At 3:55 PM -0700 8/29/05, Dan Dugan wrote:
>DAN DUGAN:
>> >Recording with 65dB SPL peaking at -5dBFS (and averaging around
>>>-15dBFS) brings the mic noise well above the floor of 16-bit
>>>recording. For the last several years I've recorded a wide variety of
>>>soundscapes with this level, which is what I get with 183s into a
>>>Sharp MD at MIC L 17. I found I had to drop my level 6dB (MIC L 14)
>>>to cover the crowded parts of the park. I can't recall any natural
>>>sounds except thunder I've had to turn down for, and some wind
>>>situations where the sound per se wasn't that loud but I wanted to
>>>keep the wind noise in the mics below clipping.
>
>ROB DANIELSON:
>> For relative ambient levels above the noise floor this should work
>>okay. Again, I was thinking you were going to study the
>>ambience/influences at a distance You may go down to just few bits
>>resolution if its a really quiet setting. Maybe these quiet settings
>>are no longer there to study.
>
>Of course quieter sounds are recorded with fewer bits, but that only
>matters when you intend to gain-up the recording -a lot-. I recorded
>water dripping in Golden Dome Cave at this level, and the mic hiss
>was the dominant sound (along with the drips). Saturday night it was
>very quiet in Muir Woods, and at locations away from a creek, the mic
>hiss was the noise floor, with plenty of room below that to the
>16-bit noise floor.
>
>If 65dB SPL is -15dBFS (VU averaging), 20dB SPL is -60dBFS. I rest my case=
.
It could be a difference in the objectives of our recordings. To
enjoy the sound elements that make up "ambience" in a quiet setting,
considerable amplification in post is unavoidable for me. I would
not elect to saturate the background at -45dB in the field if I could
help it. For example, if the background ambience peaks are -40dB
relative to my loudest sound and I set the record level for
saturating the loudest sound near 100%, the background peaks will
receive about 1% sound file saturation. If I recall correctly, 1%
saturation is resolved with about 5 of the 16 bits. When I take this
1% original and amplify it so that I can hear what is going on at a
distance, I'll get a lot more noise (primarily grunge and very
audible hiss about 2K) compared to an original field saturation of 6%
or even 3%.
Placed in practical context, I was recording all afternoon and all
night in an old growth forest two weeks ago. There were 2-4 sound
events per hour that reached 45 dB SPL. I choose to use a gain about
20dB above your peak voice ref of 65dB which, by pure chance,
rendered the peak events very near full saturation and gave me right
around 5% saturation for the background. Its my reasoning that even
if I get over-modulation a couple of seconds an hour, for the vast
majority of seconds, I'll have more data to resolve the background
ambience with. Rob D.
<snip>.
>
>-Dan Dugan
>
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
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