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Do sounds outside our hearing spectrum affect perceived sounds within the range?

 
 
uppsju
 
Reply Wed 21 Dec, 2011 07:58 am
On wikipedia and elsewhere I've read that the human hearing range lies between 20Hz - 20kHz, with some variation between individuals. I make an assumption that when you're listening to someone playing a guitar for example, the guitar will generate sounds both within and outside our hearing range.
My question is: if you make a recording of the guitar being played, one that includes frequencies let's say up to 26kHz, and another one which only goes as far as 20kHz, will we be able to detect a difference? In other words, can the "unheard" frequencies still have an effect on how we perceive the sounds of the guitar within the hearing range?
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Type: Question • Score: 9 • Views: 3,995 • Replies: 21
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Joe Nation
 
  1  
Reply Wed 21 Dec, 2011 08:44 am
This is a great question and one that I haven't much informed knowledge to help in answering.
I will say that at some musical concerts I have felt the deepest bass notes on my chest.
Joe(as well as some of the amplified drumbeats)Nation
0 Replies
 
Ragman
 
  2  
Reply Wed 21 Dec, 2011 08:53 am
@uppsju,
[Edit: My orig thoughts]

Musical overtones and harmonics are theoretically possible to be recorded and reproduced from speakers but they've little effect as it's outside the human threshhold of sensual perception. The fact that electronics might reproduce it is ALMOST a moot point.

You can prove this with play back or recording the tones and then notch filter out completely any tones after 20khz. When you listen to the result, you won't perceive any difference.

Also if you have access to some test equip't, grab a tone generator and a oscilliscope. Generate a tone beyond 20 khz. Using an o-scope, set a freq with an amplitude that matches the amplitude of the other notes in the music. Listen to the result in the music with and without the high freqs. I will bet you will not here any difference.

After the age of 40 males (particularly those who lived near cities) generally start to lose the high end tones...as they can't hear much beyond 18-19 khz, never mind the top frequencies of 20 khz. Urban noises and listening to concert level of rock music at loud volumes tend to destroy the high end even at the 15 khz band.

However, it is quite a bit different in the case of low bass. Your body and skeletons do react to low frequencies..even if not heard. Bones, muscles, stomach, chest and intestines react to deep bass - especially at loud volumes. In fact, loud subsonic bass generators has been used as weaponry in warfare as it can cause loss of control of the bowels.

[Edit: revised]

Evidence of what proves the mprveious might be wrong relates to the religious debate over vinyl lovers vs CD lovers. Vinyl versions of the same music recorded similarly will show that the vinyl versions are warmer sounding and more inviting to listen to.

Digital recordings on CD often use a brick-filter (notching out of the harmonics after 20 khz). They often sound cold or clinical sounding. I've proven the diffference to myself and others with Dire Straits 'Brother in Arms' recording on CD and with vinyl. Both sound good, but vinyl is better. Part of this relates directly to the present overtones or harmonics in the recording and reproduction of the overtones or harmonics using the right high fidelity quality speaker.
Ragman
 
  1  
Reply Wed 21 Dec, 2011 09:12 am
@Ragman,
Ragman wrote:

[Edit: My orig thoughts]

You can prove this with play back or recording the tones and then notch filter out completely any tones after 20khz. When you listen to the result, you won't perceive any difference.


That should have read, "you might not perceive the difference as it does require close listening. If the music is crowded with a lot of notes at once, the difference will be very tough to perceive.
0 Replies
 
Ragman
 
  1  
Reply Wed 21 Dec, 2011 09:15 am
@Ragman,
This phrase that describes this topic is called psycho-acoustics. Google the phrase to see some amazing discussions.

When talking electric guitar, the most iportant region of harmonics for characterizing the timbre is around 1.5kHz to 8kHz (fundamentals to first order of harmonics). This is why guitar tones from speakers show an interesting variation in frequency response over this range (in general a boost between 2-4k and a slight cut at 3k).

The harmonics which occur higher than this have meaningful implications when combined in different ways effecting 'brightness' or 'airyness' but do not affect the signature voice of the speakers reproduction.

"So that means my electric guitar has tones going to several thousand Hz when playing clean.

However, when I add distortion, even slight overdrive, the spectrum is very complex. With hard distortion the harmonics go past 20kHz. Another reason old vinyl recordings of classic rock (as well as everything else) sound so much better than the bandwidth reduced CD.

So to conclude, at least for electric guitar, the frequency spectrum is very wide indeed."
patiodog
 
  2  
Reply Wed 21 Dec, 2011 10:14 am
@Ragman,
Great question.

Not sure I'm sold on the notion that reproduction of ultrasonic overtones is the reason that analog recording and reproduction sounds "warmer" than when digital is introduced into the mix. Just because analog is theoretically capable of reproducing frequencies over 20 kHz doesn't mean that we somehow perceive them directly. I would think it's at least equally possible that the quantization of digital recording -- chopping up the continuous stream of sound into very short bits -- affects the texture of the final product.

What I really suspect, though, is that there's just something about the "dirt" in the sound of an LP playing that we find inherently pleasing.

Without a doubt, though, ultrasonic frequencies affect the character of the sound that we are able to hear. When tones are produced by a stringed instrument or reproduced through an amplifier, all of the tones together combine to produce a single complex waveform.

This site, judging from a brief skim, looks to cover the effects of constructive and destructive interference between sound waves pretty well: http://www.physicsclassroom.com/class/sound/u11l3a.cfm

This image from the site illustrates how "pure" tones an octave apart (the higher note having a frequency exactly double that of the lower note) interact to create a waveform with periodically increasing and decreasing amplitude.

http://www.physicsclassroom.com/class/sound/u11l3a2.gif

These amplitude shifts are called beats, and for complex combinations of notes -- or even a single note and multiple orders of overtones from an instrument -- beats created by interference caused by higher frequency tones are generated at considerably lower frequencies. So, it is very likely that tones with frequencies outside the range our ears actually can detect are affecting the texture of the overall tone in ways that are perceptible, if subtle.

Maybe, though, analog recording and reproduction are better able to reproduce these subtleties than digital recording. Even within the analog realm, tube amplification produces what's generally accepted to be a warmer tone than solid-state amplification, though I've never seen a scientific explanation of how the different signal paths produce quantitatively different signals.

Come to think of it, I've never looked for one. I think I'll do that for a bit now...

(Keeping in mind that the tube vs. solid state argument is generally to do with the quality of the distortion -- but since distortion always emphasizes and generates certain high frequency overtones or additive noise, I think the question is relevant to the question of perception of sound...)
patiodog
 
  1  
Reply Wed 21 Dec, 2011 10:37 am
@patiodog,
Not quickly finding anything that addresses my wondering directly, and realizing I'm in danger of wasting a large chunk of a day that I meant to be productive, giving up the search.

A quick glance at a discussion of generation of resonance by the sound board and body cavity of an acoustic guitar sparks a huinch about tube distortion -- however tangential it may actually be to the topic...

A tube may be mechanically better able to provide its own resonance mechanically -- because its filament can vibrate -- than a solid-state transistor, which as far as I know has no parts capable of movement. This quality would be a detriment in faithful reproduction of sound in power amplification (which tube amps are quite bad at) but would be a boon for generating its own characteristic tone, particularly when overdriven...
Ragman
 
  1  
Reply Wed 21 Dec, 2011 10:40 am
@patiodog,
Perhaps further discussion should occur of some of the the process of making CDs in the recording as well as the reproduction of sound through CD players?.In the process of recording a CD (vs recording alalogue) there is a filtering that occurs of frequencies beyond 20 khz.

Also, built into CD players is a 'brick-wall' filter that virtually elimnates anything over 20 khz. This filtering has a psycho-acoustic effect of removing of warmth..some call it clinical sounding. Upper end hi-fi CD mfrs have done some wave-shaping to make the effect lessened.

However, some of the subtle nuances from this reduction in sampling rate resolution due to the arbitrary sampling rate removes a presence that gives the brain the sense of life and naturalness as compared to analogue recording/reproduction.

Furthermore, in the psycho-acoustic issue.... is that digital recording and reproduction is that there's a finite sampling rate that breaks the signal intio discrete steps. See the following about sampling rate:

http://en.wikipedia.org/wiki/Sampling_rate

"The full range of human hearing is between 20 Hz and 20 kHz.[3] The minimum sampling rate that satisfies the sampling theorem for this full bandwidth is 40 kHz. The 44.1 kHz sampling rate used for Compact Disc was chosen for this and other technical reasons.

[edit] Oversampling

... "


This breaking up into discrete staircase steps (as seen on an o-scope) creates a certain resolution. The human ear perceives this as a coherent integrated sound. However psycho-acoustically when we hear analogue (as comparwed to CD) as reproduced on a vinyl lp, we often times sense an inviting warmth -- or as a non-brittle non-clinic sound.

Don't take my word for it. Compare for yourself the same music on a CD vs vinyl as I've done over the last 25 yrs. There is a differences in that one area of psycho-acoustics.
0 Replies
 
Ragman
 
  1  
Reply Wed 21 Dec, 2011 10:44 am
@patiodog,
Yes, I too wanted to avoid the tube vs transistor debate. It is interesting but can take these tangential to the discussiion. The microphonics of the filaments in the tube plus its mysterious inherent warmth from the "bottle sound" are always the darling of guitaristas and the analogue lovers of the audiophile world.

FWIW, my separate primary preamp is tube and so is my preamp for turntable.
0 Replies
 
Ragman
 
  1  
Reply Wed 21 Dec, 2011 11:03 am
@patiodog,
I'm not doing the whole complex topic justice. But there is something further to be understood about presence of odd and even harmonics that this discussion of psycho-acoustics should include. Sadly, I'm not qualified to do this. What I do know that the presence of odd harmonics in digital repro is one of the artifacts that makes them less pleasing psycho-acoustically.

"What can make reproduced sound shrill & fatiguing because of the odd harmonics that it produces. And to impart the even harmonics back into the mix requires analog gear in the signal path at mix down such as a summing device/console."
patiodog
 
  1  
Reply Wed 21 Dec, 2011 01:07 pm
@Ragman,
ragman wrote:
Also, built into CD players is a 'brick-wall' filter that virtually elimnates anything over 20 khz. This filtering has a psycho-acoustic effect of removing of warmth..some call it clinical sounding. Upper end hi-fi CD mfrs have done some wave-shaping to make the effect lessened.


Yeah, I get this. Intuitively, it doesn't entirely add up to me that this would be perceptible to us as long as the effects ofthe ultrasonic harmonics on the underlying waveform are preserved. But I'm probably wrong, or the underlying waveform is altered by the filter as well -- especially if manufacturers are spending money to counter the effect.

(Or perhaps the higher frequencies have to be intact for the speaker to faithfully reproduce the waveform? Way out of my depth, of course...)

Interesting experiment would be to put such a filter in an anolog signal path and see if you can hear the difference when you roll off everything over 20 kHz. I certainly don't have an EQ in the house that can do that, though.

Quote:
However, some of the subtle nuances from this reduction in sampling rate resolution due to the arbitrary sampling rate removes a presence that gives the brain the sense of life and naturalness as compared to analogue recording/reproduction.


Yeah, this is what I mean by quantization --> turning a continuous phenomenon, a sound wave, into a series of discrete phenomena.


Quote:
But there is something further to be understood about presence of odd and even harmonics that this discussion of psycho-acoustics should include. Sadly, I'm not qualified to do this. What I do know that the presence of odd harmonics in digital repro is one of the artifacts that makes them less pleasing psycho-acoustically.

"What can make reproduced sound shrill & fatiguing because of the odd harmonics that it produces. And to impart the even harmonics back into the mix requires analog gear in the signal path at mix down such as a summing device/console."


Now this makes a lot of sense to me. Probably why I find even a digitally-simulated distortion so much more pleasing (though not necessarily preferable) on a neck pickup than the bridge...

patiodog
 
  1  
Reply Wed 21 Dec, 2011 01:11 pm
@patiodog,
Actually, just now realizing I'm being stupid and not considering what a filter actually does to the signal. I think I get it now. Duh...
Ragman
 
  1  
Reply Wed 21 Dec, 2011 02:42 pm
@patiodog,
What's a neck pickup? I've seen plenty of bridge pickups but didn't know they had them for the neck.

Looking it up I found the following:

"The Fender Telecaster features two single coils. The neck pickup produces a mellower sound, while the bridge pickup produces an extremely twangy, sharp tone with exaggerated treble response, because the bridge pickup is mounted on a steel plate. These design elements allow musicians to emulate steel guitar sounds, making it particularly appropriate for country music.

Pickups are selected with a three-position switch, and two wiring schemes exist:
Vintage: 1) neck pickup with treble cutoff for a bassier sound; 2) neck pickup only; 3) bridge pickup only.
Modern: 1) neck pickup only, with no treble cutoff; 2) neck and bridge; 3) bridge pickup only.

The Fender Esquire has a variation to the Vintage wiring scheme by using the scheme on a single pickup. This gives a treble cutoff in the first position, normal in the middle position, and a tone control cutoff in the third position."


Ok..back to filtering...
... And the problem with brick-wall filtering on DACs in CD players and what not is that the evil lies in how it slams the door instead of rolling it off more gradually or pleasingly.

I find it fun to chat about this stuff. Seems that you do, too. wonder if we're the only 2 that do?

Now to put on a 40-yr-old vinyl on my turntable and fire up the tube preamps.
roger
 
  1  
Reply Wed 21 Dec, 2011 03:22 pm
@patiodog,
My goodness, but you and Rags sound knowledgeable, so let me try another question on you.

My hearing is seriously impared, and here's an interesting side of that. I hear quite well over a conventional telephone and with headphones on an MP3 player. Other electronicly produced sounds, like television and the speakers in theaters give me nothing but noise.

Does this relate to the discussion? If not, I'm interested in any random comments.
patiodog
 
  1  
Reply Wed 21 Dec, 2011 03:29 pm
@Ragman,
Quote:
What's a neck pickup? I've seen plenty of bridge pickups but didn't know they had them for the neck.


Most simply, it's the pickup furthest from the bridge pickup, closest to where the neck mounts onto the body of the guitar. It seems to me to pick up more of the tone of the note and the one- and two-octave overtones for open strings, whereas the bridge pickup gets more of the odd harmonics and the string noise (pick attack, finger slides). Of course, guitars like the Strat also have a middle pickup, but the only guitars I've got around the house just sport paired humbuckers. The old Hofner guitars describe the difference as "bass" for the neck pickup and "treble" for the bridge pickup, but this seems to be a gross oversimplification to me.

Quote:
... And the problem with brick-wall filtering on DACs in CD players and what not is that the evil lies in how it slams the door instead of rolling it off more gradually or pleasingly.


So is there a technical reason, do you think, that they wouldn't use a roll-off filter? In my distant memories of sound reinforcement, about the only use for a shelf filter like that is to get rid of unwanted noise somewhere in the signal chain, unless you're using it in phasing or flanging effect...

Quote:
I find it fun to chat about this stuff. Seems that you do, too. wonder if we're the only 2 that do?


It's possible. Truth be told, I'm not much of an audiophile, but the technical challenges interest me, and since all my gear is cheap or cheapish, it can be useful to know just how it's compromised...

(Frankly, I love the tone of my solid-state Fender Bassman 150 --- but you certainly can't drive the thing usefully, and I suspect the tinge of warmth I like about it comes from the speaker and not the amp.)

Yeah, OK, back to painting. Really.
0 Replies
 
patiodog
 
  1  
Reply Wed 21 Dec, 2011 03:37 pm
@roger,
Quote:
My hearing is seriously impared, and here's an interesting side of that. I hear quite well over a conventional telephone and with headphones on an MP3 player. Other electronicly produced sounds, like television and the speakers in theaters give me nothing but noise.


Just a guess, but I'd hazard that the devices you hear well -- phone, small headphones -- are usually very focused on reproducing midrange tones, which the ear handles very well and where hearing doesn't tend to be lost as readily as higher frequencies. Certainly movie theaters and large stereo speakers and possibly speakers in a TV are more likely to be producing sound with a "scooped" profile: high and low frequencies are emphasized, leaving the midrange relatively scooped out. We tend to experience scooped sounds as having more depth or being more spacious. If most of your hearing loss is above, say, 10 kHz, you're going to be hearing a pretty muddy sound overall.
roger
 
  1  
Reply Wed 21 Dec, 2011 03:43 pm
@patiodog,
Well, high frequencies are pretty well gone in both ears, and muddy is an understated but accurate description.
0 Replies
 
Ragman
 
  1  
Reply Wed 21 Dec, 2011 04:41 pm
@patiodog,
I agree re that sort of hearing loss. Mid freqs (voices, singers and dialogue) is emphasized but a dull roar is heard for highs.

People that have worked near heavy machinery or around rifle ranges or in combat ...have losses from 8khz upward.
0 Replies
 
Eorl
 
  1  
Reply Wed 21 Dec, 2011 06:31 pm
It's complicated. Just because you can't hear frequencies outside the audible range doesn't mean the presence of such frequencies won't effect what you are hearing. For example, if you add a 10hz tone and a 30hz tone to a speaker that is playing music, you'll hear a difference for a couple of reasons. The lower tone (and to some extent the high one) will produce harmonics in the audible spectrum, and the higher tone will have your speaker very busy, altering it's abililty to produce the other sounds.
hingehead
 
  1  
Reply Wed 21 Dec, 2011 07:16 pm
Add to Eorl's complication that sub and hypersonic sound can affect your physiology, conceivably affecting your perception of audible sound - without affecting the sound itself. Pretty cool question.
0 Replies
 
 

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