Sound Created by the Brain?

I don't doubt that each ear, and your brain, can hear two different frequencies.

I doubt the other. What do you consider the, "frequencies below the normal hearing range" to be?

This sounds like the phenomenon of "beats," in which two sound waves of nearby frequencies add up to a low-frequency sound. This is useful in tuning pianos and other instruments.

I'm not familiar with that, but I saw a show on.....I think Animal Planet the other night about forest elephants. They made a recording during the night in a clearing where the elephants hung out. When replayed at normal speed, it was nearly silent.......when played back 3x faster, communication between the elephants was clearly audible. They were communicating at frequencies below our range, speeding up the recording made it audible.

I heard a report once on scientists trying to find out why some voices carry while similar voices didn't. Examples were the opera singers who don't use amplification, and drill sergeants. When controlled for volume and for pitch, some carries and some didn't.

They found that the voices that carried, had additional tones above the frequencies humans can hear.

There is an explanation of Tornado's point at this link, which I use to tune the guitar that I hope to learn to play.

Go to "Just getting started", here.

This research is a bit "sixties" and I'm not sure what, if any, scientific documentation of the effect is available - the binaural beat is what it's called. The sound and light entrainment theories/devices are (to the best of my knowledge) based on research results which are fairly equivocal. Afaict, there's not a strong statistical predictive value for effects of these techniques on individuals (as with hypnosis, susceptibility is variable).

Normal range of human hearing is above 20 hz, the infrasound frequencies below that can be felt but not 'heard' per se - by a human.

Great idea, Kramarat, if we speed everything up X3 we should be able to hear the elephant in the room!

He said 3 x faster not 3 x as fast.

What you actually hear is harmonics, and they are not below human hearing range, but their modulation is ringing at very low rates, even below 1 Hz.

If you had only one functional ear, you should still be able to hear the effect.

Yahlasit

If I turned the volume way up, I thought I could hear such a sound whenever the OP responded to a question in this thread: Liquid Piston Turbine Engine.

In fact it is pretty simple; see, the brain is not a sound mixer, both sound frequencies create a patern where they interfere with one another OUTSIDE of your brain, then you perceive a slow drifting siren-like sound, the closer both waves are, the higher the resulting sound, until they coincide for just a moment, then start drifting away from each other, giving you a low pitch sound, the cycle repeats.

Try overlapping two frequencies on a scope display and you'll understand it in an instant.

Do you remember the story of a little black kid, son of white mother and black father? every time he saw his father, got scared and ran to mom screaming: boogeyman ! boogeyman!!. There were no mirrors in the house.

Have a good one, and happy new year !!

Yahlasit

Hello Yahlasit,

Actually, the brain is a sound-mixer, of sorts. There is a field of study called psychoacoustics (psycho as in psychology, not as in psychopath ) studying the perception of what we hear, compared to the scientific measurement of what is heard. One simple case in point is that a change in SPL of 3dB is a factor of 2 (twice or half, depending on the direction of the change), however 10dB is perceived as twice or half as loud. Most often, these studies lend themselves to issues of intelligibility, but there are many other psychological factors as well.

I am familiar with the harmonic differences between different signals, and this is used currently to create audible sound from inaudible high frequencies. Ultrasonic transducers can be caused to create a beat frequency that is not only audible, but can be steered and directed ... a pretty neat 'trick' in acoustics. It has been done some in very esoteric home audio systems, and also for military applications (annoying noises toward the 'bad guys' but not toward the 'good guys').

Acoustics can be tricky, but it's nothing compared to the brain. Just as there are optical illusions, there are also acoustic illusions. Although I am not familiar with the OP's idea, I would not be surprised to find at least a seed of truth to the story ... the only thing that baffles me is, exactly what does a sound below my range of hearing sound like? I have felt VLF audio signals before, down to about 10Hz, and that was not exactly comfortable.

Kind regards ...

Hi DCaD:

Went out for the new year's eve. I absolutely agree with you, what I want to state is that the brain is not capable of processing acoustic waves, but electrical signals.

Regards

P.S. The bad guys, being bad as they are, might find the annoying noises actually pleasant.

Yahlasit

both sound frequencies create a patern where they interfere with one another OUTSIDE of your brain,

See my post #32. It seems that a beat frequency can be created INSIDE the brain, either electrically, or (this seems very unlikely) by mechanical sound conduction from one ear, through the brain, to the other ear.

I think you're only classed profoundly deaf when you can't hear via your skull/skeleton, so transmission is there, but still sensing is via the ear/vestibulocochlear nerve

Speakers would have higher efficiency than head phones in the 100 Hz frequency range.

2¢

Here is an article that might apply: http://gnaural.sourceforge.net/

Hello SAK ...

Good Answer ... and welcome to CR4 .

Kind regards ...

Thank You

Try reading that again leaving out the word "binaural". Yes, it is true that "a signal of 100 Hz delivered to the left ear and a signal of 107 Hz delivered to the right creates a beat of 7 Hz" (which is inaudible, i.e. it is not processed by the ears). It is also true that a frequency of 7 Hz is within the alpha range on the EEG. What is not true is that this inaudible 7 Hz frequency difference stimulates the production of 7 Hz electrical brain waves. This is where binaural pseudoscience parts company with reality.

100 Hz delivered to the left ear and a signal of 107 Hz delivered to the right creates a beat of 7 Hz" (which is inaudible, i.e. it is not processed by the ears).

I think that is not quite right -- or maybe I am misinterpreting what you wrote. The beat frequency is perceived as a volume fluctuation and that fluctuation is clearly heard when (for example) tuning a guitar or piano (and other instruments). As you approach being "in tune" the beat frequency slows down, and when it becomes so slow that you can hardly perceive it, the two strings are considered "in tune". A beat from less than one Hz to 10 Hz or so is easily perceptible. As the beat frequency gets closer to 20 Hz it begins to sound more like a growl superimposed on the string frequencies.

I think that phph is right. The brain perceives an 107 Hz sound with one ear, 100 Hz with the other. The processing is done in the brain, there is no perceivable difference/sum of the two waves. You see a blue light, separately you see a yellow light but your brain perceives as shadows of green according to the intensity of each, if you watch them both.

I wonder if the experiment has been done with 250 Hz and 150 Hz. Did the subject hear 100 Hz or 400 Hz?

As for frequencies below 10 Hz, my impression is that you perceive them in your gut (literally). But I haven't studied any of these, in extenso, so I might be....almost right!

I wonder if the experiment has been done with 250 Hz and 150 Hz. Did the subject hear 100 Hz or 400 Hz?

Check out my post #32. 250 Hz and 150 Hz together sound exactly the same through earphones or speakers: harmony. The fundamentals seem audible, the beat (100) seems inaudible and the sum is absent.

In his EEG research, Oster discovered that when different vibrations, or sound frequencies, are delivered to the brain separately through each ear (as with stereo headphones), the two hemispheres of the brain function together to "hear" not the external sound signals, but a third phantom signal.

This is not true, as far as I can tell. You can try this yourself, if you have good earphones that enclose the ears. When you put 100 Hz into one ear and 107 into the other, you do hear "the external sound signals" in essentially the same way that you hear them through speakers (with the sounds mixed in the air). You also hear the variation in amplitude we call a beat.

He seems to be suggesting that the beat is in the alpha range and not audible. What is heard either through the air (mixed) or through headphones is a frequency between the two, varying in loudness at a rate equal to the difference in frequency.

"Hearing" beat frequencies of about 1 to 10 Hz is very common in tuning guitars. Of course, the frequency that the ear responds to is in the audible range -- only the amplitude variation is at a lower frequency that has nothing to do with the ear's ability to respond.

In any case, the sound from speakers and earphones is very similar. I experimented with placing one headphone against my temple, mouth, etc to see if there could be sound conduction from right ear to left ear, but was unable to recreate the beat (or perceive the combined left/right volume) at high or low volume, unless both earphones were on my ears. At a volume at which the tones become inaudible with the headphone lifted about 2" from the ear (which produces a moderately loud sound with both earphones on) I cannot imagine that any meaningful amount of sound is conducted through the brain via mechanical vibrations.

It seems that the brain can perceive the beat frequency via headphones even when there is

• no audible cross talk at all between channels
• when there is no apparent means for physical conduction of sound from ear to ear

In short, I think Oster is wrong, at least in the way this quote is worded. There is no "third phantom signal." There is only the normal beating that any guitarist can describe. His "not the external sound signals" appears completely wrong. One hears sounds indistinguishable from the external sound signals.

The only way in which the experience is different between speakers and headphones is the apparent envelope of the beat. The beat, heard through speakers seems more dramatic.

Interestingly though, when the beat is 1Hz (frequencies 150 and 151) it is barely audible through earphones but very distinct through speakers. Also, when the beat frequency is about 20 Hz, (150 and 175)through earphones one hears the fundamentals, with a slight superimposed growl. Through speakers, the fundamentals become almost inaudible (halfway between the speakers) and the growl is pronounced, sounding a little like an idling lawnmower. So maybe there is something to Oster's observations: It seems that the beat frequency is perceived differently, speakers vs earphones, if the beat frequency is low (1Hz) or high (20 Hz) but perceived similarly when it is around 4 - 10Hz.

You can download a free tone generator. There are many, but the one on this machine is NCH.

Not to disagree in any way, the beat that we hear is the variation in loudness of an underlying frequency (itself being the average of the two input frequencies) that is within in our range. If the frequency of the sound itself was the beat frequency, we would not hear it, we might feel it though.

There may not be as many acoustic illusions as optical illusions, but an "endlessly rising tone" can be made by starting a tone at low frequency and amplitude. For a time, increase both. Then continue to increaase the frequency while decreasing the volume--but at the same time start the process over. The overlapping effect is undeniable--and rather spooky.

I recently got an earbud radio. With regular speakers, the sound seems to emanate from them or points between; with earbuds or headphones, the sound seems to emanate from within one's own head.

The most of radios and every tv's are based in this principle.Every phisics book that tries acoustic try this of mix or heterodin the frequencys.Same with technical books of electronics applied to radio: Always you mix two differents frequencies but close,after pass thru a no linear amplifier you get some new frequencies :f1-f2,f1,f2,and f1+f2.This is not subjetive.If this happens applying two close frequencies to diferents ears is a new thing for me.If we could hear the sum or difference of frequenies which are into the audible range not being each one is an excelent question : please tell us the anwer when you get.-

another person spoke of "brainsync" he was a monk for years and meditated on sounds. theoretically the brain produces a "third" beat. its not really science yet, but probably true. his cd's are relaxing but you can download reiki music for free and it help relax, if that is what you are after. i studied at Harvard, where Herbert Benson,md studied the monks for a few years and now it is science **** http://harvardscience.harvard.edu/directory/programs/mindbody-medical-institute http://hms.harvard.edu/public/news/2010/041410_corey/ Harvard Medical School CME - Clinical Training in Mind/Body Medicine Herbert Benson, MD Harvard Medical School- CME 641 Huntington Ave Boston, MA 02215 617 432 1525 its a CME course you can take. it helped me relax a lot and now i am trying to teach it. it was meant to help physicians relax

I think if you check "Kelly Howell" was no monk, but collaborated with neuroscientists and biofeedback therapists, to help creat the BrainSysn Program and company.

And the last time I check monks do not own company's or write books.

And the last time I check monks do not own company's or write books.

The Dalai Lama calls himself a simple monk, but he has written many books.

"Kelly Howell" was no monk, and second of all this is a female not male or he

I'm sorry to repeat myself, but there is science and there is pseudoscience. There are people out there who make a good living from peddling pseudoscience to the credulous, whether it be selling them unnecessary vitamin pills or ineffective lifestyle gadgets or magnetic water purifiers.

This concept of "binaural beats" affecting the brainwaves is pseudoscience. A less polite name for it is tishbull.

There was an interesting and lively discussion on this sort of thing in this CR4 thread.

Microwave hearing - They can modulate it in, or any other brainwave pattern.

This doesn't prove anything, but I was looking to see if I could find a quantitative value for the perceived difference in two frequencies, as in tuning a guitar.

Actually , your reference says that the beat frequency is f1-f2.

The Wikipedia article explanation agrees, and may be slightly clearer:

• If the two starting frequencies are quite close (usually differences of the order of few hertz), the frequency of the cosine of the right side of the expression above, that is (f₁−f₂)/2, is often too slow to be perceived as a pitch. Instead, it is perceived as a periodic variation of the sine in the expression above (it can be said, the cosine factor is an envelope for the sine wave), whose frequency is (f₁ + f₂)/2, that is, the average of the two frequencies. However, because the sine part of the right side function alternates between negative and positive values many times during one period of the cosine part, only the absolute value of the envelope is relevant. Therefore the frequency of the envelope is twice the frequency of the cosine, which means the beat frequency is: f_beat = f₁ − f₂

A (somewhat unrelated) comment on the above "is often too slow to be perceived as a pitch.":

This suggests (as a corollary) that if the beat frequency were high enough to be audible as a "pitch", that you would hear a third pitch equal to the difference. In practice this is not the case, it seems to me. For example, if you play on a piano, A2 (110Hz) and C3 (130.8 Hz) you have the first two notes of an A minor chord. You perceive the two notes in harmony, but do not perceive a 31 Hz tone. (At least I don't -- but maybe the subconscious perception of that 31 Hz tone is part of what I think of as harmony?)

Oops. I read it through, and had it at the difference, but picked up the wrong part to post when I went back to check. (It was one eye that was doddery, and getting in the way).