[dprimary]

I'm kind of looking at all this from the opposite direction.

Most people I know agree that, even if you're standing on the sidewalk, listening through an open window, you can usually tell the difference between a live band playing and a recording. And I find the distinction to be especially vivid when someone inside the room whacks the cymbals really hard. Therefore, clearly, we are FAR from able to make a recording that accurately replicates the live performance.

I disagree. I have had many occasions that someone thinks a person is playing when they can't see in the room the sound is coming from. Most of the time you know it is not a live performance. If I have the front door open you are pretty sure the Stones are not rehearsing in my living room, you are also sure a orchestra will not fit. If you are playing a recording of a rehearsal or play back of recording that is unfamiliar to the listener and at realistic SPL it does not even need to be that good of full range loudspeaker to fool people. I have also walked out of my door thinking two houses down is playing the stereo pretty loud to see no there is a few people on porch playing.

 

[Phronesis]

I disagree. I have had many occasions that someone thinks a person is playing when they can't see in the room the sound is coming from. Most of the time you know it is not a live performance. If I have the front door open you are pretty sure the Stones are not rehearsing in my living room, you are also sure a orchestra will not fit. If you are playing a recording of a rehearsal or play back of recording that is unfamiliar to the listener and at realistic SPL it does not even need to be that good of full range loudspeaker to fool people. I have also walked out of my door thinking two houses down is playing the stereo pretty loud to see no there is a few people on porch playing.

Could be that people just vary in this respect. I can almost always tell when music in my environment is live, but my wife can't tell nearly as accurately. However, an alternate hypothesis is that I'm discerning the difference more based on the quality of the music performance rather than the sound.

 

[Zapp_Fan]

In any case, frequencies that low probably don't exist at audible levels in most recorded music. I think a pipe organ is the only instrument that goes that low. And the main benefit of sound that low in movies is to create the kinesthetic thump in your chest along with explosions and stuff like that.

This is not quite right. All transients (drum hits in particular) contain all frequencies from DC to infinity, to the extent that they resemble a true zero-duration/Dirac impulse. So the less highpass filtering (or... any filtering at all) you have, the better transients will be, generally speaking. Now, there are good reasons to highpass stuff and it's not unusual for a recording to be highpassed either... but it's not as if there's no point to reproducing frequencies below the lowest musical note's fundamental frequency.

 

[bigshot]

I have had many occasions that someone thinks a person is playing when they can't see in the room the sound is coming from. Most of the time you know it is not a live performance. If I have the front door open you are pretty sure the Stones are not rehearsing in my living room, you are also sure a orchestra will not fit. If you are playing a recording of a rehearsal or play back of recording that is unfamiliar to the listener and at realistic SPL it does not even need to be that good of full range loudspeaker to fool people. I have also walked out of my door thinking two houses down is playing the stereo pretty loud to see no there is a few people on porch playing.

Back in the teens when recording was in its infancy, Thomas Edison would conduct blind "Tone Tests" in vaudeville theaters. The test consisted of a singer on stage singing a song. The lights would go out making the whole theater pitch black. When the lights came on, the singer would be gone and an Edison Laboratory model C-19 would be singing the song. During the blackout, they would switch off in a pause between verses. Contemporary reports were all favorable. People were astonished that a phonograph could exactly duplicate a human voice.

The problem with discerning live from "Memorex" depends more on the directionality of the sound than it does the fidelity. The horn of a phonograph was very close to the way a human voice projects. The Edison engineers would position the horn so it lined up closely with the singer, so when it handed off, the directionality wouldn't change. The natural acoustics of the vaudeville theater would wrap the same acoustic around the phonograph that it did around the singer. The wall reflections and reverb were all identical because the recording was dry, just like the voice.

I've heard that some antique phonograph fans have recreated Edison Tone Tests and have gotten similar results.

 

[gregorio]

[1] In my own area of engineering, our models are usually not as good as models based on circuit theory, but the assumptions based on Newtonian mechanics are effectively treated as being certain and we lose no sleep over that.
[2] With audio, it's when we bring listeners and perception into the models, as with any type of listening test, that things get messy and the effects of even very tiny differences in gear wind up introducing a sliver of uncertainty and open the door to debates.

1. Yep, Newtonian mechanics is another good example of theory that's since been refined but except in extreme circumstances we can treat it as if it were certain. The work of Fourier (for example) we can treat as even more certain because in nearly 200 years it hasn't even needed any refinement.

2. True but things only get messy to an extent, we can still end up with a high degree of certainty. For example, an average fit 20 year old could probably run 100m in 15-20 seconds and 11-13 secs with training, the ultimate human achievement so far is 9.58 seconds but that's still rather messy, it maybe possible to achieve 9.5, even 9.0 might be possible, although it seems rather unlikely. But what about 0.95 secs, can't we effectively treat that with a "certainly" of not possible or what about 0.009 secs? To use KeithEmo's analogy, how about someone lifting 300 tons or 3000 tons? We can easily measure the difference between two cables (for example) and those differences are in the order of a hundred to a thousand times smaller than anyone had ever demonstrated the ability to detect. Are we to believe an audiophile is performing the auditory equivalent of running 100m in 0.09secs or can lift 300 tons? Or, do we treat it as a certainty that they're not hearing what they believe they're hearing?
With ultrasonics we have a different scenario but effectively the same end result. We know that under certain circumstances some people can hear above 20kHz but what if we deliberately screw-up those circumstances, so instead of say a pure 22kHz tone at 110dBSPL we give them a 110dB fundamental at say 4kHz with a full complement of harmonics, including a high order (22kHz) harmonic that's 100-10,000 times lower in level than the (110dB) fundamental and many times lower than the other harmonics, what do you think would happen? First of all, we couldn't even run that test, it would be too uncomfortable/painful, we'd have to lower the level by around ten times! But even if we could, we already know no one has ever demonstrated the ability to hear even a pure 22kHz tone at only 70dB (let alone at 30dB) but in the presence of a far higher level fundamental and set of harmonics, it would be like asking Usain Bolt to run 100m in 9.58 seconds, in a sack race! Do we not have something we can treat as a certainty here? And let's not forget, this isn't just theory, I and countless other engineers have tested this.

Therefore, my assertion is simply "something isn't perfect yet" - so let's find out what it is.

Why, what's the point, when we already know "what it is" and have done for at least 6 decades?

G

 

[bigshot]

This is not quite right. All transients (drum hits in particular) contain all frequencies from DC to infinity, to the extent that they resemble a true zero-duration/Dirac impulse. So the less highpass filtering (or... any filtering at all) you have, the better transients will be, generally speaking. Now, there are good reasons to highpass stuff and it's not unusual for a recording to be highpassed either... but it's not as if there's no point to reproducing frequencies below the lowest musical note's fundamental frequency.

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.

 

[Zapp_Fan]

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.

Technically, yes, in theory all transients include energy down to DC, although again it depends to what extent the attack of the drum hit resembles a "true" impulse. And, it won't be very easy to detect since it's transient in nature, so I think the difference would be feeling that the bass drum's attack was slightly 'fuller' or stronger somehow, but in terms of the color of the transient (meaning, as far as you can hear it) the effect will be pretty iffy at best. It's not that you would notice it as distinct from the rest of the drum hit, it's just a component of the character of the first few miliseconds of the drum hit. Most of the decay of a bass drum is usually (as you note) somewhere in the 40+ range and usually more like 60-100.

Counter-intuitively, the most infrasound will be in the "click" portion of the bass (or other) drum attack, which will sound louder / stronger with them... if it sounds different at all. The drum won't be resonating at infrasound frequencies, so the presence of 0-20hz content is over very quickly and only contributes to the transient portion of the waveform.

In the time domain this will pretty much just show up as a higher peak on the attack of the bass drum... and only if the infrasound was really captured in the first place, which is not assured by any means.

To put it another way, you can't represent a true impulse (i.e. the sharp attack of any instrument, glockenspiels to tympanis) in the frequency domain if you're missing frequencies, because a theoretical impulse has infinite bandwidth and zero duration. IMO some drum hits are close enough to true impulses that you might want to keep subsonics just for the sake of realism, but on the other hand, I think many engineers (sensibly) filter those out to avoid screwing up other more important things. I think if you have a recording with lots of infrasound in it, it's most likely to be rumble from various things moving around and will only serve as a mysterious source of distortion.

It's another somewhat academic distinction, but I would say compared to ultrasound, infrasound has a massively better chance of affecting your listening experience. But as always with extreme cases, many planets have to align properly for the effect to matter.

 

[james444]

If I jack up the output of my headphone amp, a lot of IEMs can create some perceptible effect at 15hz. To me it basically sounds like a rapid flapping / whooshing noise. I think it's actually just periodic pressurization of my ear canal and not what might be (if any such sound can be) perceived as a tone.

I think 20hz is a practical lower limit because it's roughly the threshold where most things stop sounding like continuous tones and start sounding like periodic distinct sonic events.

Of course it's periodic pressurization of the ear canal, because IEMs form a direct coupling to the eardrum. As frequency gets lower, pressurization cycles decrease and you start noticing individual cycles, much like your vision starts noticing individual frames as you decrease the frame rate of a video. Personally, I have to go up as high as 40Hz until things really start sounding like continuous tones.

Still, I hear these low frequencies as tones, not noise. Just not as smooth, continuous tones. And I can easily tell that 15Hz is lower than 20Hz, which I couldn't, if both were just perceived as different forms of noise.

That's interesting. Can you hum the tone at a higher pitch and figure out what the musical note is? I can't do that with anything anywhere close to that frequency. Down low, I can detect a difference between one frequency and another, but not the musical pitch. Are you a musician or do you have perfect pitch? That might explain it.

See above. No, I can't. But I can distinguish these frequencies from noise, and I can tell which one of two given frequencies is lower or higher.

 

[Zapp_Fan]

Still, I hear these low frequencies as tones, not noise. Just not as smooth, continuous tones. And I can easily tell that 15Hz is lower than 20Hz, which I couldn't, if both were just perceived as different forms of noise.

This might be an issue of semantics around the word 'tone'. In my mind, a "tone" needs to be perceived as a unitary and continuous sound. I would say that 15hz is clearly "slower" than 20hz but not necessarily "higher" because I personally don't get a pitch out of 15hz. But YMMV of course, honestly I have never bothered to look into perception of tones at the bottom of the spectrum. I just took 20ms/20hz as a good rule of thumb and moved on with my life. (20ms = minimum duration needed to perceive a tone vs. just a burst of sound, so they say)

 

[KeithEmo]

That makes sense.... and also note that human voice has a relatively narrow frequency response, so wouldn't strain even the relatively narrow frequency range of an Edison phonograph.

I would also suggest that they were taking advantage of several known human bias mechanisms.

First off, we humans have a strong tendency to assign things to known and familiar categories. For example, we are all familiar with the saying about "when you hear hooves, you think horses, and not zebras". What nobody even bothers to mention is that you don't even consider ten legged robots wearing horseshoes. Instead you choose from among things you are familiar with. When the Edison phonograph was debuted very few people had ever experienced a machine that could reproduce human voice. Therefore, when hearing human voice, everyone assumed they were listening to a human singing. Since most of the participants had never experienced any other source of human voice, when they heard a human voice, they were essentially faced with the single option of assuming that they were listening to a human. And, having made that choice, they then became biased to notice details that tended to support that choice, and to tend not to notice details that were dissonant with it.

From their point of view, they never actually even evaluated the situation. What they experienced was a human singer they could see, followed by "something they couldn't see that sounded very much like the human singer". They had no specific reason to suspect that the human singer was no longer singing, and they had no experience whatsoever with anything that might have served as a replacement, therefore, based on that knowledge, the only logical conclusion was that "'the singer was still singing". They essentially had no compelling reason to doubt that, no compelling reason to consider alternatives, and no alternatives to consider even if they had wanted to.

If you or I were to hear an Edison recording today, we would notice all sorts of minor discrepancies, like noise, and speed variations, and even the occasional tick or pop, which to us would represent obvious clues that we were listening to a flawed recording. However, consider someone who had never heard those sorts of flaws before, and furthermore had already decided that they were listening to a human performer.

All of those discrepancies that we would take as obvious clues that we were listening to a recording would have little or no similar meaning for them. To them, that noise might sound like slightly noisy steam heat, the speed variations could be a slightly odd mannerism of the performer, and the ticks and pops might represent noises made by machinery backstage, or by someone in the audience dropping something. However, because we are familiar with recording technology, and the sorts of flaws common in older recording equipment, we would take them as "obvious clues" that we had switched over to a recording.

They would have been "thoroughly primed" to think they were listening to a human singer.
And they would have no experience whatsoever with the clues that might indicate a mechanical reproduction.
Therefore they would have no reason to suspect that the singer had been replaced.

Or, to put it another way, since they had never heard a phonograph before, they had had no opportunity to learn how to tell the difference between a phonograph and a human performer. And, because of that lack or training, they simply overlooked the clues that would have been obvious to a trained observer.

(One might imagine that an aborigine who was totally unfamiliar with modern technology might run screaming from a black and white video of an attacking lion - because, to him, the similarity of the experience to actually being attacked by a lion would far outweigh the differences... and the differences which would be obvious to us would have no clear meaning to him. And, if you asked him later, he would probably reply that the black and white two dimensional moving image "looked pretty much like a real lion to him" and "he had no reason to suspect it wasn't a real lion".)

Back in the teens when recording was in its infancy, Thomas Edison would conduct blind "Tone Tests" in vaudeville theaters. The test consisted of a singer on stage singing a song. The lights would go out making the whole theater pitch black. When the lights came on, the singer would be gone and an Edison Laboratory model C-19 would be singing the song. During the blackout, they would switch off in a pause between verses. Contemporary reports were all favorable. People were astonished that a phonograph could exactly duplicate a human voice.

The problem with discerning live from "Memorex" depends more on the directionality of the sound than it does the fidelity. The horn of a phonograph was very close to the way a human voice projects. The Edison engineers would position the horn so it lined up closely with the singer, so when it handed off, the directionality wouldn't change. The natural acoustics of the vaudeville theater would wrap the same acoustic around the phonograph that it did around the singer. The wall reflections and reverb were all identical because the recording was dry, just like the voice.

I've heard that some antique phonograph fans have recreated Edison Tone Tests and have gotten similar results.

 

[gargani]

Some interesting stuff about the psychology of self justification.
https://www.newyorker.com/magazine/2017/02/27/why-facts-dont-change-our-minds

It's pretty easy to tell when you run across a person who is so deeply invested in being right, they're willing to be wrong to prove it... There is a desperation to their arguments. They fly all around, never sticking to a single point. They repeat points that are clearly not true over and over to try to make them stick. They say evidence that doesn't support them is vague and not convincing while cherry picking the most vague and unconvincing arguments to put forward to support their own position. At its core, extreme self justification is a hard layer of high self esteem protecting an inner core of low self esteem. Engaging with them on a peer level inevitably leads to hostility and outright attempts at deception, because they won't allow themselves to consider anyone a real peer. That's why it's ironic that these people always seem to team up with other people with similar need for self justification to tear down each other's perceived opponents. I find that when I run across someone like this, it's best to just background them and only speak with the people who are willing to discuss issues fairly.

Thanks for the link to that article. Very interesting. It basically justified the belief I already held, about people holding on to beliefs regardless of strong evidence to the contrary.

 

[james444]

This might be an issue of semantics around the word 'tone'. In my mind, a "tone" needs to be perceived as a unitary and continuous sound. I would say that 15hz is clearly "slower" than 20hz but not necessarily "higher" because I personally don't get a pitch out of 15hz. But YMMV of course, honestly I have never bothered to look into perception of tones at the bottom of the spectrum. I just took 20ms/20hz as a good rule of thumb and moved on with my life. (20ms = minimum duration needed to perceive a tone vs. just a burst of sound, so they say)

Agreed, but imho semantics isn't important in that context anyway. This started out as a discussion on human hearing range, and regardless of whether we hear 15Hz as "tone" or just a "burst of sound", it's definitely something we can hear with IEMs.

For example, I keep reading, over and over again, how "human hearing extends from 20 Hz to 20 kHz".
But, a few months ago, I read that, under certain lab conditions, it has been PROVEN that 10 Hz is audible.
Several studies are also underway in the EU about how "subsonic sounds" from wind farms affect people.
Therefore, what can I logically conclude, except that the oft-quoted "20 Hz to 20 kHz" range is wrong after all?
Those damn lab scientists screwed it up again.
THAT is the hazard of making overreaching generalizations.

 

[KeithEmo]

I'm not seeing the comparison here.....

The fastest human runner in 1860 could run a mile in about 4:45
Today the fastest runner can do it in just under 3:43

The land speed record for wheeled vehicles is 7.5x as fast today as the record in 1905.

And we now know that the lower frequency limit for hearing is 12 Hz and not the previously believed 20 Hz.
(And that's presumably just due to limits or errors in previous experiments.)

Considering that 30 kHz is only 50% above 20 kHz...
And we already know that some people can hear beyond 20 kHz...
It just doesn't seem especially unlikely to me.

Personally, I don't know either way...
I just can't figure out how some other people can be so absolutely positively sure...

If it makes you happier I will "concede" that it probably doesn't matter much.
(But that still falls short of being able to call it a certainty... sorry.)

1. Yep, Newtonian mechanics is another good example of theory that's since been refined but except in extreme circumstances we can treat it as if it were certain. The work of Fourier (for example) we can treat as even more certain because in nearly 200 years it hasn't even needed any refinement.

2. True but things only get messy to an extent, we can still end up with a high degree of certainty. For example, an average fit 20 year old could probably run 100m in 15-20 seconds and 11-13 secs with training, the ultimate human achievement so far is 9.58 seconds but that's still rather messy, it maybe possible to achieve 9.5, even 9.0 might be possible, although it seems rather unlikely. But what about 0.95 secs, can't we effectively treat that with a "certainly" of not possible or what about 0.009 secs? To use KeithEmo's analogy, how about someone lifting 300 tons or 3000 tons? We can easily measure the difference between two cables (for example) and those differences are in the order of a hundred to a thousand times smaller than anyone had ever demonstrated the ability to detect. Are we to believe an audiophile is performing the auditory equivalent of running 100m in 0.09secs or can lift 300 tons? Or, do we treat it as a certainty that they're not hearing what they believe they're hearing?
With ultrasonics we have a different scenario but effectively the same end result. We know that under certain circumstances some people can hear above 20kHz but what if we deliberately screw-up those circumstances, so instead of say a pure 22kHz tone at 110dBSPL we give them a 110dB fundamental at say 4kHz with a full complement of harmonics, including a high order (22kHz) harmonic that's 100-10,000 times lower in level than the (110dB) fundamental and many times lower than the other harmonics, what do you think would happen? First of all, we couldn't even run that test, it would be too uncomfortable/painful, we'd have to lower the level by around ten times! But even if we could, we already know no one has ever demonstrated the ability to hear even a pure 22kHz tone at only 70dB (let alone at 30dB) but in the presence of a far higher level fundamental and set of harmonics, it would be like asking Usain Bolt to run 100m in 9.58 seconds, in a sack race! Do we not have something we can treat as a certainty here? And let's not forget, this isn't just theory, I and countless other engineers have tested this.



Why, what's the point, when we already know "what it is" and have done for at least 6 decades?

G

 

[bigshot]

Thanks for the link to that article. Very interesting. It basically justified the belief I already held.

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

 

[gregorio]

[1] The fastest human runner in 1860 could run a mile in about 4:45. Today the fastest runner can do it in just under 3:43
[2] The land speed record for wheeled vehicles is 7.5x as fast today as the record in 1905.
[3] And we now know that the lower frequency limit for hearing is 12 Hz and not the previously believed 20 Hz.
(And that's presumably just due to limits or errors in previous experiments.)
[4] Considering that 30 kHz is only 50% above 20 kHz...
[5] And we already know that some people can hear beyond 20 kHz...
[6] It just doesn't seem especially unlikely to me.
[7] I just can't figure out how some other people can be so absolutely positively sure...

1. There's no evidence to suggest that training can increase hearing freq response (as it clearly does with athletics).
2. Are you a wheeled vehicle?
3. We don't "know" that and ascertaining low freq response is a completely different issue to ultrasonic response.
4. Only 50%, maybe it will only take us a million years to evolve only a 50% increase?
5. No, there is no evidence that people can hear beyond 20kHz with musical content, plenty against though.
6. Without any evidence, what seems especially unlikely to you is not relevant to this thread or this forum.
7. Firstly, a lack of evidence despite decades of looking for some. Secondly, tons of evidence against and Lastly, the range of adult hearing and the levels of ultrasonic content in music makes it illogical that it could be audible, unless we've got something fundamentally wrong with our understanding of hearing and again, there's no evidence of that. I can't figure out how some people aren't sure!

G