 5:08 pm
by Granpoh
How do you "record as WAV"?

Thanks

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 5:11 pm
by waxcylinder
Granpoh wrote:How do you "record as WAV"?

Thanks
You don't. To get music from a CD into Audacity you will need to rip it to WAV format first (several pieces of s/w can do this for you) - or you need to record it into Audacity. In both cases then will then have data in Audacity project format that Audacity can edit. Then you can export as WAV or a set of WAVs.

WC

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 5:20 pm
by Granpoh
waxcylinder wrote:
Granpoh wrote:How do you "record as WAV"?

Thanks
You don't. To get music from a CD into Audacity you will need to rip it to WAV format first (several pieces of s/w can do this for you) - or you need to record it into Audacity. In both cases then will then have data in Audacity project format that Audacity can edit. Then you can export as WAV or a set of WAVs.

WC
So if I connect a microphone to my computer to record voice samples, it'll only record in MP3 format and not in WAV?

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 5:46 pm
by waxcylinder
No, if you use Adacity to record it uses its own (very complex) file structures. Once you have finished recording and editing you can then export to WAV or MP3 (or Ogg - or FLAC in 1.3).

Wc

Re: voice recording saved as mp3 sounds garbly

Posted: Wed Jun 18, 2008 7:16 pm
by steve
Sorry folks, this confusion may be my fault.

When I said "If possible, record as WAV" I was referring to:
drspark61 wrote:I used Audacity (for the first time) to edit a radio talk show I host that was recorded at 150 kbps. After editing, I resaved as a 128 kbps MP3
What I meant was, that whenever possible, use uncompressed audio as the source material.

In the example given by drspark61, the source material was an MP3. This means that the source material (from the radio show) was already partly damaged (a consequence of being compressed as an mp3). This "damage" is then compounded by further losses when it is re-encoded for the final 128kbps mp3.

Audacity always works (internally) with uncompressed audio.

While the 150 kbps source file probably sounded good, (the losses/damage caused by mp3 compression was not noticeable), opening the mp3 in Audacity will convert the compressed mp3 back to Audacities uncompressed format, then when Exporting as MP3 it has to be compressed again.

This means that the original recording has been converted to mp3, back to uncompressed, back to mp3, and finally uncompressed when you play the file in your media player. All this format changing takes its toll on the audio.

So why does it sound worse in WMP 11 than in other players? Because WMP 11 enhances the high frequencies when it plays MP3 files. With a good quality MP3, this can make it sound brighter and clearer, but for mp3's that are more bubbly and jingly than they should be (such as audio that has been compressed and decompressed several times), the "enhancement" will enhance all the bad bits in the MP3 making it sound worse than it really is.

Re: voice recording saved as mp3 sounds garbly

Posted: Thu Jun 19, 2008 2:11 am
by drspark61
Thanks for the clear explanation. I thought something like that might be the cause of the problem, but I never realized the repeated compression/decompression would affect the audio that dramatically. I'll try to get the radio station to supply me with a WAV file next time.