zoom h4n distortion

A

ad777

Member
Hey guys, i've been looking around for some help to this, but havent seen anything.

i just recorded a bunch of narration for a short film im doing. i used my brand new zoom h4n. i was recording in stereo mode 48k mp3. it was battery powered with a me66 hooked up. the m66 had its own battery and was not phantom powered. we were in a sound booth. i had the actor very close miced and then wrapped in a thick quilt. the levels were around 60 and hitting -12db. i monitored the audio through headphones the whole time. i admit they are crappy headphones, but i could still hear everything and it sounded great.

i just opened up my files and they are full of distortion. they sound like crap. it sounds tinny and very compressed. the only thing i can think is that my battery was going out as i was recording. by the end of the session i had the low battery sign blinking. i think when i started there was one bar left. i havent seen any other complaints about low battery ruining audio though.

im not sure, but i think its either that something is wrong with my zoom, it gets awefull distortion when the battery is low for some reason, mp3 format is compressing the crap out of it (dosent make any sense), or my mic placement somehow caused distortion (again, i was listening the whole time and never heard anything close.

i had recorded sync sound on a shoot a few days before and that stuff sounds pretty good, its hard to tell though because its only coughing and walking through the woods. there was no dialoug recorded, so its hard to make a fair comparison.

any ideas on why my audio is distorted? i would really like to figure out what the problem is before i try to record the narration again. its very emotional narration and im dreading having to tell my actor that we need to do it all over again.

thanks
 
"distortion" is a fairly loose term that could describe a number of issues. Can you post a sample?

And for the future, there's no reason to pretty much EVER record in mp3. Always record to .wav files
 
Well the first thing I think of is you were recording to MP3????? Why would you do that? It might well sound "it sounds tinny and very compressed" because it is. You won't hear this in the headphones while recording because your listening to what is coming in not what is getting squashed down to the card. MP3 can sound OK if your recording at a high enough bit rate but you don't say. If I had to guess I would bet you were at a low bit rate.
For future reference you NEVER want to record tom a compressed format unless you have no choice. In your case you should have been recording WAV files at 48/24 or 48/16.
 
i am not saying its not the mp3 causing the distortion, but as i said i was recording stuff earlier that week with all the same settings and it sounds ok as far as i can tell. i was recording to mp3 to save card space. i now realize i would still have plenty of card space with WAV. it was my understanding that mp3 isnt overly compressed. what i mean by that is you normally dont get noticable distortion. music is often mp3 format and sounds great, so why would my stuff sound like someone did a really bad noise filter on it?

as for posting some samples. i would like to, but i dont know how. i assume i would have to upload them to another site and post the link. anyone know of an easy site to do this?
 
ad777 said:
it was my understanding that mp3 isnt overly compressed. what i mean by that is you normally dont get noticable distortion. music is often mp3 format and sounds great, so why would my stuff sound like someone did a really bad noise filter on it??
Click to expand...

MP3 is drastically compressed. 3:30 of stereo audio at 16-bit/44.1kHz WAV is about 36MB. Converted to an MP3 at 192kbps, which is a really high-quality MP3, it is 5MB. That's a lot of data thrown out.

MP3 is also an end-user or distribution format, not an acquisition format. Yeah, music MP3s that you download from iTunes (which may be Apple's "lossless" AAC, but still highly data-compressed) may sound fine to you, but try converting them back up to a full-rez AIFF or WAV and you'll start to hear artifacts.

To edit your MP3-recorded audio, you'll have to convert it to uncompressed WAV or AIFF. So all that information that was removed to shrink the file size has to be replaced, and the computer isn't really very good at guessing what used to be there. So you'll hear artifacts. And depending on your MP3 settings, you'll hear some pretty nasty stuff.
 
What he said. Also MP3 can be created at a lot of bit rates and low ones sound progressively bad. You didn't say what bit rate your MP3's were at so? The other thing with compressed formats is that they can react strangely to some sounds. The classic case is recording a car horn go by or a siren. The compressor can freak out and produce all kinds of aliasing effects that just sound weird. It was one of the drawbacks of MiniDisk (it used a different codec but similar to MP3). The other think is the quality of the compressor. Most computers these days will compress to MP3 at faster than real time but that wasn't the case a few years back and the "computer" in a small portable recorder is not nearly as fast and has hardly any memory. The result is that they do a very quick and dirty on the fly compression to be able to keep up with live recording. Those songs that "sound great" are probably pop songs and have been compressed (dynamically) within an inch of their life. The mastering of most pop songs is very close to what you would do to make something very MP3 friendly. The real world recordings you are doing are not very MP3 friendly.

But it is possible that the "distortion" your noticing doesn't have anything to do with MP3. It could be a completely different problem. You should still not record MP3 in the future. As C2V mentioned MP3 is a delivery format not an acquisition format.
 
Thanks for the follow up. It really ups the usefulness of the thread to others when there is some resolution posted.
 
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