Limitations of MP3 recording ?

[g8ina]

I now have my setup all working nicely, but have noticed that if I use 320kbps MP3 recording, my iRiver cuts off at just over 16kHz, but if I use WAV recording, I appear to get up to 20kHz.

Is this common to other MP3/WAV recorders or just peculiar to my iRiver ??

Very happy with WAV files btw, I'm getting some great sounds recorded.

[RecoveringScot]

I now have my setup all working nicely, but have noticed that if I use 320kbps MP3 recording, my iRiver cuts off at just over 16kHz, but if I use WAV recording, I appear to get up to 20kHz.

Is this common to other MP3/WAV recorders or just peculiar to my iRiver ??

Very happy with WAV files btw, I'm getting some great sounds recorded.

I'm no expert, but as mp3 is a compression format, my guess is that what is lost in the saving of space will be the upper partials and higher frequencies, and the very lowest, that make a subtle, but not hugely different, quality to the overall sound. Older people will notice this less than younger people.

This page gives some info:

http://en.wikipedia.org/wiki/Audio_data_compression

Cheers,

[ermine]

Is this common to other MP3/WAV recorders or just peculiar to my iRiver ??


Record wav, then mp3 the item on your PC, and compare. You will observe something similar.

Perhaps more importantly, listen. Find a friendly and vocal local Starling. Record a section of his sound wav, and mp3. Then ask yourself if there is no difference. The loss of HF is perhaps the most benign of the side-effects of mp3.

http://www.suffolkbirds.co.uk/article/35/first-law-of-signal-processing

shows a sonogram comparison.

MP3 is engineered to work on tonal music allowing for our ears. You may analyze your birdsong on a computer. You may wish to listen to the song time-stretched to hear details we can't normally hear. There may be useful information in what you've thrown out.

For me the biggest hassle of bird recording and the highest expense is getting myself and my gear out there to record the bird. I don't see any wisdom in throwing out information I capture to save a few megabytes - and for me that is on small 1Gb minidiscs. Your Iriver has ten to twenty times that much - if I'd paid for that lot I'd sweat the asset and fill it up ;)

It's obviously your gear, time and hassle and your call, however, don't just assume MP3 sames you 80% hard disk space and just throws out 4kHz of bandwidth :) Some other viewpoints are

http://www.birdforum.net/showpost.php?p=546050&postcount=46


Cornell MD doctrine
We tested a popular early-entry portable field machine that utilized ATRAC 2 and found it to be unacceptable for natural sound recordings especially recordings that might be subjected to scientific analysis.

http://www.birds.cornell.edu/MacaulayLibrary/contribute/equipMd.html

and

The British Library
...However, the format uses a data reduction process to reduce digital storage space, which is designed to be transparent to human hearing. Whether this subtly damages recordings of wildlife is a controversial topic; however, you should be wary of using MD if your recordings might be used for scientific analysis later.

[g8ina]

Thanks Ermine....

I already recorded some side by side stuff using my son's MP3 machine, feeding the same mic signal into both and using WAV on mine and 320kbps MP3 on his, then the other way round.

It was most enlightening - even accounting for impedance mismatching etc by splitting the mic signals... !!

As you say, I have plenty of HDD space, so I'm gonna stick with WAV files.

Interesting links too, thanks. Links to my early efforts will follow as soon as I've got a good enough set to show off.