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Can you trust your ears? Yes and no ....

HUG-1

Moderator
Definitions:

Psychology - the study of normal human behaviour
Acoustics - the study of sound

hence,

Psychoacoustics - the study of normal human behaviour in response the presence of an external sound stimulus
[HR][/HR]
Those professionals who make a living studying psychoacoustics have 100 years of observation and experimental research to draw upon. Psychoacoustics is a very mature science, and there have been no new discoveries, nor are there likely to be, that have cast doubt on the accrued academic legacy. The commercialisation of that knowledge surrounds us, from the implementation of FM radio, vinyl records, Dolby, the CD audio concept, MP3, AAC, mobile telephony, multi-channel sound at home and in the cinema and audio streaming. All are possible because the operation of the human ear is thoroughly understood, and there are no gaps in the foundation knowledge. Those, like Dolby Labs and Fraunhofer Institute have made a fortune from watertight patents on audio data reduction (AAC, MP3) that are not contestable or circumventable because the psychoacoustics that underpins them is factual, and demonstrable. 'He who understands the ear and works with it can make money from it'.

One fundamental observation by psychoacousticians is that the mechanical-chemical-electrical system that we call the ear is vulnerable to disease, exposure and ageing. There are over 200 medical conditions known to be associated with an effect on the ear, and numerous pharmaceutical products have side effects which impact on hearing. Age, has a tremendous degrading effect, and it is inconceivable that anyone in middle years has the hearing of a ten year old, when the ear's performance is at a maxima. It's downhill all the way from then on hopefully in a shallow, but straight line gradient.

One observation that is beginners-grade fundamental to psychoacoustics -

The ear detects sound by movement of mechanical parts within the ear (video here). Because our human bodies must be sealed from the atmosphere or we would leak out into the environment, the sound waves that hit our ears cannot be directly allowed to directly enter our bodies. We must transfer the pressure waves of those external sounds into motion internal to our bodies before we can decode them. We do this using a mechanical transfomer, a sort of rope and pulley system involving the three smallest bones in the body in what we call the middle ear. So before the sound even reached the hair cell sensors where it is converted to electrical energy, it is already a mechanical-motion reintrpretation of the external sound world, with all the limitations that any reinterpretation imposes.

The operation of the inner ear converts that first step transformation to a secondary transformation. The result is that to one degree of precision or another (depending upon innumerable variables), a sloshing liquid wave is made to that travel in the sealed inner ear in approximate sympathy to the external sound wave. That fluid motion causes tiny hair cells to bend like trees in the wind and their flexing generates a pulse, which is fed to the brain. So the ear is not 'analogue', it is digital. Nerves are fired according to the fluid motion, and those nerves have two states: on, or off.

Second: the only way the ear can detect the extrenal world is through motion of the eaer drum. Because the movement of that diaphragm is so tiny, it should be expected that only proportion of the external sound is transfered to and through the three bones of the inner ear to reach the oval window. This is by evolutionary design whereby the inner hair sensors are optimally 'geared' to a specific range of loudness. It also follows that, as with all mechanical systems, there are friction losses, usually as heat. It is also the case that the bone-on-bone sliding operation of the inner ear - see video above - is not 100% efficient, as no mechanical coupling can be. When the sound energy is high, the losses are negligible but when the sound energy drops, those losses become significant. When the external sound is very quiet, the bones are not given enough motion energy to move, and hence no sound wave is sent on to the hair cells. That defines the minimum threshold of hearing.

What that means is this -

Considering the inevitable inefficiencies in the coupling mechanism of the external sound wave to the sound sensors deep in the inner ear, the exact loudness that we listen to and judge sound is all critical in how we interpret that sound. We cannot ever 'hear true sound'. What is passed to our brains is a third hand version of the pressure waves we call sound in the external world, after two transformations in the ear.

So what?

Any reliable, repeatable and universally accepted subjective comments relating the performance of any, all and every piece of sound generating equipment, or of music live or reproduced, is only even approximately valid if steps are taken to investigate, ascertain and fix how loud that sound wave was at the listener's ear. Even then, there will be small, person to person differences due to the structure of the ear, the losses and inefficiencies of the transcoding process which will alter the subjective impresion in the brain. But they are of secondary importance.

Call to action -

It is folly to believe that a truly objective, scientific selection of audio equipment can be made by uncontrolled, casual listening appraisal. The nature of the ears perception of small changes in loudness, very well documented, read here, means that comments like "I've just listened to amp A and it blows away amp B for dynamics and resolution" are not only worthless as objective appraisal, but almost certainly could be reversed under conditions where the louder of the two equipments, A, is adjusted to be the quieter, with the result that the observer would now, with equal conviction, report "I've just listened to amp B and it blows away amp A for dynamics and resolution".

NOTE! The simplest, cheapest and most assured way for an audio equipment maker to swing the would-be consumer (or reviewer's) preference towards his product and away from the competition is to make is slightly LOUDER! The resulting preference is absolutely inevitable.

So, when we receive comments about dramatic differences between electronics, to protect our stance over the relatively insignificant performance variations between modern electronics and to weed-out product-placement endorsements, we will expect to read what steps have been taken to equalise loudness during the comparison or the post will not pass moderation. Loudness difference is that influential.
 

A.S.

Administrator
Staff member
Volume control - absolutely VITAL

Volume control - absolutely VITAL

...
What that means is this -

Considering the inevitable inefficiencies in the coupling mechanism of the external sound wave to the sound sensors deep in the inner ear, the exact loudness that we listen to and judge sound is all critical in how we interpret that sound. We cannot ever 'hear true sound'. What is passed to our brains is a third hand version of the pressure waves we call sound in the external world, after two transformations in the ear.

So what?

Any reliable, repeatable and universally accepted subjective comments relating the performance of any, all and every piece of sound generating equipment, or of music live or reproduced, is only even approximately valid if steps are taken to investigate, ascertain and fix how loud that sound wave was at the listener's ear. Even then, there will be small, person to person differences due to the structure of the ear, the losses and inefficiencies of the transcoding process which will alter the subjective impression in the brain. But they are of secondary importance.

Call to action -

It is folly to believe that a truly objective, scientific selection of audio equipment can be made by uncontrolled, casual listening appraisal. The nature of the ears perception of small changes in loudness, very well documented, read here, means that comments like "I've just listened to amp A and it blows away amp B for dynamics and resolution" are not only worthless as objective appraisal, but almost certainly could be reversed under conditions where the louder of the two equipments, A, is adjusted to be the quieter, with the result that the observer would now, with equal conviction, report "I've just listened to amp B and it blows away amp A for dynamics and resolution".

NOTE! The simplest, cheapest and most assured way for an audio equipment maker to swing the would-be consumer (or reviewer's) preference towards his product and away from the competition is to make is slightly LOUDER! The resulting preference is absolutely inevitable.

So, when we receive comments about dramatic differences between electronics, to protect our stance over the relatively insignificant performance variations between modern electronics and to weed-out product-placement endorsements, we will expect to read what steps have been taken to equalise loudness during the comparison or the post will not pass moderation. Loudness difference is that influential.
Although I have been making this comment about the critical importance of loudness control when judging audio equipment, and have mentioned the sort of level matching I have myself discovered is essential and reported here being essential to remove the subjective preferential bias, here is a video from a top recording engineer quoting exactly the same level mismatch, and the subjective impression it deceived him into.

Note how the audience of Audio Engineering Society industry professionals react, knowingly, when he explains this point. Everyone on the inside of the industry 'gets it' about level match, and has 'got it' for about a century. The audiophile does not want to 'get it' so makes the wrong equipment purchases.

Video here.

More on mastering and loudness in the studio here
 

pkwba

New member
Audio industry veteran's short lecture on loudness.

Audio industry veteran's short lecture on loudness.

Although I have been making this comment about th4e critical importance of loudness control when judging audio equipment, and have mentioned the sort of level matching I have found and reported here, by my own experimentation, is essential to remove the subjective bias, here is a video from a tom recording engineer quoting exactly the same level mismatch, and the subjective impression it deceived him into.
Exactly, watch also "Bob Katz - Loudness: War & Peace" - link https://www.youtube.com/watch?v=u9Fb3rWNWDA. What struck me is the fact that sound engineer has no voice while mastering pop - musicians and their company advisors decide about quality of the final sound! Half deaf from stage performing with loudhailer equipment individuals decide about studio sound, incredible! Notice that this prominent audio engineer does not identify himself with those marketing practices, client is always right (contrary - he says "my classical and jazz recordings"), the bussiness must run .....

I wonder how succesfull would be the professional career of eg. Rudy van Gelder or Tom Dowd in today recording industry?
 

anonymous

New member
"Loudness trumps sound quality."

"Loudness trumps sound quality."

Although I have been making this comment about the critical importance of loudness control when judging audio equipment, and have mentioned the sort of level matching I have myself discovered is essential and reported here being essential to remove the subjective preferential bias, here is a video from a top recording engineer quoting exactly the same level mismatch, and the subjective impression it deceived him into.

Note how the audience of Audio Engineering Society industry professionals react, knowingly, when he explains this point. Everyone on the inside of the industry 'gets it' about level match, and has 'got it' for about a century. The audiophile does not want to 'get it' so makes the wrong equipment purchases.
"Loudness trumps sound quality." Even if it's as little as 1 dB. An increase of 4, 5, or 6 dB in the whole history of analog, but over 20 years of the compact disc there was a 20 dB increase in the average level. That's amazing. It goes to show that there are a lot of industry professionals addicted to loudness.

The Audio Engineering Society (a professional body) has their work cut out for them. I came across this paper, which I have yet to fully read but skimmed through. Irrespective of the author's comments about content, the paper he references sounds interesting, from page 19:

A recent and important study examined the effects of radio sound processing on listener’s program choices. Maempel and Gawlik tested 60 non-expert subjects using various music pieces and one speech recording, processed with a variety of typical radio processing settings that varied in loudness and crest factor. One experiment performed a conventional test whereby the subjects could directly compare different types of processing using the same source material; in this test, as expected, there was a distinct preference for specific processing types, with an apparent advantage for high loudness and high bass.
 

A.S.

Administrator
Staff member
Do we really understand "loudness" defines EVERYTHING in audio?

Do we really understand "loudness" defines EVERYTHING in audio?

"Loudness trumps sound quality."... I came across this paper, which I have yet to fully read but skimmed through. Irrespective of the author's comments about content, the paper he references sounds interesting, from page 19:
That's a really interesting paper. We need to look at that in more detail.

What strikes me yet again is that some of us have been harping on about the loudness of audio, both of audio equipment and recordings themselves, for many years. We on this side of the desk not only hear and recognise the sonic nature of increasing loudness as perceived by the ear and measured with technical equipment, but we also know that commercial motives that would (and do) drive the production process that brings hifi equipment and recorded music to our homes. We, on this side, know and have frequently cautioned that loudness - simple loudness - drives the sales process and that if a recording or piece of equipment is louder, it will sell better than one that has an identical specification, but is slightly quieter.

So what would the canny marketeer do, to take maximum advantage of this dirty little trick? He'd up the loudness of his equipment/recording so that it caught the casual listener. That's exactly what has being going on for a couple of decades. Unfortunately, in a competitive environment, the competition similarly respond, so year by year, loudness is racked-up across the industry. Amplifier volume control have been adjusted so that they no longer offer progressive volume increments across the whole rotary sweep, they bunch-up the colume towards the bottom of the scale to give the illusion of greater power. Record companies compress then increase the loudness of recordings until they bear no relationship with the source master tape.

Do we all, without reservation or doubt, accept that the only way a human can detect sound is by its loudness at any given frequency, and if that loudness is manipulated, our personal sensory experience will also be revised? If we do accept that, it follows that to make so-called 'comparisons' of audio equipment in the absence of controlling (or even measuring) the replay loudness at the listener's ear is madness. There can be no other conclusion.

It follows that if no attempt is made to regulate loudness so that item A is listened to at the same loudness as item B, then the listener might as well flip a coin when making a selection, because if loudness is not exactly comparable (within a tiny fraction of a decibel) he is not discovering some latent magic in the equipment but commenting on his own ear's mechanical operation.

As stated here.

Any problem with that?

Another example of how to do a fair comparison, after loudness level matching here
 
S

stevieshep

Guest
Bionic earrs and loudness criticality

Bionic earrs and loudness criticality

Yes Alan, I understand exactly what you are saying only too well, it is something I have very personally experienced and understand deeply. Having suffered from Otosclorosis for many, many years, the effects of which are a reduction in loudness and in turn noise and sound perception, this comes about by a reduction in movement of the 3 bones in the middle ear. Unfortunately mine got to an extreme stage of severe hearing loss in both ears so I have experienced that side and how loudness and sound perception are linked.

I no longer have 3 small bones in each ear, I have 2 bones and one flouroplastic piston in each, no stapes bones left now!!, so does that make my ears bionic??, in that case I must be superior to anyone with golden ears!!

The stapadectomy operation on each ear was without doubt the best upgrade I ever purchased and I now have normal hearing in both ears( for a 48 year old anyway).
Having experienced this disease and it's impact means I fully understand and comprehend your point Alan, and it's absolutely correct, readers you can take my word for it also.

I have a totally different perspective of sound now to prior to my operation and the effect loudness has to my reaction and perception of sound and indeed enjoyment. It is as if the volume has been turned up and all of a sudden all the quiet background noises and sounds I couldn't hear before are new to me, a bit like that great new amp that the reviewer has raved about in the latest hifi mag!!.

YES LOUDNESS IS CRITICAL TO HEARING PERCEPTION.
 

A.S.

Administrator
Staff member
Brass test

Brass test

Yes Alan, I understand exactly what you are saying only too well, it is something I have very personally experienced and understand deeply. Having suffered from Otosclorosis for many, many years... I have a totally different perspective of sound now to prior to my operation and the effect loudness has to my reaction and perception of sound and indeed enjoyment. It is as if the volume has been turned up and all of a sudden all the quiet background noises and sounds I couldn't hear before are new to me, a bit like that great new amp that the reviewer has raved about in the latest hifi mag!!.

YES LOUDNESS IS CRITICAL TO HEARING PERCEPTION.
That's a fascinating read. I had no idea that operations of that complexity could be undertaken in the middle ear. You are very brave. May I ask, how did they gain access to the three bones of the middle ear?

I was just playing around with an idea of demonstrating the subjective influence of an objective (real, measurable) change in loudness. I made this little clip. It is the same music three times in the sequence A, B, A. Now, what struck me on playback is that in A, the orchestra sound normally balanced, but in B, the brass takes on a sharper, rasping, slightly uncomfortable and irritating, disembodied sound that doesn't seem to be integrated with the full orchestra and massed voices properly: it sounds somewhat artificial.

Anyone else have that sensation, or equally valid, any other sensation contrasting A with B?

 

pkwba

New member
Furtwangler for gangsta.

Furtwangler for gangsta.

"One of Abbey Road Studios' most experienced mastering engineers, Simon Gibson, talks us through the process of remastering Furtwangler". - Abbey Road Studios

Link to this extremely interesting presentation of technical miracles "modern" engineers can do to the old recordings in the worldwide renowned studio - https://www.youtube.com/watch?v=PfA61_noOQQ

I warmly invite to watch all this video but especially steadily in the section 5:55 to 8:15.

My doubts are:

1. Is anybody, even the most experienced mastering engineer, entitled to change (expand) the dynamic range of the original (flat) digital copy from master tape?

2. Is such an "expanded" (if it is truly expanded, maybe elevated?) sound better or more natural sound of an orchestra?

3. Is the basic idea of "high resolution" carriers (sacd, dvd-audio, blu-ray audio, hi-res files) to bring to listener the hypernatural audio dynamics or to embrace as much as possible whole the natural description of recorded, sometimes very complex, sound?

Maybe my questions are irrational and I am dilettante, all in all I am music lover only ....
The longer adhesion to HUG, the more previously non risen thoughts and consternations about all this audio mess I have ...:)
 

anonymous

New member
Accepting our ears

Accepting our ears

Do we all, without reservation or doubt, accept that the only way a human can detect sound is by its loudness at any given frequency, and if that loudness is manipulated, our personal sensory experience will also be revised? If we do accept that, it follows that to make so-called 'comparisons' of audio equipment in the absence of controlling (or even measuring) the replay loudness at the listener's ear is madness. There can be no other conclusion.

It follows that if no attempt is made to regulate loudness so that item A is listened to at the same loudness as item B, then the listener might as well flip a coin when making a selection, because if loudness is not exactly comparable (within a tiny fraction of a decibel) he is not discovering some latent magic in the equipment but commenting on his own ear's mechanical operation.

As stated here.

Any problem with that?
I accept this without reservation. Learning about this in the past year or two has made my subscriptions to two audiophile periodicals and reading gear comparisons on forums even more unendurable.

I came across this recently. It gives some idea of the pains those who are serious about comparisons go to:

METHODS FOR THE SUBJECTIVE ASSESSMENT OF SMALL IMPAIRMENTS IN AUDIO SYSTEMS INCLUDING MULTICHANNEL SOUND SYSTEMS

It also touches on the issue of aural memory.
 
S

stevieshep

Guest
Prof. Marcus Altas

Prof. Marcus Altas

Hi Alan,

No it wasn't brave really, i was faced with no other choice, I suppose that might sound blase, I was extremely nervous and anxious but I had a fantastic surgeon with an excellent reputation and track record, his name is Professor Marcus Atlas and fortunately he lives here in Western Australia.

The surgery is micro with laser, he makes a small incision down the ear canal but does not touch the ear drum, extremely clever. I am very grateful to Prof. Atlas. The restoration of my hearing has been a life changing experience, you cannot imagine just how good my SHL5s sound to me, they were my present to myself after my ears were restored.
 

A.S.

Administrator
Staff member
Prof. Altus

Prof. Altus

No it wasn't brave really, i was faced with no other choice, I suppose that might sound blase, I was extremely nervous and anxious but I had a fantastic surgeon with an excellent reputation and track record, his name is Professor Marcus Atlas and fortunately he lives here in Western Australia.

The surgery is micro with laser, he makes a small incision down the ear canal but does not touch the ear drum, extremely clever. I am very grateful to Prof. Atlas. The restoration of my hearing has been a life changing experience, you cannot imagine just how good my SHL5s sound to me, they were my present to myself after my ears were restored.
That really is an astonishing experience. I found information on Prof. Altas here.

It is a source of great regret that those, like the Professor, who know more about the workings of the ear than the entire audiophile community combined, clearly do not spend their time on audio forums trying to reason with those who have an irrational and unshakable faith in their ears. If you do not have at least a rudimentary understanding of the ear, you should not be allowed to spout audiophile propaganda: I'm sure he would agree with that.

Please do keep us posted on this very interesting are of Otolaryngology.
 
S

stevieshep

Guest
Otosclorosis and progressive hearing loss

Otosclorosis and progressive hearing loss

Please bear in mind that I am not medically qualified, this only my personal experience and accumulated knowledge. I suppose I, like many others was ignorant to the ear and how it operates. I learned about my ears because of the disease I had, Otosclorosis. Very little is known about the cause of this disease, indeed the 2 stapes bones from my ears were kept for research purposes, I did ask to keep them for souvenirs!!. They are very small bones, a few millimetres only.

The disease can vary from person to person in severity and it can affect one only or both ears. I suspect there may be many people who have this but it is mistaken for normal hearing loss and perhaps does not get diagnosed.

The hearing tests I had, used for diagnosis and post operative are very thorough, consisting of the usual tone tests in each ear and also through the skull bone. To compliment these I also had to listen to softly spoken words that are easily mistaken or misunderstood and repeat them, they are spoken into each ear with headphones. On top of this a type of wind noise of different frequency and volume is played into each ear whilst the tones are played into the other, this is something that sufferers of Otosclorosis find particularly hard to do.

The onset of the disease is very, very gradual, it takes years to develop, certainly in my case (18 years). Because of this slow development the brain adapts and I didn't realise for a very long time that there was a problem, then I just assumed it was workplace related hearing loss. But the hearing loss just got worse and worse, I ended up with severe hearing loss and was close to being deaf. The world was a very quiet peaceful place!!. Hearing aids were no longer any help (I hated them anyway). I could no longer enjoy music. So in the end I had no choice, being deaf was not an option for me. I had to have a 12 month gap between operations, just in case, which is standard procedure in believe.

I also realised another thing I took for granted during this healing process, the ear is also the organ of balance. It took a couple of weeks for mine to settle down post operation, an interesting experience indeed. Once I realised what I had been missing for so long I could not wait to get my left ear operated on. I am fortunate in some respects that Otosclorosis is one of the few hearing problems that can be reversed successfully.

Through this whole experience I have very much come to understand the link between volume of sound and the way our brains perceive and interpret sound. I hope that you the readers don't have to have a similar experience to mine to believe what Alan has repeated so many times on HUG {that it is loudness which defines our hearing}, it is the truth.
 

Hipper

New member
Peak levels?

Peak levels?

Loudness trumps sound quality." Even if it's as little as 1 dB. An increase of 4, 5, or 6 dB in the whole history of analog, but over 20 years of the compact disc there was a 20 dB increase in the average level. That's amazing. It goes to show that there are a lot of industry professionals addicted to loudness.
Is this 20dB figure really true? My DAC (TEAC D/70) has a volume control with dB measurements and assuming it is reasonably accurate, based on my CDs from early to modern ones I find the range I need to adjust from various CDs is around 10dB to get what is my normal listening level, and mostly it is around 5dB.
 

Pluto

New member
Lead-up to the Loudness Wars

Lead-up to the Loudness Wars

Is this 20dB figure really true? ... based on my CDs from early to modern ones I find the range I need to adjust from various CDs is around 10dB to get what is my normal listening level, and mostly it is around 5dB.
When the CD was making its first tentative appearance, the guidelines for content creation stated that the final 10-12dB should be thought of as a safety zone only. This thinking was entirely reasonable as most of the industry's metering was designed to work well with the analogue media then prevalent – meaning that there was little point in having the meters respond to very short term overloads that a) were not audible and b) didn't trouble the equipment.

The recommended relationship between typical analogue levels and the new-fangled digital environment was that analogue line-up (conventionally 8dB below peak on analogue meters) corresponds to -18dB in the digital world, described as -18dBFS (i.e. referenced to the digital absolute maximum Full Scale). This meant that, in theory, no analogue recording would ever peak above -10dBFS (i.e. line up level plus 8dB). In practice, this wasn't entirely true because of the nature of analogue metering referred to in the previous paragraph. When examined on true digital meters, a recording appearing to stop at -10dBFS when viewed on analogue meters would sometimes peak 2 or 3dB louder, occasionally 4 or 5dB on the true digital metering: this is what the 10dB buffer zone was for*.

Those responsible for the grand design believed that the wide dynamic range offered by CD could be exploited to present the world of recorded music on a more realistic scale than had been possible on analogue media – for example, that a solo alto flute recording be presented at a realistic level compared to, say, a bagpipe band ;-) This policy could easily have led to the average levels of some CDs being over 30dB lower than others, which was seen as an advantage offered by the new medium.

The music business was (in my view, rightly) cautious about embracing such wide dynamic range and it takes a very brave record producer, in any genre, to release a product that peaks more than a few dB short of the maximum modulation of which the medium is capable. So while there are some CDs out there that genuinely follow the early guidelines which imply very low modulation for inherently quiet music, the subsequent trend has certainly been in the opposite direction, culminating in the loudness wars of recent times.

* it must also be borne in mind that most analogue metering conventions include a margin for error. Analogue recordings tend not to go devastatingly wrong if you accidentally go over by a dB or two. In fact, the effects of such overload are a major part of the ‘love’ felt for some analogue recordings. Contrariwise, digital modulation is unforgiving. At –.1dBFS it's about as near perfect as it gets. Attempt to modulate ½dB louder and you are in disaster territory.
 

Rolo46

New member
Levels and taste

Levels and taste

We found in the 90s that a Nagra played into a digital system needed 20dB of headroom relative to -8dB line up tone. That upper 12dB covered transients unknown to a BBC PPM or a Nagra Modulometer, both excellent metering devices.

Metering is now so much better, my Nagra VI shows those terrifying kicks, but they have to be accommodated in the final version somehow, otherwise average level is too low for consumers taste and kit.

Subtle adaptive compressors and limiters bring up average values and smooth troublesome transients. This must be done minimally and with taste. Otherwise we all know the end result.......
 

Pluto

New member
Fast metering and transients

Fast metering and transients

That upper 12dB covered transients unknown to a BBC PPM or a Nagra Modulometer, both excellent metering devices
It's reasonable to assume that the transient overloads not showing on the Modulometer or PPM were inaudible, hence of little consequence in an all-analogue world.

It's interesting to note that some early digital meters were, in fact, a little too sensitive which resulted, as you have noted, in under-modulation. Such meters were typically responsive to a single sample: a little later on, most digital meters were configured to respond only to four samples or more for exactly the same reasons as the most desirable attack time was defined on their analogue siblings.

Some digital metering systems are configurable in this respect – while an overload of 3 samples or less is unlikely to be audible in and of itself. Such an overload might, in some circumstances, de-stabilize the channel hence the occasional need to be aware of the issue.
 

David Schalkwyk

New member
Evidence of the limited human audio memory

Evidence of the limited human audio memory

On the issue of whether you can trust your ears, here is a link to a series of experiments by psychologists at the University of Iowa that show that our aural memory is very short indeed--it begins to decay after a matter of seconds.

Bigelow and Poremba discovered that when more than 100 UI undergraduate students were exposed to a variety of sounds, visuals, and things that could be felt, the students were least apt to remember the sounds they had heard.


In an experiment testing short-term memory, participants were asked to listen to pure tones they heard through headphones, look at various shades of red squares, and feel low-intensity vibrations by gripping an aluminum bar. Each set of tones, squares and vibrations was separated by time delays ranging from one to 32 seconds.


Although students’ memory declined across the board when time delays grew longer, the decline was much greater for sounds, and began as early as four to eight seconds after being exposed to them. While this seems like a short time span, it’s akin to forgetting a phone number that wasn’t written down, notes Poremba. “If someone gives you a number, and you dial it right away, you are usually fine. But do anything in between, and the odds are you will have forgotten it,” she says.

Overview here:

http://www.psychology.uiowa.edu/resources/features/one-ear-and-out-other

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