The human ear and examples of natural heterodynes

: >Let's see what wackypedia says about it. : >

: >"This article or section contains too much jargon and may need : >simplification or further explanation." : >

: >"heterodyning is the generation of new frequencies by mixing two or more : >signals " : >

: >

: >

: >: The amplitude modulates with an : >: apparent cusp (not sine wave) envelope. I would suppose : >

: >We'll ignore suppositions and "not sine waves" : >and go directly to simple sine wave addition. : >

: >Looks to me as if Greysky (whom you rudely snipped even it is his : >post I was answering) experienced heterodyning as he claimed. : >Yes a difference, and a heterodyne, easily. : : Sorry, simply summing two signals to obtain an amplitude beat : frequency is not hetrodyne. : : ------------ :

Oh, a linear op-amp won't add two signals?

: In order to get sum and difference sine waves via the hetrodyne : effect, nonlinear mixing is required. : This is explained in pretty : much any primer on the subject, and has been hashed to death here on : SED in the past few years. With sound levels and frequencies within : the range of human hearing the propogation of sound in air is linear, : and therefore hetrodyning cannot occur. Greysky's physics professor : was right. :

Oh really? I'll throw away all I ever learned about analogue computing, then. It won't matter, Concorde has been scrapped now anyway after 30 years of success. If I'd know it wouldn't work because SED said so I'd have never got involved. Pity it did or I could have saved myself the trouble.

You chose to mention it. Most people gloss over obvious typing errors, when the meaning is obvious in context.

John

: >>

: >>Let's see what wackypedia says about it. : >>

: >>"This article or section contains too much jargon and may need : >>simplification or further explanation." : >>

: >>"heterodyning is the generation of new frequencies by mixing two or more : >>signals " : >>

: >>

: >>

: >>: The amplitude modulates with an : >>: apparent cusp (not sine wave) envelope. I would suppose : >>

: >>We'll ignore suppositions and "not sine waves" : >>and go directly to simple sine wave addition. : >>

: >>Looks to me as if Greysky (whom you rudely snipped even it is his : >>post I was answering) experienced heterodyning as he claimed. : >>Yes a difference, and a heterodyne, easily. : >

: >Sorry, simply summing two signals to obtain an amplitude beat : >frequency is not hetrodyne. : >

: >------------ : >

: >heterodyne: 1. To generate new frequencies by mixing two or more : >signals in a nonlinear device such as a vacuum tube, transistor, or : >diode mixer. (188) Note: A superheterodyne receiver converts any : >selected incoming frequency by heterodyne action to a common : >intermediate frequency where amplification and selectivity (filtering) : >are provided. 2. A frequency produced by mixing two or more signals in : >a nonlinear device. (188) : >--------------- : >

: >In order to get sum and difference sine waves via the hetrodyne : >effect, nonlinear mixing is required. This is explained in pretty : >much any primer on the subject, and has been hashed to death here on : >SED in the past few years. With sound levels and frequencies within : >the range of human hearing the propogation of sound in air is linear, : >and therefore hetrodyning cannot occur. Greysky's physics professor : >was right. : >

: >

: : Get two sinewave generators and two loudspeakers and try it. You : certainly *will* hear the near-zero-beat difference frequency. The ear : is acting as an envelope detector. : : Try it. : : John

Nah, it has been hashed to death on SED in the past few years, it can't possibly do that if SED says so. Beats me how piano tuners did their job when they can't hear a beat because SED hashed it to death.

Even if it's perfectly linear, at low difference frequencies it (and the brain connected to it) act as an envelope detector. If you like, you can consider differentiating between "sound" and "no sound" to be a nonlinear process.

John

On Wed, 02 Jan 2008 22:36:29 -0800, greysky wrote: ...

Your professor is obviously an idiot.

"How could it be 'impossible'???? I've just _EXPERIENCED_ it!"

The secret is nonlinearity, likr the ear's logarithmic response.

But usually academia has severed its connection to reality.

Good Luck! Rich

No, the effect is not Doppler at this small scale. The 'tremolo' is just amplitude shift caused by varying distance. The frequecy shift of the Walkman's LO is due to minute component movements caused by squeezing/'massaging' the Walkman.

Ok, I've never played witn one.

: >"John Larkin" wrote in message : >news: snipped-for-privacy@4ax.com... : >: On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles" : >: wrote: : >: : >: >

: >: >"John Larkin" wrote in : >message : >: >news: snipped-for-privacy@4ax.com... : >: >: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles" : >: >: wrote: : >: >: : >: >: >

: >: >: >The tinnitus is a defect in the nervous system, the nerve ending is : >: >sending : >: >: >a false signal to the brain. Frequency selective deafness is a result : >of : >: >: >fine hairs in the cochlea breaking off. It is these hairs that vibrate : >in : >: >: >sympathy (resonate) with the sound and stimulate the nerve endings. : >: >: >They fracture with age and with use. : >: >: >Your physics teacher was right, ears do not whistle. Perhaps : >: >: >he misunderstood your question as I first did, I had it to read : >: >: >it through twice because you seem to imply that the ear causes : >: >: >sound to be emitted. : >: >: : >: >: google "SOAE" and you'll fine stuff like... : >: >: : >: >:

: >: >

: >: : >: Nobody will ever convince you of the existance of things that you are : >: determined to not believe. : >

: >This is true, but not relevant. I made no statement of disbelief. : >

: >

: >: And nothing will likely ever improve my : >: typing. As disabilities go, I prefer mine. : >

: >I'm sorry to hear you are disabled but that too is irrelevant regarding : >"The human ear and examples of natural heterodynes" : >

: >

: >

: : You chose to mention it. Most people gloss over obvious typing errors, : when the meaning is obvious in context. : : John

This is getting dreary. Over and out.

OK, but google the SOAE stuff. Ears can produce sounds.

John

Non-linearity is not necessary. When two tones are added linearly you effectively obtain a modulation of a sinusoid having their average frequency by a sinusoidal envelope having a frequency equal to the difference in the frequency of the tones.

It is rather difficult to understand how aging or tinitus could disable the ear from hearing that modulation when the frequencies are close so that the modulation frequency is low.

Bob

Of course you will hear the beat frequency, but that does not make it the result of hetrodyning.

: >"John Larkin" wrote in message : >news: snipped-for-privacy@4ax.com... : >: On Thu, 03 Jan 2008 17:47:16 GMT, "Androcles" : >: wrote: : >: : >: >

: >: >"John Larkin" wrote in : >message : >: >news: snipped-for-privacy@4ax.com... : >: >: On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles" : >: >: wrote: : >: >: : >: >: >

: >: >: >"John Larkin" wrote in : >: >message : >: >: >news: snipped-for-privacy@4ax.com... : >: >: >: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles" : >: >: >: wrote: : >: >: >: : >: >: >: >

: >: >: >: >The tinnitus is a defect in the nervous system, the nerve ending is : >: >: >sending : >: >: >: >a false signal to the brain. Frequency selective deafness is a : >result : >: >of : >: >: >: >fine hairs in the cochlea breaking off. It is these hairs that : >vibrate : >: >in : >: >: >: >sympathy (resonate) with the sound and stimulate the nerve endings. : >: >: >: >They fracture with age and with use. : >: >: >: >Your physics teacher was right, ears do not whistle. Perhaps : >: >: >: >he misunderstood your question as I first did, I had it to read : >: >: >: >it through twice because you seem to imply that the ear causes : >: >: >: >sound to be emitted. : >: >: >: : >: >: >: google "SOAE" and you'll fine stuff like... : >: >: >: : >: >: >:

: >: >: >

: >: >: : >: >: Nobody will ever convince you of the existance of things that you are : >: >: determined to not believe. : >: >

: >: >This is true, but not relevant. I made no statement of disbelief. : >: >

: >: >

: >: >: And nothing will likely ever improve my : >: >: typing. As disabilities go, I prefer mine. : >: >

: >: >I'm sorry to hear you are disabled but that too is irrelevant regarding : >: >"The human ear and examples of natural heterodynes" : >: >

: >: >

: >: >

: >: : >: You chose to mention it. Most people gloss over obvious typing errors, : >: when the meaning is obvious in context. : >: : >: John : >

: >This is getting dreary. Over and out. : >

: >

: : OK, but google the SOAE stuff. Ears can produce sounds. : : John

Very insistent that I listen to your interests, aren't you? Here is my reply again, a little more emphatically: NO!

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IAM SOOSORY TO YOU OK THANK YOU

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And don't forget the phenomenon of *binaural beats* (or heterodynes) which *are* produced entirely within the brain and by the brain. This occurs when stereo headphones are used to put tones of slightly different frequency into each ear, e.g., say a tone of 300 hz into one ear and 310 hz into the other. The brain itself decodes the difference, and 'hears' the 10 hz beat note. The effect is producible only in the sub-audible range below 30 hz or so, and overlaps the natural brainwave states. This makes it useful in brain function research and for purportedly "inducing" desired brainwave states such occur in dreaming, relaxation etc. Try a Google under 'Binaural Beats'. oc

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Strange; i had thought that it was fairly known that hetrodyning was easy to do and common. And i think that it is well known that the ear is nonlinear like the eye.

AFAIK this is true.

"Beat", "vibrato", call it whatever. The point is, the 10 hz difference note is generated entirely within the brain, which makes it of interest in a context related to the OP's original subject.

Why is it that the "pictures" show as empty boxes, but when i right-click to view image, *see* it and go back, the box is still empty?