Raimund wrote:
>--- In Rob Danielson <>
>wrote:
>>Part of our difference in whether mic sensitivity is a factor could
>>be our usual recording environments/goals. When isolating a bird
>call
>>with a mkh-60 or parabola, the noise introduced by sensitivity is
>>usually not audible in the sound file. The saturation of the
>>sustained body of the call might be 20-40% with percussive peaks in
>>the 60%-100% range. To contrast, in the middle of the night in a
>>rural setting, with an MP-2 cranked max and mkh-20's (10dB[A]
>noise),
>>the noise floor of the forest will produce 6% sound file saturation
>>with distant effects reaching ~12%. The later file has to be
>boosted
>>a great deal digitially to be heard upon playback and is a demanding
>>test of noise, from any source, including bit depth and resolution.
>
>Hi Rob,
>
>I agree, that such quiet ambient recording situations are much more
>demanding than recordings of relatively loud calling animals at
>close distances. However, I believe, that it does not make much
>sense to amplify extremely soft sounds artificially for playback.
>You should listen to these recordings also in a quiet environment
>(e.g. using headphones) at low sound levels with the playback volume
>adjusted not much louder than at the original recording site. You
>could improve the subjective quality of a recording, if you placed
>the microphone as close as possible to one or two foreground sound
>sources (e.g. a calling owl or something else) in order to increase
>the peak sound level (and the dynamic range). This would also make
>the situation more interesting to the listener. Another trick is to
>fade in noisy recording slowly. This would allow our ears getting
>used to the noise.
>
>The logarithmic sound level scale is based on the dynamic range of
>our human auditory system. 0 dB corresponds to the lowest sounds
>that we are able to perceive. A microphone noise floor of 10 or 5 dB
>would be very close to our hearing threshold. However, when
>considering these few remaining dB's, mother nature still seems to
>have the more advanced know how in designing low-noise
>omnidirectional 'microphones' than any other human microphone
>manufacturer ;-).
>
>As Walt pointed out recently, the absolute sound levels in natural
>environments are usually very low. Imagine, you recorded a soft
>sound, lets say with a peak amplitude of 40 dB by using a microphone
>having a self noise level of 10 dB. When you then playback that
>recording at a higher volume in your living room (e.g. 20 dB louder
>than at the recording site), the original microphone noise of 10 dB
>would be reproduced at 30 dB (10 + 20) and the peak sound level at
>60 dB (40 +20). The amplified microphone noise of 30 dB can then be
>very annoying. However, if the original sound level at the recording
>site were louder (say 60 dB), and you set the playback volume also
>to 60 dB (20 dB less gain compared to the first example), so that
>you have the same sound level in your living room as at the original
>recording site, the microphone noise would be reproduced at 10 dB
>only. That soft noise would be nearly inaudible. Therefore, the
>subjective quality of a field recording would be better if the
>original absolute sound level at the microphone was higher.
>
>This seems to be the case in Evert's recordings he made with the
>SoundMan microphones. The ambient sound level in a train is usually
>higher than in a quiet natural environment. Additionally, the broad
>noise spectrum in a train will mask out the microphone noise (by
>psycho-acoustic effects).
>
>
>MIC DIY mics:
>>The MP-2 spec
>>says that the input noise is -128 dBV so that the self noise of the
>>mic is 12 dB above the noise of the channel. This isn't as big a
>>difference as I expected but if you take a noise signal you won't
>>hear much difference at all between it and it added to a noise
>>source 12 dB lower so that it is safe to say that the mic self
>>noise, low as it is, will mask the noise of the MP-2.
>
>It should be noted, that two independent noise sources (the mic
>noise and the pre-amp noise) will add geometrically. This means,
>that the sound levels of the two noise components (expressed
>linearly in Pa) will not simply add. Instead, the resulting sound
>level of the two noise components will be less than the sum of the
>two. For those who are familiar with this kind of math - it is the
>root mean square:
>c =3D sqrt (sqr(a) + sqr(b)) where a and b are the two noise
>components and c is the resulting noise level.
>
>When comparing mic noise and pre-amp noise, one should also
>consider, that the condenser microphones we are talking about
>already include some kind of amplifiers. A classic condenser
>microphone requires at least one FET transistor or a tube to convert
>the high impedance of the condenser element to the low impedance of
>the output connector. The Sennheiser MKH series microphones use
>instead as special HF circuit to replace the noisier FET transistors
>by normal bipolar transistors. Actually, the condenser element
>modulates the frequency of an oscillator running at about 2 MHz (if
>I remember correctly), which is demodulated subsequently (similar to
>a FM radio receiver). All the transistors in that circuit have
>similar properties to those employed in a pre-amplifier. Therefore,
>the transistors of the microphone represent the very first stage in
>a chain of several amplifiers. Generally, the total noise floor of a
>compound amplifier is mainly determined by it's first stage (the
>microphone in this case).
>
>>Sensitivity will not play a role with the very good mic
>>pres, but the pres most field recordists use don't fall into this
>>category. MD manufacturer's, for example, don't publish noise specs
>>on the mic preamps of their consumer recorders. The mic pres in the
>>TASCAM DAP1's I frequently borrow are not as quiet as the MP-2 and
>>they do start to introduce noise when cranked with mkh-20's to my
>>ears. I've not seen useful noise specs for the TASCAM either.
>
>Yes, there are differences between the various recording gear.
>Especially in small portable consumer recorders, the manufactures do
>not use the best available electronic parts. There is a tradeoff
>between noise performance, supply current and price in the available
>electronic parts.
>
>Regards,
>Raimund
>
Hi Raimund--
Thanks for taking the time to bring the discussion back to the places
and circumstance we occupy. Fewer and fewer listening opportunities,
even with headphones. For a recent surround sound installation
comparing listening environments day and night urban and rural, I
used a free standing planetarium, turned off the HVAC and found the
city penetrating the walls at 30 dB. The high levels demand
recordings that "pop," yet enlightenment requires effort-- records
that lay back and invite. The experiment suggested to me that
current frustrations, the "filtering" and withdrawals from
communications within mechanical environs, are still first reactions
to-- a 150 years of inherited and personal exposure? People who
heard the installation reported they were prompted to walk to work
again and talked positively about hearing collectively what is there
all the time. The incredible listening talents we possess as animals
are still in tact waiting for old or new roles to surface. I sense
that quite a few people are running run around with pretty decent
sound recorders and dedication. My grandfather left me a box of 16mm
black and white films from 1927-1933 and I ended up with an MFA in
film. Among the junk the next few generations will be rummaging
through will be boxes of marked and unmarked CD-R's and minidiscs.
As a film and video maker, I know well close micing, layering and
mixing in the retreat of headphones. What I have learned through my
buttocks, is hard to unlearn, but I'd like to bring my mediated
experiences closer to place, back to particulars of selected
experiences. I am not a purist, I will layer and fabricate to no
end if it takes me back more knowingly to the original spot, but,
like most, I prefer being in the field. I didn't know where to seek
out good advice as I became interested in field recording and have
only recently come to this list which has been a tremendous help. Its
obvious to me now that low noise, for me, translates into to less of
the most tiring aspects of the work. But should one trade in the 10
years of learning to equalize? Tell me; my guess would be self-noise.
Rob D.
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