Hearing frequencies

[bradenchase]

A bit of background.

I'm a beginner and was just playing around with the waveform generator in Amadeus. At around 17,700 hz (standard sine wave) I couldn't hear anymore. My wife could hear up to 21,050 which I was told isn't possible so I was proud of her for that.

Starting at about 29,000 hz, I could distinguish sound again. I kept increasing by rates of 1000 hz and reached 100,000 hz (the Amadeus maximum) and could still hear sound. I didn't test this part with my wife. I could hear an increase in pitch with every increase in frequency.

My real question is what happens at these higher frequencies. Are they overtones? Is something wrong with my speakers?:oops: (standard iMac speakers) I remember reading that iMac sound cards can't produce sound over 44.1 so not sure what's going on there. Is Amadeus not calculating something correctly?

Any insight would be much appreciated!

Thanks!
Braden

[Martin Hairer]

Hi Braden, in order to represent a signal at a given frequency (say 20'000Hz), it needs to be sampled at a frequency that is at least twice that (i.e. 40'000Hz in that case), see

http://en.wikipedia.org/wiki/Nyquist–Sh ... ng_theorem

This means that at a standard CD quality, you cannot represent anything above 22'050Hz. In any case, standard audio equipment is designed to reproduce only the audible range and not much more. (As you noticed, what really is audible varies a bit from person to person and usually deteriorates with age.)

To make a long story short, anything significantly above 20kHz requires high sampling rate and specialised equipment to be reproduced accurately. What you heard aren't undertones but rather undersampling artefacts… Regards,

Martin

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HairerSoft
http://www.hairersoft.com/



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[Lou Kash]

At around 17,700 hz (standard sine wave) I couldn't hear anymore.

If you're under 25 years old, that's still an expected value.
If you're over 30, for some it's maybe still possible, but less likely.
If you're over 40, most people don't hear anything over 15 kHz.
And from then on it goes downhill rapidly…

My wife could hear up to 21,050

Very unlikely, unless she's 18 years old… ;)

[bradenchase]

Thanks Martin and Lou!

@martin
While most of that Wikipedia article was borderline unintelligible to me, after reading through it, your explanation did make sense. Thank you for that!

@Lou
I'll be turning 28 in just over a month and my wife turns 30 a few weeks after me.

My theory is that my wife hasn't been exposed to the same noise pollution than most people in developed countries are. That's why her hearing is better.

She was born and grew up on a farm in the backwoods of Brazil. Didn't come to the city to she was 15 and even then lived on the outskirts. She never owned a car, and doesn't know what twitter is but she can hear the rain coming and can identify birds whose names I can't even pronounce just by their song. She also has significant native Brazilian genetic heritage, She told me she used to hear a lot better than she can now. I only say all of that because I'm curious to know how and when those frequency ranges were determined. Anybody know?

I, on the other hand, have been playing with leaf blowers, lawnmowers, and car engines since I was 10.

[CDJonah_alt]

I suspect the limits are somewhat artificial. My brother didn't use to
be able to stay in the same house with the TV as the IM frequency (30
khz or so) drove him crazy. I had another friend who also was bothered
by the IM frequencies but not so severely.

Chuck

On 1/4/12 9:35 AM, bradenchase wrote:

Thanks Martin and Lou!

@martin
While most of that Wikipedia article was borderline unintelligible to me, after reading through it, your explanation did make sense. Thank you for that!

@Lou
I'll be turning 28 in just over a month and my wife turns 30 a few weeks after me.

My theory is that my wife hasn't been exposed to the same noise pollution than most people in developed countries are. That's why her hearing is better.

She was born and grew up on a farm in the backwoods of Brazil. Didn't come to the city to she was 15 and even then lived on the outskirts. She never owned a car, and doesn't know what twitter is but she can hear the rain coming and can identify birds whose names I can't even pronounce just by their song. She also has significant native Brazilian genetic heritage, She told me she used to hear a lot better than she can now. I only say all of that because I'm curious to know how and when those frequency ranges were determined. Anybody know?

I, on the other hand, have been playing with leaf blowers, lawnmowers, and car engines since I was 10.




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[Lou Kash]

the IM frequency (30 khz or so)

Actually, the hearable frequency is 15625 Hz (PAL) and 15734 Hz (NTCS) respectively.
--> http://en.wikipedia.org/wiki/Cathode_ra ... ible_noise

It used to annoy me as well, but eventually it "magically" disappeared some time in my early thirties. :)
These days, with flat panels it would be a non-issue anyway.

By the way - and here comes the fun part - I'm using Amadeus primarily for its excellent sonograph feature. You wouldn't believe how many remastered (or "remastered") CDs were processed by some old farts who don't bother to double-check their studio equipment for the aforementioned 15-something kHz buzz which they likely can't hear for decades already. And apparently, their tight studio budget doesn't even allow them a copy of Amadeus for running the master audio files through its sonograph…

My theory is that my wife hasn't been exposed to the same noise pollution than most people in developed countries are. That's why her hearing is better.

Women in general apparently don't have such a high frequency hearing degradation as men.
21 kHz is still very unlikely though. In particular because you would need a high end audio system - in particular speakers - to actually reproduce this frequency cleanly.

Some more interesting links on topic:
http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml
http://www.audiocheck.net/audiotests_fr ... ckhigh.php

[rfwilmut]

The survival of your ability to hear high frequencies is a matter of luck, I'm approaching 70, and I can hear 10kHz in one ear and 11kHz in the other. This isn't at all bad, but I suppose it will get worse as time goes on.

However it's worth noting that many years ago Quad did an experiment which showed that people with no hearing above 10-12kHz could detect the effect of a 20kHz steep-cut filter being switched in - probably because of the phase shift it would produce - so continuous tones aren't the whole story.

If you are going to test your hearing, a word of warning: tweeters are not designed to take a very high level of high frequencies, which normally comprise only a small part of the overall sound power. The risk is of increasing the frequency, turning up the volume because you can't hear it, and watching a plume of smoke emerging from your tweeter.

[bradenchase]

Great comments everyone! I learned a ton!