I'm sorry... but I do see what's going on here...
I seem to be talking about scientific measurements....
While you seem to be trying to bring in a bunch of stuff that, while it may pertain to recording in many situations, is not directly related.
If I take two sources, in a totally open space, or an anechoic chamber (to eliminate outside factors)...
All frequencies will drop off
EQUALLY due to the inverse square...
IN ADDITION TO THAT, at two meters, 30 kHz will lose an additional 1.8 dB due to air absorption.... (at 20 degrees C, at sea level, at 50% RH)
While low frequencies, for example 200 Hz, will lose virtually nothing due to air absorption....
(Therefore, my recording at two meters will be "down 2 dB at 30 kHz" compared to flat.)
And,
IF YOU CAN FIND ENOUGH LEVEL TO RECORD AUDIBLE FREQUENCIES AT 20 METERS.....
The level at all frequencies will be significantly lower - based on the inverse square of the distance.
But, in addition to that loss in level, the level at 30 kHz will be an additional 18 dB lower than the level at 200 Hz.
(So, regardless of the overall level, it will then be "down 18 dB at 30 kHz relative to flat".)
Now, remember that we're talking about direct incident sound, so no room reflections, and no "acoustic contributions".
(I would definitely expect to see a much greater loss at 30 kHz if we take our measurements in a real room - and use a long enough window to include reflected sound and other "room contributions".)
Likewise, when we're talking science, we tend to look at things a bit differently.
For example, when I talk about measuring frequencies, I don't have to concern myself with the limitations of the microphone you would choose to use.
I have no reason to doubt it when you say that you would never mic a drum kit with a condenser microphone.
And I have no reason to doubt that the dynamic microphone you would choose, based on several considerations, like good sound quality, won't pick up 30 kHz.
HOWEVER, here's a cute little microphone:
http://www.pcb.com/products.aspx?m=378A14
It has a rated frequency response from 4 Hz to 70 kHz (+/- 2 dB)
It also has an inherent noise of 50 dB, and a dynamic range of 173 dB.
From those numbers, my guess is that, with a proper preamp, it would have no trouble recording a snare drum, or a cymbal, from an inch away (or from two meters away).
And, at that range, it will record everything up past 70 kHz.
(So doing so is not only theoretically possible; it's actually possible with currently available equipment.)
It's not my problem if you don't happen to have one of these in your studio to take your measurements with...
And, as the recording engineer, it's your choice to choose not to use it if you don't think it sounds good...
HOWEVER, neither of those facts is relevant if we're discussing what's
possible...
So, for the sake of
SCIENTIFIC DISCUSSION.....
If I record that cymbal from two inches away... using that microphone... I will get a very accurate recording (+/- 2 dB from 4 Hz to 70 kHz).....
(We'll assume that I'm doing it in a free field, or an anechoic chamber, to exclude room acoustics and other outside influences.)
And, if I then do it again from two meters away, I will find that the level at 30 kHz is down by about 1.8 dB (compared to the level at 200 Hz)....
Therefore, I have shown that is is possible to do so, and, beyond that, that the equipment required to do so is currently available....
That satisfies the requirement of "proving that it's possible".... which is all that I stated to begin with.
And, while I've seen a wide variety of estimates, everyone seems to agree that cymbals produce sound well above 25 kHz.
(And breaking glass, which has been featured on more than a few albums, has measurable frequency components extending past 50 kHz.)
I am perfectly willing to concede to you things like....
- nobody ever does it that way
- no recording studio you know currently has the equipment required to do it
- it would probably sound bad anyway (or not sound especially good)
- it wouldn't be what somebody sitting in the audience would hear
I would again remind anybody coming in late that what we're discussing here is the possibility of recording cymbals and including spectral content at ultrasonic frequencies.
We are
NOT discussing whether that would be
audible or even whether it would be
desirable... simply that it would be
possible.
(We are discussing
SCIENCE and
NOT good recording technique.....)
I should also point out, just to make
@bigshot happy, that, if we're talking about "results of test performed by thousands of recording engineers all over the world",
then it seems like we should have plenty of properly documented test data to look at. (Otherwise that would all just be "a lot of anecdotal evidence".)
Many audiophiles make claims which are ridiculous because they not only simply ignore all the laws of physics but actually contradict them. You on the other hand are quoting one of the laws of physics, but it's still as effectively invalid because you are ignoring all the other pertinent laws of physics and then FALSELY asserting (twice) "that's what the ones in this universe say". Unless you're living in a different universe, that is absolutely NOT what the laws of physics in this universe say. So not only is your statement FALSE but as I've posted in response to you more than once what the relevant laws of physics are, and actually given you facts and figures, then you cannot claim ignorance or being "inadvertently" mistaken. This is the science forum and therefore pretty much the exact opposite of the "let's ignore and/or misrepresent the science (as suits our agenda)" forum!
For those interested in ALL the relevant facts/science:
We have to consider the practicalities/realities of recording, not just an individual law/rule of physics but the COMBINATION of variables, such as: What is being produced in the first place, what mics are capable of, how do they need to be employed in practice, what laws of physics apply and how do they apply. For example, a snare drum in a drumkit is virtually always very closely mic'ed, so if we're talking about recording from say 2-3m away (in the overhead mics) we not only have to take into account the inverse square law (which KeithEmo is TOTALLY ignoring) but also apply it appropriately, as the inverse square law deals with RELATIVE distance.
@Arpiben and
@Zapp_Fan - You might find this online calculator useful as it deals specifically with relative mic distance:
http://www.sengpielaudio.com/calculator-distance.htm. If we enter 0.0254 (1 inch) into ref (mic) 1 and 2.5m into ref (mic) 2, we see that the SPL at 2.5m is almost 40dB (roughly 100 times) lower. Turning this around, if we had say 100dBSPL at 2.5m (which is not at all unreasonable for a snare drum hit), we would have 140dBSPL at the mic position of 1 inch. Now, we MUST COMBINE this fact with "what mics are capable of" and here we run into a problem because most studio condenser mics are only capable of a maximum level of around 130dBSPL, so we would get break-up distortion (and possibly physically damage the mic). For this reason, we would typically use a dynamic mic for the snare drum in a kit as they can cope with the high SPLs BUT, compared to condenser mics, dynamic mics have very poor high frequency response, typically with a roll-off starting around 9kHz-10kHz and listed with a response extending typically to around 15kHz (they may pick-up content above the freq response spec but at extremely reduced levels). The same is true of any instrument of course, not just the snare drum, although with other instruments we may have additional factors to consider (such as proximity effect for example). In ADDITION to the inverse square law, we have the physics rule/law of thermal noise which comes into play when mic'ing at a distance (even of 2.5m), which increases with frequency. Using the example above, to achieve the same output level from the mic at 2.5m (as at 1 inch) we would need to amplify the mic's output by 40dB, which would also increase the noise floor of the mic and mic-preamp by 40dB but in addition, at 20kHz we've got approximately 22dBm more thermal noise (power) than at say 100Hz. In addition again, we have the one law of physics KeithEmo did bother to quote (HF air absorption) and of course we also have to consider the amount of ultrasonic freq content we have in the first place, what the instrument is actually producing. In practice many instruments have no ultrasonic content but, as has been evidenced by the Boyk paper (which has been linked to several times), those that do typically only produce tiny fractions of a percent of their energy in the ultrasonic band and even only around 6% for the cymbals, which of all instruments probably produces the highest amount of ultrasonic content. So, we've got relatively little utrasonic content to start with, PLUS a higher noise floor.
If you "join the dots" of all this information: We pretty much always use condenser mics for the overheads when mic'ing a drumkit, because they have far lower SPLs to deal with than the close mics and they can more accurately capture the >9kHz content. Obviously though, the final sub-mix of the drumkit will not be comprised of only the overhead mics' output, it will also contain the close mics' output and commonly also the output of a room mic (at a much greater distance than 2.5m and therefore with significantly lower ultrasonic content). BTW, I've essentially already stated ALL of this in previous posts in this thread!
Do I really need to qualify my numbers with "in this universe"? I haven't quoted numbers for your alternate universe in which the only laws of physics that exist are the ones which support your agenda! In this universe those numbers ARE correct!
For everyone else (in this universe!): The numbers vary according to distance and other factors. For example, cymbals are not only used in popular music. In an orchestra for example the main mics will typically be around 10m from the cymbals so we'll get significantly more ultrasonic freq loss but we commonly we use a specific type of mic which is spec'ed to 14kHz and again, there will be multiple mic's (including room mics) all mixed with the main mics. However, the ideal audience position is at least 20m from the cymbals, probably closer to 30m. The ultrasonic freq loss at that distance plus the raised noise floor of the mic (if we were to record from that ideal position) would result in there not being ANY recordable ultrasonic content from the cymbals (or any other instrument).
1. I stated
at that time almost no studio mics went that high. Today, largely because of false marketing, there is more of a requirement to demonstrate the presence of content >20kHz and therefore more mics that cater to that requirement.
2. No, that is a
blatant lie "inadvertent" error, which doesn't even make any sense according to your own quote. If "most studio mics don't go that high" then there must be a few which do (only one or two at the time), we used those which did, duh! Also, because even those that did weren't much good above 20kHz we also tried with other laboratory/test mics.
3. We did and they couldn't! Furthermore, as I've already made CLEAR, we are not talking about one test that I did, we're talking about numerous tests that thousands of independent sound engineers carried out all over the world and repeated various/numerous times.
4. What "arguing about the laws of physics"? There are NO rational arguments about the laws of physics, only irrational arguments by audiophiles who don't actually even know the laws of physics or snake oil salesmen trying to misrepresent them! Now that we've demonstrated that you were misrepresenting the laws of physics, all of a sudden it all "seems to be a sort of a waste of time to you" ... of course it does!
Or in fact nothing like that whatsoever. OK then: This whole discussion is really a sort of detour associated with
@KeithEmo asserting that unicorns exist and pigs can fly (or something like that).
No, it's not! If consumers are demanding to pay only a fraction of a cent (or nothing at all) for their recordings and therefore labels and artists are only spending a fraction of the time and money on making recordings, how's that the job of a recording engineer to fix?
If a mousetrap is already effectively perfect then all we're left with, as you say, is to make another mousetrap and "simply convince their customers that it's better", IE. Marketing! Falsely convince customers that their perfect mousetrap isn't in fact perfect by lying about what "perfect" means, lying about the laws of physics, lying about the realities and practicalities of mousetraps, etc.
1. Clearly that's an obvious contradiction. If one of the indicators of relative distance from the source is the attenuation of ultrasonics, then attenuating ultrasonics MUST sound natural!
2. A muted trumpet produces about 0.03% of it's energy above 20kHz, beyond 80kHz obviously far less and that's at just 1m, so how exactly is that "specially rich in ultrasonics beyond 80kHz"? And you stated that the trumpet wasn't muted, so your "specially rich" is actually nothing whatsoever!
3. And that amplification extended to 80kHz did it? What super-tweeters were they using at this live gig?
4. A pretty good picture of what exactly up to 48kHz? A pretty good picture of what an un-muted trumpet and an amplification system isn't producing?
We could solve so many of these utterly ridiculous assertions and arguments by simply having an "Alternate Universe Sound Science" forum!!
G