Cochlear nonlinearities

[JanRSmit]

3 hours ago, Fokus said:

 

Example: it you press an ultrasonic exciter to your skull (have fun), your will hear something. Does this demonstrate ultrasonic audibility (or rather detectability)? Yes, in a way. Does this rely on intermodulation? Yes, most likely. Is this relevant for audio reproduction in the context we are interested in? No, probably not remotely.

 

 

Is this proven, or your assumption.?

Many years ago, audax had a tweeter going to over 40khz. We did a test plating the tweeter out of sight in a room and played a 30khz tone. When people came in the room for meetings, after a short while they became restless, sort of disturbed, but no clue as what caused it. Then after stopping playing, the restless behaviour dissapeared. I also remember Goldmund , just started then, referred to research by military dealing with human audibility of impulses, concluding that the audibility threshold is well above 20khz. 

[JanRSmit]

On 7/6/2019 at 3:16 PM, John Dyson said:

Are you claiming that all senses of vibration are encompassed in what is heard?  That kind of 40kHz audibllity might not be through hearing, but another sense of vibration.   I can detect some kinds of vibration from senses other than hearing.

 

Even if the 'ears' detect that vibration, people weren't saying that they 'heard' the vibration, but rather they became 'restless'.  Okay, some kinds of so-called music makes me restless, but obviously not the same mechanism as the 40kHz vibration does.

 

John

How we as human beings sense vibrations is definitely not limited to our hearing system. And how we interpret the vibrations we sense is not only music of noise. It also triggers emotions and body movements like tapping with your feet, etc. 

 

 

 

[JanRSmit]

On 7/5/2019 at 2:37 AM, jabbr said:

With respect to the question of whether audio frequencies >20 kHz might have an effect on audio perception, it has been often assumed that:

 

1) assume cochlea acts linearly

2) assume basilar membrane does not vibrate >20 kHz due to the anatomy of the cochlea

 

The question really comes down to whether the cochlea acts linearly because if not, then just as high frequency electrical components can cause intermodulation distortion (IMD) so might ultrasonic frequencies affect audio perception.

 

[1] This paper discusses: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6366996/#R30 -- in  particular look at figure 6 -- the thick black line shows response at 22 kHz and presumably greater frequencies!

 

[2] This paper discusses the mechanics of basilar membrane vibration in detail: https://pdfs.semanticscholar.org/6f0a/46befffa8710ebb606ed3dec06d7be317be1.pdf?_ga=2.6977266.115791992.1562285968-561089348.1562285968

 

There are, of course many other scientific papers which bring the notion of cochlear nonlinearities into discussion, and provide mechanisms for ultrasonic effects but these two might give folks a start.

 

The folks who assume there is some absolute law of biophysics that allows the cochlea to be modelled linearly might want to read and understand these in detail --- the situation to me is not so perfectly clear.

 

Feel free to post other scientific studies which either support or refute these ideas (there are many many)

 

As dat is i onderstand this stuff, it for one confirms that for audible sound levels up to about 50 decibels our hearing system is quite linear. Above that level of becomes increasingly non linear. In the late 70'ties this was already explained to me by medical hearing specialists.

 

Makes you wonder if this is taken into account with listening tests .

[JanRSmit]

Ginny that recordings side is considered more pure. I visites a mixing and mastering specialist and whilst very impressive, i also leaned that what we get as music has no pureness whatsoever, bar an isolated case. At least in the pop music space.