Noise induced hearing loss from frequencies > 22kHz?

[Text_Edifice]

So, help me settle a discussion.

Friend asked if hearing could be damaged by high-SPL high-freq signals outside the range of human hearing.

I reckon no as our hearing mechanism (ear drum, hair cells, cochlea, auditory nerve) can't physically respond and thus can't be damaged.

Someone else says yes....

Anyone have a definitive answer for me?

[Gian]

Rick, didn't you put one of these insect/pet repeller (50kHz) things to your ear once and got as sore ear/head for a day?

Sounds (no pun intended) like it might make a difference.

There is documentation/anecdotal evidence to say that we are aware of stuff above the 20kHz range.

[AnthonyMF]

50kHz = wavelength of 6millimeters.

So, at high SPL, I guess it could move our tympanic membrane 3 - 6 mils out of place, max, If we're imagining a small vacuum next to our ear caused by the high freq sound.

[rob]

Well here's a can of worms!
I can't answer the question definitively, but I have a thought process that goes like this:
can high SPLs at 1K damage hearing? Yep! At 10K? Sure! 18K? Why not! So what about 22K? Well your ears don't have a brick wall filter above 20K so I find it hard to envisage the mechanism by which hearing would suddenly be protected above an arbitrary frequency.

[Text_Edifice]

sure - 22kHz is arbitrary but my understanding is that for damage to be done our hearing mechanism actually has to be able to physically respond to variations in pressure at the ear drum - not just the tympanic membrane but also the hair cells whose ability / inability to vibrate in sympathy is, I recall - possibly incorrectly, is responsible for our ability to perceive high frequencies.

[wez]

well 9Hz is below the range of hearing, and at high enough SPL will rupture your aorta.

interesting discussion. 22k or higher? i vote yes... but maybe not in the way we would expect. it might not upset the drum or the hair cells, but maybe it could shatter the inner ear bones, or rupture the cochlea, or the vestibular nerve etc.

fascinating stuff. i'm sure the military is onto it.

[Kurt]

My utterly baseless guess would be yes... My hearing tops out at around 16k these days, but sounds at 20k, which I can't hear, make me feel like my head is being squashed or twisted.

[heathen]

There are some devices that keeps kids out of shopping centres at night called mosquito, these things have gone from "safe" now to "most probably unsafe" as it is believed they damage kids hearing, especially really young kids. They can cause nausea, headache and a bunch of other effects depending on SPL. Freq they emit is about 18k, some use 18k plus I think a second higher tone to cause beating and make it even more annoying (dangerous).

[Drumstruck]

....I was on a plane flight from NZ back in 1971 (yikes!) with my mum - the plane couldn't get the landing gear down and flew around for 45 mins trying to fix the problem and dumping fuel in preparation for an emergency landing.... all the while (I assume because it was flying quite low for a jet) there was a persistent squeal at about 14KHz which was quite loud. From that day on my mum couldn't hear anything over about 9-10KHz........

[AnthonyMF]

There are some devices that keeps kids out of shopping centres at night called mosquito, these things have gone from "safe" now to "most probably unsafe" as it is believed they damage kids hearing, especially really young kids. They can cause nausea, headache and a bunch of other effects depending on SPL. Freq they emit is about 18k, some use 18k plus I think a second higher tone to cause beating and make it even more annoying (dangerous).

Can we perceive the beating caused by two tones beyond our range of hearing? ie, if a device produced 20kHz and 21kHz tones simultaneously, would we hear a 1kHz tone?

[AnthonyMF]

sure - 22kHz is arbitrary but my understanding is that for damage to be done our hearing mechanism actually has to be able to physically respond to variations in pressure at the ear drum - not just the tympanic membrane but also the hair cells whose ability / inability to vibrate in sympathy is, I recall - possibly incorrectly, is responsible for our ability to perceive high frequencies.

Well, could a large enough change in pressure implode/explode the cells? If our tympanic membrane is moving, it has to be moving the fluid inside our cochlea, which must have an effect on the cells inside it, even if it doesn't cause them to move in a way that would allow them to create that electrochemical signal we love so much.

[rick]

Rick, didn't you put one of these insect/pet repeller (50kHz) things to your ear once and got as sore ear/head for a day?

Sounds (no pun intended) like it might make a difference.

There is documentation/anecdotal evidence to say that we are aware of stuff above the 20kHz range.

yes absolutely .. but it must have damaged my memory as well
how do you know this Gian ?

ultrasonic wavelengths at the right level do all kinds of things to the body that are not good (stick you head in a microwave some time )

but really most of us should be more concerned with the sounds we can hear when a band is playing
ear plugs are cool tinnitus will be a drag

[Kurt]

Tinnitus is a drag. I have a mild dose, the noise is always present but usually masked by life around me. I can't imagine what it would be like to have it severely..

but really most of us should be more concerned with the sounds we can hear when a band is playing
ear plugs are cool tinnitus will be a drag

[Gian]

Hey Rick

Either you wrote somewhere on here, or it must have been in an AT mag.

I am the same as you Kurt, playing bass and standing near the drummer.

I always use ear plugs now, people laugh at me, but I will be the one laughing in a few years time when this generation of iPod wearing youths can't hear anymore - but then they wont hear me laughing - damn it!

[rick]

ok i must have wrote it somewhere in one of my "dumb things i have done so you dont have" to moments

DO not put an ultrasonic animal scaring away device up to your ear to see if you can hear way above 20k
you can.

but do NOT do it it is VERY unpleasant

ok you have been warned !


tell me how you go

[Kurt]

Gen Y don't listen anyway

Hey Rick

Either you wrote somewhere on here, or it must have been in an AT mag.

I am the same as you Kurt, playing bass and standing near the drummer.

I always use ear plugs now, people laugh at me, but I will be the one laughing in a few years time when this generation of iPod wearing youths can't hear anymore - but then they wont hear me laughing - damn it!

[Mark Bassett]

It depends if we're talking about conductive or sensorineural hearing loss.

[Text_Edifice]

With the latter being less likely in this situation?

[The Tasmanian]

9 hz at the right volume makes all of your internal organs bleed.
Aldof Hitler used 9 hz at political rallies in small doses to make people feel ill and turn it off when he stood on stage (creating elation)
He was using speakers up to 6 foot in diameter.
Americans were using 9hz sound weapons in the first gulf war.
Tesla was the man that they got all the info from - Hitler and Westinghouse (US gov) and the Russian's were on to him 60 years ago and developed sound weapons ever since the wine glass was broken by a vocalist.
22khz - sounds like the head on a good beer to me - cant see the damage in that.

[Ben M]

Brown note anyone?....or maybe not....no not the brown note....It's not going to happen unless you really want it to happen.

I think it's safe to say that if it's loud enough it will effect us in some way...seeing our hearing/brain relates too loud things differently wether sub sonic, ultra high or anywhere in between. Our freq spectrum is one thing, but our ability as umans to be affected by the things we cannot hear (or see) is always extraordinary.

I'd presume - DAMAGING..... as long as it's loud enough. In fact I'd say the further away from our freq spectrum (20 to 20) the louder the sound would have to be to ultimately affect our hearing. But affecting us physically and manipulating peoples feelings and emotions... that's another thing.

[Alistair]

That's amazing about the 9kHz/Hitler stuff Chris, I'd never heard about that.

I'd love to know if that sorta crap still goes on today, but I suppose all the good stuff is kept secret for as long as possible.

[Kurt]

It's amazing and totally unsubstantiated..
I doubt anyone in the 1940's could actually reliably produce a 9hz signal, let alone at such volumes as to have any effect at all on a human.
Mythbusters did a pretty good test looking for the "brown note" if I remember correctly they managed to get discomfort. No way did the Germans get more impressive results 50 years earlier.

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

[DarkSky]

It's amazing and totally unsubstantiated..
I doubt anyone in the 1940's could actually reliably produce a 9hz signal, let alone at such volumes as to have any effect at all on a human.
Mythbusters did a pretty good test looking for the "brown note" if I remember correctly they managed to get discomfort. No way did the Germans get more impressive results 50 years earlier.

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

It's fair enough to be sceptical, Kurt. However the Germans did have the ability to measure frequency, and it wouldn't have been difficult at all for them to tune an oscillator to 9 Hz. Remember that their technology produced the Neumann CMV3 in 1928 and the U47 in 1947. These (and other) achievements depended on accurate measurement and test instruments.

They also quite deliberately used their advantage in audio technology (including the CMV3) to exert subtle psychological influence on the audiences of their political rallies and broadcasts. So, as far as that goes, it's a game they were well versed in.

So I'd credit that it's something that they might have done - but I'd agree that there doesn't seem to be much in the way of hard evidence that they *did*.

[The Tasmanian]

The internet is a great platform - just cause one can do a 30 sec search, does not mean that something does not exist - or work, or have any research behind it.
Mythbusters is all good cheap fun - if your into it - but I don't take much notice of them as a high end military testing organization.

There is so much more stuff out in the world on 9hz,
60-80 years of using frequency as weapons.
Films, books, scientist discussion papers, military stuff, Tesla papers.

Don't underestimate the German, Russian and US military top scientists at that time - they were desperate to find new weapons - hence the Germans and Russians desperately spying on Tesla in the US.
This was seen as the future for the world military scientists for many many decades.
Its not all about 9hz - its getting different frequencies to do different tasks.
And I would hedge a bet they are still working on it today, and they will continue for many many decades more.

Before the internet there were these great things called books - millions of them were written.

[Kurt]

Sorry! Drunk 3:30am post.. In the sober light of day I'll concede that it is possible. The Americans have a device called a sound cannon that generates a high frequency sound at over 140db. They've used it on protesters. The mythbusters thing was in conjunction with Meyer Sound, it was actually fairly well done.

[The Tasmanian]

I have a good mate in the US whose father (in the US Army on the battlefield) swears they were killing people with sound on one occasion in the First Gulf War.
It was so hush hush what they were doing not even the soldiers knew what was going on.
They would bring in a huge machines on the back of a trucks, no one would hear or see anything, then they were told to move out of the bunkers and towards the enemy bunkers where they all lay bleed to death from even through their skin. Turns their insides to soup.
They buried them on the spot by filling in the trenches to hide the evidence.

And since the invention of the audio spotlight at MIT 15 or more years ago, they have been working on localized sound weapons, like deafening a person who is standing beside another with no sound being heard by the the other person who stands in silence - using sound traveling inside a ultrasound laser beam.

Sound is the weapon that I use everyday.

[Mark Bassett]

Mythbusters did a pretty good test looking for the "brown note" if I remember correctly they managed to get discomfort.

Their 'test' was a complete sham. It proved absolutely nothing.

[Kurt]

Righto.

Mythbusters did a pretty good test looking for the "brown note" if I remember correctly they managed to get discomfort.

Their 'test' was a complete sham. It proved absolutely nothing.

[Drumstruck]

And since the invention of the audio spotlight at MIT 15 or more years ago, they have been working on localized sound weapons, like deafening a person who is standing beside another with no sound being heard by the the other person who stands in silence - using sound traveling inside a ultrasound laser beam.

wouldn't it be easier just to shoot them?

Has anyone (else) been near a big earthquake? I've never heard such a deep note as an earthquake... it didn't make me sick, but it did make me scared.

[zenelectro]

There are some devices that keeps kids out of shopping centres at night called mosquito, these things have gone from "safe" now to "most probably unsafe" as it is believed they damage kids hearing, especially really young kids. They can cause nausea, headache and a bunch of other effects depending on SPL. Freq they emit is about 18k, some use 18k plus I think a second higher tone to cause beating and make it even more annoying (dangerous).

Can we perceive the beating caused by two tones beyond our range of hearing? ie, if a device produced 20kHz and 21kHz tones simultaneously, would we hear a 1kHz tone?

If we can't hear 20kHz or 21kHz then we won't hear the 1kHz difference of those two tones. The result is 1kHz amplitude modulation due to addition (or subtraction) of the two tones, not another tone per se.

This is assuming zero distortion transmission. If those two tones were at such high level to cause distortion in the transmission through air itself then you will get side band tones produced, just
like audio intermod products through say an amplifier or whatever.

There appears to be some developement in this area with a few products already out there using ultrasonic transducers to create sound that can have extreme directivity properties.
An American inventor, Woody Norris has developed some pretty amazing stuff that is being used for military (and other) applications.

http://www.lradx.com/site/
http://www.ted.com/talks/woody_norris_i ... hings.html

cheers