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Old 24th June 2009, 07:09 PM   #11
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Hey Retroman,
Maybe this link will help

http://www.sengpielaudio.com/Acoustics226-2003.pdf
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Old 24th June 2009, 07:23 PM   #12
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some days, i can 'hear' better than others.

some caffeine seems to increase sensitivity.

most days, i been wearing ear plugs, day and night.

usually the hearos brand.

can hear much better, when the plugs are removed,

when the noise has been blocked for several days .
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Old 24th June 2009, 07:34 PM   #13
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Quote:
Originally posted by tomtt
some days, i can 'hear' better than others.

some caffeine seems to increase sensitivity.

most days, i been wearing ear plugs, day and night.

usually the hearos brand.

can hear much better, when the plugs are removed,

when the noise has been blocked for several days .
I heard that that was why pirates wore eyepatches over one eye (for night fighting). I have verified the earplug thing myself.
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Old 24th June 2009, 07:42 PM   #14
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FWIW, one of the mechanisms that we use to perceive loudness is listening for the presence of odd-ordered harmonic content. The 5th, 7th and 9th orders IOW are used as loudness cues by the human ear/brain system.

Audiophiles have terms for these vanishingly small amounts of enhancement- bright, brittle, hard, harsh, clinical, chalky... all describing odd-ordered enhancement at very small levels- usually considerably less than 1 db and often less than 1/100th% of a percent THD.

Even-orders, especially the 2nd and 4th, are not objectionable to the human ear, but we do have terms to describe them- body, warmth, lush, rich, fat, thick, muddy, depending on the level of the content, at considerably higher levels!

This is why two amps can have the same bandwidth on the bench but sound quite a bit different in practice.
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Old 25th June 2009, 01:30 AM   #15
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Quote:
Originally posted by Gabdx1
At 1khz you can roughtly discern 325 degres of intensity from 10db - 130 db, 0 db = can't hear anything.

The answer is somewhere around 1/3 db and is 'ear' dependant and frequency dependant.

The audition spectrum spread somewhere between 16-20khz.

Musicality starts around 35hz and ends at 15khz.

To be able to hear under 35 hz or over 15khz the sound pressure needs to be painful. To hear 20khz = 100db, to hear 20hz = 85db.

Ummmm... I have to disagree with the last statement.

Much depends on your physical ability to hear (how good your ears work).

When I was younger (less than 28 years old approx) I could hear into the ultrasonic range. Very easily. It was not fun. Things that most people could not hear were very bothersome.

In the LF range it is not particularly difficult to hear. High levels are not required in my experience.

So, I am unsure of what you are referring to in this case. Perhaps you are making reference to hearing something when other midband sound is present??

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Old 25th June 2009, 04:51 PM   #16
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it comes from a book 'illustrated guide of the music' my traduction. It has many references.

No human can hear ultrasonics that are over 20khz. They will vibrate your ear drum if very loud but never you will 'hear' it, the only thing you can fell is pain.

Under 16hz no human can hear, all you will 'feel is your body vibrate and ear drums vibrate , floor shake, but it is not making any sound to your brain.

just to give you an example , the highest note on a piano is around 5khz and it is very unmusical and annoying.

The hissing sound you hear of a tv, fans, motors etc are not very high, people confound it easy with ultrasound when it is really around 10khz.

Here is what I took from a website , (note : my book only says that frequency range declines GREATLY with age) :

You Need to Know
Human hearing: 20Hz - 20kHz
Healthy young children may have a full hearing frequency range up to 20,000 Hz,
by the age of 20, the upper limit may have dropped to 16,000 Hz.
From the age of 20, it continues to reduce gradually to approximately 8,000 Hz by retirement age (60 ?)

I know you can be lucky genetically and take care of your ears , i took great care of mine and at 27 I can hear up to 18khz , but at high volume level.
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Old 25th June 2009, 05:14 PM   #17
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Gabdx1, when I was in my 20s I worked at a place that had an ultrasonic alarm. It was an old school type and operated at 23.7KHz.

I could hear it well before I walked into the room it was operating in. It was only when I got into that room that I found it painful. But back in those days I could tell when my wife was watching the TV before I got into the house, because I could hear the horizontal oscillator on the front porch- through a storm door and the main front door.

The book you got your information from is accurate, in the way that generalizations always are- there are always exceptions. Some people *can* hear beyond 20KHz (or could- I don't hear nearly that high anymore but poor digital playback can still give me a headache).
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Old 25th June 2009, 06:41 PM   #18
Gabdx1 is offline Gabdx1  Canada
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Ö I can 'hear' like you say an ultrasound alarm. What I hear is not the actual high pitch sound, it is the lower harmonics, what you heard is the maybe 18khz harmonics that are painful to hear and are at high levels.

Claiming to hear above 20khz is like Jesus walking on water.

All frequency above 2khz are transmitted by the bone structure and can go through many materials, like doors, ear plugs etc.

20khz is not a generalization, it is tested as the maximum limit, all literature and all scientific tests never ever said you can hear above it.

A deaf person can feel the vibration through his body, eardrum, but he canít 'hear' the actual tone.
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Old 25th June 2009, 06:55 PM   #19
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From J. Acoust. Soc. Am. 122 3, September 2007: "Hearing thresholds for pure tones above 16 kHz" by Kaoru Ashihara

"Hearing thresholds for pure tones between 16 and 30 kHz were
measured by an adaptive method. The maximum presentation level at the entrance
of the outer ear was about 110 dB SPL. To prevent the listeners from
detecting subharmonic distortions in the lower frequencies, pink noise was
presented as a masker. Even at 28 kHz, threshold values were obtained from
3 out of 32 ears. No thresholds were obtained for 30 kHz tone. Between 20
and 28 kHz, the threshold tended to increase rather gradually, whereas it increased
abruptly between 16 and 20 kHz."

The ages ranged between 19 and 25 years.

So we can hear very high frequencies when we are a) young and b) the level is very high. In real life I don't consider anything above 10kHz as relevant.

Best, Markus
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Old 25th June 2009, 07:09 PM   #20
Gabdx1 is offline Gabdx1  Canada
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this test is false for many reasons.

1. the ear itself produce harmonics, with an impossible to hear signal the ear will produce lower harmonics within the canal, bones and receptors.

2. 110db is painfull in those frequency and is high enough to generate many sub-harmonics in the ear.

3. pink noise can't mask higher subharmonics.

4. the ear transmit the highest audible (20-20khz) signal to the brain.

5. my interpretation is that 3 of 32 participants could hear nearly up to 20khz harmonics generated inside the ear OR by the speakers.

6. sending a square wave of over 20khz result in mainly Very high level of distortion created by the amplifier and mainly created by the driver at very high volume 110 db. I would not be surprised if distortion was over 50% for the signal itself + pink noise adding to the confusion.
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