On 03/16/2014 09:50 PM, Lorenzo Sutton wrote:
i once talked to a bat researcher (no joke) who had a simple mod to a
røde nt5 that would allow it to work reasonably well up to 30k.
earthworks make special versions of their excellent microphones which
are linear up to 50khz, for those who need it (or think they need it).
in fact, most if not all microphones can do this but for additional
filters added by the manufacturers to increase robustness in the
presence of HF electromagnetic noise. the question is how linear they
are up there, and whether the pickup pattern is still useful. all but
the smallest capsules can be expected to become highly directional at
HF. something like a DPA 4060 or a SH MKE-1 might be good experimental
capsules for ultrasonics.
> Likewise can anyone point out any commercially available speaker used in
most tweeters are easily capable of 30khz, and there are no major
engineering obstacles to 50khz on-axis.
the big issue is excessive beaming, both on the recording and playback
side of things.
> If the audio produced is made for fruition of humans it makes absolutely
i'd tend to agree with that statement, but there are very valid reasons
to do it:
* not all recordings are meant for humans to hear - if you are measuring
something, you might appreciate results outside of human sensation.
* not all recordings are meant to be heard in its original frequency
range - talk to any bat enthusiast. seriously, what those guys do makes
you itch to try 192khz and a microphone that is open "from dc to
daylight", as the saying goes.
* sometimes, preservation of information is extremely important. for
instance, there are valid reasons to digitize old analog tapes at
ridiculous rates (say, 384 kHz): doing so lets you record traces of the
HF bias, which might help in eliminating wow and flutter artefacts more
precisely than tracking the 50 or 60hz power grid hum.
or there's a colleague from italy, david monacchi, who records sound
scapes in soon-to-be-destroyed natural habitats - why would you limit
yourself to 10 octaves if you can get 11, before the bulldozers arrive?
(i once heard him lecture on one of his works, and indeed he was using
sonograms to identify certain species of animals, many of which are
capable of uttering ultrasonics.)
there is still ongoing debate about indirect audibility of high
frequency content via transients - i'm not too convinced, but i can
understand any colleague who would rather record too much today and then
downsample, as opposed to finding you won't be able to fully exploit
future distribution formats with your legacy material. if i'm not maxing
out my equipment in terms of cpu cycles, there is no harm done in erring
on the side of caution, if high sample rates don't incur higher costs as
they go through the workflow.
as a counter-example, a tv production i'm involved in uses 96k
initially, but only because the live sound desk is a midas which cannot
do less. it is immediately downsampled to 48k before going onto the
broadcast network via dante, because nobody wants to put up with the
extra data and doubled loadin/transfer times.
> And in case anyone is tempted to state that even if we don't hear them
actually, i just had a behringer ada8000 die on me, and i will probably
replace it with some 96khz capable kit from directout. i don't expect to
find anything interesting, like you said, but i'm going to try it
nonetheless. i know that my tweeters will only begin to roll off at 40khz.
i'm not advocating high sample rates, but hey, "because i can" has
always been a strong incentive :-D
the main problem is that some equipment actually gets worse at high
sample rates, and putting a 192k sticker on your box is actually more
important than getting 48k really right...
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