new and confused

[zaf88]

im wondering something here and im sure its been answered here a million times but i cant seem to find the answer:

the sony headphones recommended only go to 10hz...but i thought you had to go lower than that for different brainwave patterns. what gives>?

[pollyanna]

Hi zaf and welcome to the community

Here's your answer which I have copied from the link below:-
"Twenty Hz is the limit at which the human ear can resolve a "pitch" from a sound. It is not the limit at which the vibrations from sound can be perceived. Below 20Hz they are simply perceived as beats, not as a musical pitch. But you do hear them, and your brain does entrain to them."

Info on Midnight Express?

Hope this helps and I wish you much peace and joy

[zaf88]

thank you that answers part of the question. But when most headphones dont go below 20hz and almost none below 10hz, how does the sound below 10hz get to your ears if the headphones cant reproduce sound that low?

[GilesC]

Hi Zaf,

to add to Polly's reply, if you take two frequencies of audible frequency (one for the left ear and one for the right), but one frequency is slightly different to the other, this creates a lower frequency 'beat' where the peaks and troughs of the frequencies match or cancel each other out. It's the combination of the higher frequencies that are combined in the brain that creates the lower frequency of beat, due to them not being identical frequencies. By combining different frequencies on the left and right, different lower beat frequencies can be generated within the brain.

Hope that makes sense.

Hugs

Giles

[zaf88]

i see so if u have a 40 in on ear and a 35 in the other u get 5hz? is this scientifically proven in real life or is it more of an unproven theory

[GilesC]

Not quite like that, but yes I am talking scientifically.

Sound is made of waves (sound waves hehe!) and those waves have peaks and troughs (the top and bottom of the waves). The frequency is how quickly the waves go from a peak to a trough, so the higher the frequency the more waves per second.
Now, if you have two waves of different frequencies, the peaks and troughs will occur at different times. At some point, let's call that the start, the first wave of each frequency starts at the same point so the waves start of synchronised, but because one wave is going up and down more quickly than the other, the peaks and troughs go gradually out of sync and then gradually come back to a point where they are in sync again. Where the two waves are in sync, the peaks of both waves are at the same point, and the sound adds together to give a large peak, and when the peak of one wave is at such a point that the other wave is at a trough, the sounds work against each other and have a cancelling out effect. The same when two troughs are in line etc. It is the frequency at which the two waves come into sync and go completely out of sync that creates the 'beat' sound... a third frequency made from the combination of the two frequencies... where it's peaks are where the two peaks combine, and it's troughs are where the two troughs combine, and the bit in the middle where the peak of one is cancelled out by the trough of the other. The frequency of this 'created' third wave will be less than the frequency of the waves creating it (unless the two waves are the same frequency, in which case it will be the same), as it's how quickly the waves come into and go out of sync.

This is similar to other waves, such as the waves created by two stones thrown in a pond, where the ripples of the waves overlap and create an interference pattern... the peaks of those waves adding together or the peak and troughs cancelling each other out. This is standard science relating to waves, and is even seen in quantum physics when they talk about the interference pattern caused by a quantum particle in the double-slit experiment (where they are investigating the fact that quantum particles act like waves or as particles, depending on whether they are being observed or not)

So, it's not quite as simple as taking one frequency away from another and saying 40 and 35 will give a 5hz frequency beat... but yes it is a scientific principle and yes the frequency of the result will be less than the two that create it.

Hugs

Giles