Distortion of human hearing

[PMA]

In the Pass Labs section there is a thread about human hearing. John Curl was describing his experiment with changing the slope of square-wave 5kHz signal from some 1us to some 5us and the audible effect of it.

I was told about experiments with addition of ultrasound signal, emitted by high-frequency el/ac. converter, to the audio band signal and audibility of this.

I would like to ask following question: what do you think about intermodulations inside human ear?

[tschrama]

Hi,

question: what do you think about intermodulations inside human ear?

It's there ... and used everyday in hospitals and audiology centres as a standard test. It's realetively easy to measure. You cab go to your docter and say ' I want my intermodulation distortion of my ears measured', he will probably go ... but if you tell him you got bad hearing and want a full check-up, you'll probably get your ntermodulation measured too ..

In the Netherlands many (all?) childeren get such a test, even before they can talk because it tells someting about the functioning of the inner ear without using a subjective patients feedback.

Regards,
Thijs

[poulkirk]

There is no doubt that Human Hearing suffer from Loudness Related Distortion Effects

There are well documented Loudness versus frequency curves available showing these effects being a form of Hearing Distortion in itself

At Very High Sound Levels, sensitivity to subtleties of musical sounds appear to become lost or masked

Examples are "Disco Night Clubs" or overly loud PA Systems at concerts

I feel certain that the Ear can overload, and in the process produce both Harmonic and Intermodulation Distortion, and maybe even Clipping at excessive Sound Levels

Many recent Pop Recordings are devoid of the subtleties that makes listening to recorded music pleasurable

This is likely caused by monitoring at excessive Sound Levels during the recording or mastering processes

In other words, the ears of the Recording Engineer, or Mastering Engineer, or both distorts making the final CD sound like "Crap"

[PMA]

Yes - I am thinking preferably about non-linear distortions, equal loudness contours are well known.

[vic2]

The sensitivity of the ear is controlled by a couple of muscles: tensor tympani and stapedius.

[PMA]

Well - I shoul say why I was starting this thread. The reason is as follows: experiments show that extending the high frequency limit of the audio chain does not necessarily results in better subjective appreciation of such changes.

[mikek]

Do ears have a flat frequency response through the audio band?

[Steve Eddy]

Originally posted by mikek
Do ears have a flat frequency response through the audio band?

Nope. Here are the ubiquitous Fletcher/Munsen, Robson/Dadson equal loudness curves.



se

[poulkirk]

It is doubtfull that the Human Ear has a Flat Frequency Response, but how do you measure it

The Fletcher-Munson Equal Loudness Contour curves suggest that the response is not flat, and the ear has the grearest sensitivity for frequencies between 3 and 4 KHz

Moreover, the sensitivity to frequencies vary with Loudness

Hearing Loss usually manifests itself at the upper frequencies first, usually due to ageing

Sometimes due to Ilness of various types

Don't know too much about this particular subject

Hearing can also be damaged by very loud Industrial Noise Levels, or instantly if you stand too close to something exploding

[Nelson Pass]

The ear has lots of mechanical faults, but don't underestimate
the neural power of the brain to interpret sound and music.
I think it's a lot more powerful than is generally given credit for.