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Topic: Distortion in audio from Zoom H2 to Audacity

I am using a Zoom H2 to record audio for my slide shows. I record as MP3 or Wav and the results are the same when edited in Audacity played back on Widows Media Player. I set my recorder in one of the limit modes so gain is controlled by the recorder. I import into Audacity, edit and then save as MP3 file.
The link below is a sample of the sound. I am not talking about the clicking and popping when the speaker says "P" or "T". Any advice would be appreciated.









http://www.vhphoto.net/distortion/DennisFinal.mp3

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Re: Distortion in audio from Zoom H2 to Audacity

Can you export as a WAV from Audacity and post that as well?  It's hard to know what's being added by the compression and what was already there without hearing the difference in the two files.

joe

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Re: Distortion in audio from Zoom H2 to Audacity

Joe,

I capture the audio in MP3 format and then edit in Audacity and export out of Audacity as MP3. I have captured audio in WAV format, imported into Audacity, made my edits and then exported as an MP3. The problem did not go away.

Jeff

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Re: Distortion in audio from Zoom H2 to Audacity

Jeff.

What settings do you have your Audacity exporting to MP3 set at?

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Re: Distortion in audio from Zoom H2 to Audacity

oldsurfer wrote:

Jeff.
What settings do you have your Audacity exporting to MP3 set at?

Exactly what I was thinking.

It could be that your Audacity MP3 setting is over compressing the audio, especially if you're compressing an original MP3 file.

Try this as a test ...

Capture as WAV, then export as a WAV from Audacity.  Does the resulting audio file sound better?

If so, then the problem is most likely the MP3 export from Audacity.  We can help troubleshoot your settings if that is indeed the problem.

-joe

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Re: Distortion in audio from Zoom H2 to Audacity

Joe,

Thanks for your input. I tried the WAV recording and then export in MP3. Problem still there. I am looking for answers over at the Audacity forum. So far no luck.

Jeff

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Re: Distortion in audio from Zoom H2 to Audacity

Jeff,

From your description it sounds like the original Zoom H2 audio is just fine. Is that correct?

Assuming yes, it seems the problem occurs in Audacity for some reason. But I'm not completely sure because it doesn't seem like you followed one bit of Joe's advice: try exporting as WAV. (I realize you want the final product as MP3, but this is for testing purposes.) Does that exported WAV have the problems also? If so, then there's clearly something not working quite right when in Audacity. On the other hand if the exported WAV is fine, then the problem is with the MP3 export process specifically.

If the problem really truly is with the MP3 export, then at least there's a workaround: export as WAV and then convert to MP3 using iTunes.

If the problem is noticed with the exported WAV, then that's much trickier. I have no idea what the problem would be—except to test out another audio editing program and see if the same problems pop up again (or not).

BTW, the Zoom H2 is much worse at capturing good audio using MP3. It does a much better when you capture at WAV. (This has to do with the relatively weak preamps, and the various demands of recording/compressing at the same time, which the Zoom H2 does not handle well.)

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Re: Distortion in audio from Zoom H2 to Audacity

The problem could be with the limiting applied by the H2. Ideally, you want as strong a signal as possible without crossing the clipping threshold. And that's why some people have a tendency to automatically apply limiting and compression to their recordings.

While these portable recorders do an amazing job for the money, they are not built with top quality components and processors. Some audio people might describe your recording as "crunchy" or "hot," and that is sometimes a result of too much limiting or poor quality limiting. You would probably be better off recording naked, with no processing. You can always add limiting and compression to even out your sound in Audacity.

That means you might have to set the levels yourself, but that's usually not a problem with interviews. I have an H4, and it offers a choice between compression and limiting, but it also has an option for "auto gain," or AGC. (I'm pretty positive that the H2 offers the same options.) Instead of continually monitoring the input and adjusting the gain to optimize the levels, it scans the level while in record-ready mode and sets a static value based on that. This eliminates the unpleasant "pumping" that can result from constantly-shifting gains, especially overshoot from a brief loud sound. Your levels may be a little lower than desirable, but you can really clean things up in post processing. Normalize your recording. If you have some noise or hiss, Audacity has a pretty good noise reduction plug-in. Using the built in compression or limiting in the H4 and H2 can really amplify any background noise, as it is, and the constantly changing gain can make the noise more difficult to remove. If you set your own levels or use AGC, any noise will remain at the same level and is easier to reduce or remove.

If the volume of your subject is a little erratic (gets louder and softer), it's better to squeeze your signal a bit with compression or limiting in Audacity because you have control over the amount applied.

So, anyway, try making a recording in the WAV mode and setting your own levels, or use AGC. Then do any other processing in Audacity, or whatever audio editor you might use. Avoid recording in MP3, then exporting in MP3 -- it's akin to shooting in JPEG, then re-saving in JPEG after editing -- every time you recompress, you lose more information and more quality.

Also, if you are creating audio files to import into Soundslides, I would highly recommend downloading the LAME component for Soundslides. Export your audio from Audacity as a WAVE or AIFF file so you always have a full quality version. Then, when you import into Soundslides with the LAME component, it automatically creates a good quality MP3 version at an appropriate bit rate.

(Honestly, your slightly crunchy recording isn't nearly as bad as some of the jingly jangly, artifact-ridden audio that I've heard as a result of low bit rates. Low bit rates save band width and storage space, but they sound so bad that they devalue and interfere with the telling of some potentially good stories.)

Hope that helps. Write back and let us know.

9 (edited by luvecor 2012-07-04 06:42:05)

Re: Distortion in audio from Zoom H2 to Audacity

@ whynotsb
thanx for your detailed answer. i dunno about jkubacz but i found your explanation very useful for me