[KeithEmo]

That's an interesting question..... and it would apply specifically to a single impulse.

If you watch the kick drum, you'll see the drumhead move a clearly visible fraction of an inch in the forward direction when the beater hits it.
If you equate that to a 24" subwoofer moving a half inch it's clearly a significant amount of energy in one pulse.
And, considering that the drumhead and the beater are both pretty heavy, and moving relatively slowly, I would assume a significant portion of it is at a very low frequency.

Descriptions of the frequency spectrum of bass drums vary widely - and many state "as low as 20 Hz" - while many also seem to consider 30 Hz as the lowest common fundamental.
However, nobody seems to rate the energy in terms of what's present in the single starting impulse rather that what's present in the oscillation that follows it.
If we include things like those enormous Japanese Taiko drums, then I would assume that at least some go far lower.
At least some few pipe organs include one or more 16 Hz pipes.
Considering how much trouble most older speakers, and vinyl cutting lathes, have with such low frequencies, I suspect they are often deliberately filtered out.

I would note that most digital recording equipment has no trouble whatsoever with even extremely low frequencies.
However, vinyl records, and record equipment, have a lot of trouble with very low frequencies.
(Low frequencies take up a lot of track space, risk exciting mechanical resonances in the turntable and tonearm, and a lot of vinyl equipment has a deliberate low-frequency roll off to reduce rumble and record warp.)
Many speakers, especially before subwoofers became common, also had trouble with very low frequencies (excessive cone movement and very little output).
I believe many tape decks also have trouble with very low frequencies (because tape heads are inductors) - but I could be wrong there.
This suggests several reasons why many recordings, and especially older ones, probably limit their very low frequency response.)

I can see that being true of a great big tympani drum, but would the standard kick drum in a rock group put out significant levels down at 15Hz too?

I'm not looking at the theory here. I'm looking at typical music. What kind of music would have a lot of sub 20Hz content? I've played a lot with my equalizers and to me, it seems like most recorded music doesn't have a lot below 40Hz, much less as low as 15Hz. Most bass I find is between around 50Hz and 200Hz. I've found that it's rare to find anything in recorded music that goes down much lower than 40Hz. I imagine it's there in theory, but it isn't at an audible volume over the rest of the drum hit.

I realize I'm generalizing here. I'm just trying to understand where this all fits in the real world. Maybe there's a kind of music where sub bass is important and I'm just not aware of it.

 

[gargani]

Ermm, I can simply stick in a pair of halfway decent in-ear monitors and fire up a tone generator:
http://www.szynalski.com/tone-generator/

- 20Hz: easily heard / felt at normal listening levels.
- 15Hz: a little quieter, but still easily detectable as slower vibrations / deeper tone.
- 10Hz: here it gets tricky and I have to increase volume to unsafe levels to be certain.

But 15Hz... no problem at all! What am I missing here?

Ermm, I can simply stick in a pair of halfway decent in-ear monitors and fire up a tone generator:
http://www.szynalski.com/tone-generator/

- 20Hz: easily heard / felt at normal listening levels.
- 15Hz: a little quieter, but still easily detectable as slower vibrations / deeper tone.
- 10Hz: here it gets tricky and I have to increase volume to unsafe levels to be certain.

But 15Hz... no problem at all! What am I missing here?

Just tried this test with audeze lcd2c headphones. The lowest tone I could reliably hear was 22hz. The highest frequency I could hear was 14khz. (just barely).

 

[Phronesis]

Seems that some of the debate around here is about whether something is possible, likely, very likely, almost certain, or essentially certain. Which category something falls in will often be a matter of judgment, and perhaps it's best to just accept that people will reach different conclusions based on their judgment. It's often not possible to convince someone that their judgment on something is incorrect by presenting arguments, because judgment is largely intuitive rather than based mostly on arguments.

 

[Zapp_Fan]

This suggests several reasons why many recordings, and especially older ones, probably limit their very low frequency response.)

Two other reasons: Lots of energy in subsonic frequencies being present in the mix throws off compressors / limiters in that they will change output based on inaudible stuff. It can also cause clipping in a digital file by increasing the total signal amplitude without increasing the audible content, so you lose headroom for no reason. Both good practical reasons to roll off the ultra-low stuff.

Also, if you feed a speaker a loud 8hz tone, it may try to reproduce it, and use up a lot of wattage to no avail. It might even break. So given that it's a good assumption that the average listener is not going to effectively reproduce anything under 20hz, and that giving them lower frequencies might be harmful, you may reasonably remove those frequencies from the recording.

It would be very difficult to know if this has been done to a recording or not. If you look at transients it's pretty hard to get a spectrograph to resolve those low frequencies ... in fact I'm not sure if the math even works that way.

 

[gargani]

Ha! I saw what you did there! Good one!

Ha! I saw what you did there! Good one!

Ha, Ha; you got it!

 

[old tech]

My sense is that the main difference between live sound versus recordings played back on sound systems is in the acoustics, with respect to how we localize sounds, attenuation of frequencies, etc. to construct an 'auditory scene'. The live experience will always be quite different from anything played back on a sound system. That doesn't mean the sound system can't sound really good, maybe even be rated by a listener as 'better than live', but I just don't think we can replicate the live experience.

All that is true and the other major factor is that we are still stuck with transducers - eg mikes, speakers and in the case of analog recording/playback, a whole series of them.

Because the purpose of transducers is to convert one form of energy into another, there will always be losses. Even with the best digital equipment we are still stuck with mikes and speakers.

 

[KeithEmo]

Unfortunately most spectrograms are Fourier based and take a few seconds to resolve information at low frequencies....

It seems like you should be able to look at the actual waveform and confirm that the initial "bump" is positive going (the drum head moves forward first)...
And, if it's a clean half of a sine wave, you could get a read on that frequency by marking the two zero crossings and calculating the frequency from there...
However, there's a good chance that this will have been lost somewhere along the signal path and not be that clear...
(And, if that's the case, then it probably doesn't matter anyway.)

I would ASSUME that most recordings have been high-pass filtered at 15 Hz or so... if not higher... to protect speakers...
And, likewise, anything on vinyl will have been high-passed, either before being pressed to avoid super-wide tracks and resonance issues with the turntable...
Or after being played, either by an explicit rumble or warp filter, or by a quite reasonable low-frequency cutoff applied to the boost in the RIAA EQ.
As you say, very low frequencies will eat up power, and be quite dangerous to speakers, especially those with tuned ports.

Also, from what I've read, it seems widely agreed that it is the upper harmonics that impart the actual sound character to most drums.
So, as long as there's "some punch left", nobody is trying very hard to reproduce very low frequencies there anyway...
(From a practical point of view, rolling off the super-low frequencies, while boosting frequencies around 50 Hz or so, will make the sound seem "punchier" - and use less power.)

Two other reasons: Lots of energy in subsonic frequencies being present in the mix throws off compressors / limiters in that they will change output based on inaudible stuff. It can also cause clipping in a digital file by increasing the total signal amplitude without increasing the audible content, so you lose headroom for no reason. Both good practical reasons to roll off the ultra-low stuff.

Also, if you feed a speaker a loud 8hz tone, it may try to reproduce it, and use up a lot of wattage to no avail. It might even break. So given that it's a good assumption that the average listener is not going to effectively reproduce anything under 20hz, and that giving them lower frequencies might be harmful, you may reasonably remove those frequencies from the recording.

It would be very difficult to know if this has been done to a recording or not. If you look at transients it's pretty hard to get a spectrograph to resolve those low frequencies ... in fact I'm not sure if the math even works that way.

 

[bigshot]

The way to get closer to live sound is a balanced response and more channels to create a defined sound field and directionality. Inaudible or fringe frequencies and lower noise floors won't get you any closer.

 

[castleofargh]

a few opinions in a box:
- a huge concept in science is disproving things, not proving them. but still, when what's falsifiable resisted our best attempts to disprove it, our confidence sometimes increases to the point where something is simply a fact. how that happens depends on circumstances and statistics and whatever else, but it happens a lot. we can't just somehow turn all that is known as a maybe for the sake of sticking to the purest notion of science. that IMO isn't science at all. let's just take situations where what's happening can only have a known number of causes, disproving all but one of those possibilities gives us certainty. of course we need to first be sure that we're not forgetting extra possibilities, but that again will be a matter of circumstance, not a matter of philosophy. it's good to keep an eye for our mistakes and what we could have missed, that certainly is very important in science, but so are facts!

- for the few posts discussing how something in playback doesn't sound like the real instrument/event(cymbals?), as a reason to consider the lack of ultrasounds or a few other stuff missing from a recording as perhaps being the cause of that feeling. I'd like to remind you that almost no recordings are trying to be a faithful reproduction of an acoustic event. then obviously there are all the imperfections of our playback system. even more so when we're in a forum about headphones, expecting the experience to be identical on headphones is but a dream. and almost nobody is even trying, as seen by how audiophile are happy to use albums mastered for speakers and keep hating DSPs in all forms(except all those used without them knowing, then they're fine and the sound is good ^_^).

- about testing something like 15hz ourselves with headphones and IEMs, I honestly don't know if that can be called conclusive. well it can show that we're perceiving something, but is that something the 15hz sound or various consequences of it? IDK. I checked a few IEMs and perceiving 15Hz is no problem even at my usual listening levels I can still somehow perceive a tiny something even on those rolling off a bunch. but funnily enough, despite bothering to then calibrate each one to have the 15hz tone at about 85dB SPL, I subjectively thought I could notice it better on some IEMs than others. otherwise, in general I start getting a tone a little above 20Hz, below is more of a shaking and my sensitivity goes down really fast below 15hz.
I thought I was super smart and assumed I was noticing more on the IEMs with high harmonics, but turns out that one of those I notice most shows really low THD(on my measurements) and even trying to look for something with the RTA while sending 20 or 15Hz, I couldn't see anything suspicious. so I'm not sure if it might have to do with how stuck the IEM is in my ear, or maybe how heavy they are so they wobble with the signal? or probably more likely, how good a seal I end up getting in my ear with each? IDK. I now have way more questions than I had when I decided to spend half an hours fooling around with IEMs. my Fiio EX1 are as vented as it gets and I perceive 15Hz super clearly @85dB SPL. but then the level was measured vented from the start. so despite now knowing that I don't need solid occlusion to feel 15Hz, that doesn't exclude that I might get a different seal in my coupler when I calibrate the levels compared to in my own ears. in conclusion, IDK and as often, I have more questions after my tests than before. ^_^

 

[analogsurviver]

a few opinions in a box:
- a huge concept in science is disproving things, not proving them. but still, when what's falsifiable resisted our best attempts to disprove it, our confidence sometimes increases to the point where something is simply a fact. how that happens depends on circumstances and statistics and whatever else, but it happens a lot. we can't just somehow turn all that is known as a maybe for the sake of sticking to the purest notion of science. that IMO isn't science at all. let's just take situations where what's happening can only have a known number of causes, disproving all but one of those possibilities gives us certainty. of course we need to first be sure that we're not forgetting extra possibilities, but that again will be a matter of circumstance, not a matter of philosophy. it's good to keep an eye for our mistakes and what we could have missed, that certainly is very important in science, but so are facts!

- for the few posts discussing how something in playback doesn't sound like the real instrument/event(cymbals?), as a reason to consider the lack of ultrasounds or a few other stuff missing from a recording as perhaps being the cause of that feeling. I'd like to remind you that almost no recordings are trying to be a faithful reproduction of an acoustic event. then obviously there are all the imperfections of our playback system. even more so when we're in a forum about headphones, expecting the experience to be identical on headphones is but a dream. and almost nobody is even trying, as seen by how audiophile are happy to use albums mastered for speakers and keep hating DSPs in all forms(except all those used without them knowing, then they're fine and the sound is good ^_^).

- about testing something like 15hz ourselves with headphones and IEMs, I honestly don't know if that can be called conclusive. well it can show that we're perceiving something, but is that something the 15hz sound or various consequences of it? IDK. I checked a few IEMs and perceiving 15Hz is no problem even at my usual listening levels I can still somehow perceive a tiny something even on those rolling off a bunch. but funnily enough, despite bothering to then calibrate each one to have the 15hz tone at about 85dB SPL, I subjectively thought I could notice it better on some IEMs than others. otherwise, in general I start getting a tone a little above 20Hz, below is more of a shaking and my sensitivity goes down really fast below 15hz.
I thought I was super smart and assumed I was noticing more on the IEMs with high harmonics, but turns out that one of those I notice most shows really low THD(on my measurements) and even trying to look for something with the RTA while sending 20 or 15Hz, I couldn't see anything suspicious. so I'm not sure if it might have to do with how stuck the IEM is in my ear, or maybe how heavy they are so they wobble with the signal? or probably more likely, how good a seal I end up getting in my ear with each? IDK. I now have way more questions than I had when I decided to spend half an hours fooling around with IEMs. my Fiio EX1 are as vented as it gets and I perceive 15Hz super clearly @85dB SPL. but then the level was measured vented from the start. so despite now knowing that I don't need solid occlusion to feel 15Hz, that doesn't exclude that I might get a different seal in my coupler when I calibrate the levels compared to in my own ears. in conclusion, IDK and as often, I have more questions after my tests than before. ^_^

Almost ?

Never caught a rabbit.

 

[Phronesis]

a few opinions in a box:
- a huge concept in science is disproving things, not proving them. but still, when what's falsifiable resisted our best attempts to disprove it, our confidence sometimes increases to the point where something is simply a fact. how that happens depends on circumstances and statistics and whatever else, but it happens a lot. we can't just somehow turn all that is known as a maybe for the sake of sticking to the purest notion of science. that IMO isn't science at all. let's just take situations where what's happening can only have a known number of causes, disproving all but one of those possibilities gives us certainty. of course we need to first be sure that we're not forgetting extra possibilities, but that again will be a matter of circumstance, not a matter of philosophy. it's good to keep an eye for our mistakes and what we could have missed, that certainly is very important in science, but so are facts!

The problem with calling things 'facts' is that they become assumed to be absolutely proven truths. Philosophically, I don't think we can get there. And sometimes 'facts' later turn out to not be facts after all.

But if we say 'facts' are more like 'things which have, relative to a belief system, been found to be consistently accurate, and consistently never inaccurate, based on a large range of experience, or can be logically derived from such things, and therefore can be assumed to be true in practice', then I'd be ok with saying there's such a things as facts.

 

[bigshot]

I'm wondering if the ability to "hear" 15Hz with IEMs has something to do with the proximity of the transducer to the inner ear and the seal bottling up the vibrations. Maybe the rumble caused by the low wavelength in close contact with our inner ear makes something inside our ears "rattle" and creates audible low frequency distortion in our ears. I know my subwoofer is rated to 14Hz or something like that, and I've heard it go low enough that it's just a vibration that can be felt in the air, not a sound that can be actually heard. It could also be that it takes far less energy to create sub bass sealed in your ear canal than it does to fill a room with it. Perhaps the energy dissipates fast. Or maybe in free space the waves are as long as a truck and start bouncing off the walls and breaking up. Not sure. I'll think about it. It's an interesting observation.

 

[Phronesis]

That is an excellent point.

There is a huge gap between when our sensory organs detect inputs and when our brains perceive something. This is especially complex when we talk about music because the connections themselves are quite complex. For example, when you hear a violin, what does your brain "perceive"?

The way our brains process input is IMMENSELY complicated..... so, for example, you may feel something, or taste something, or "see something in your mind" when you hear a certain sound. And, to make matters even worse, the details of this process vary wildly between individuals.

A casual listener might perceive "a violin playing", while a musician perceives the printed score the musician is playing, a mathematician perceives a sequence of numbers, and a scientist might perceive an image of what the spectrum would look like on a graph. And, inside their brains, the musician might see finger placements, or a printed musical score, while the mathematician sees equations printed on a page, an art student might even see the field of flowers the composer was thinking of when she wrote the piece, while Charlie might smell the perfume of the girl he was with the last time he heard it. And ALL OF THOSE ARE VALID RESPONSES.

(And, if there's a flaw in the recording, the mathematician may "see" an error in an equation, the musician might see fingers in the wrong place, the artist might notice that the flowers in her image seem a bit fuzzy, and it may FAIL to evoke feelings of his first love in Charlie - because it's a poor match for the pattern required to do so. And, unfortunately, none of that stuff can be measured.)

I'm actually taking it further, viewing perception as mental rather than physical. Which raises a standard problem in philosophy, the problem of consciousness - how something non-physical (mind) can be linked with something physical (brain and body). I don't know the answer, no one else has figured out the answer, and I have some doubt that we humans can figure it out. Scientists try to work with 'neural correlates of consciousness' (NCCs), but they're only correlates, not the thing itself.

It can be argued that this takes us beyond science (I think it does), but if people are talking about 'what they hear' and 'what sounds good' and 'it sounds different' and 'it sounds the same', that's all mental perception stuff, and we somehow need to tie that back to physical sound and gear in a meaningful way. And I do think the philosophical perspective can have some practical value here, because if we look at the 'phenomenology of perception', by studying the character of perception as we subjectively experience it, that can provide some suggestions on how to select NCCs and design experiments based on them.

From Wikipedia: https://en.wikipedia.org/wiki/Hard_problem_of_consciousness

In Facing Up to the Problem of Consciousness (1995), Chalmers wrote:[3]

It is undeniable that some organisms are subjects of experience. But the question of how it is that these systems are subjects of experience is perplexing. Why is it that when our cognitive systems engage in visual and auditory information-processing, we have visual or auditory experience: the quality of deep blue, the sensation of middle C? How can we explain why there is something it is like to entertain a mental image, or to experience an emotion? It is widely agreed that experience arises from a physical basis, but we have no good explanation of why and how it so arises. Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does.​

I have some further thoughts on all of this which I'll elaborate later.

 

[Phronesis]

I'm wondering if the ability to "hear" 15Hz with IEMs has something to do with the proximity of the transducer to the inner ear and the seal bottling up the vibrations. Maybe the rumble caused by the low wavelength in close contact with our inner ear makes something inside our ears "rattle" and creates audible low frequency distortion in our ears. I know my subwoofer is rated to 14Hz or something like that, and I've heard it go low enough that it's just a vibration that can be felt in the air, not a sound that can be actually heard. It could also be that it takes far less energy to create sub bass sealed in your ear canal than it does to fill a room with it. Perhaps the energy dissipates fast. Not sure. I'll think about it. It's an interesting observation.

I'm thinking along the same lines, and somewhat skeptical that the ear is actually transducing 15 Hz signals.

 

[Davesrose]

I'm thinking along the same lines, and somewhat skeptical that the ear is actually transducing 15 Hz signals.

The cochlea does have waves that propagate below 20hz (and can stimulate). They may be part of perception, but are not considered within the range of discriminating pitch.