All this talk about binaural beats. Just exactly what are binaural beats? Let's explore this in three steps. First, we'll talk about what sound really is. Then we'll define frequency. And lastly, we'll use these two definitions to explain specifically what binaural beats are.
Back to Basics - What is Sound?
Here's my definition: Sound is the sensation our brain creates (and we "hear") when vibrations in the air cause our eardrum to move or vibrate.
We are surrounded by air - although we don't usually realize it except when the wind blows. But wind is a large and relatively slow movement - like the current in a stream. Sound is also the movement of air - but much smaller and faster movements - like the ripples on a pond.
So, what exactly is sound? When we strike a drum, for instance, the head of the drum gets pushed in. Then, because it's kind of elastic, it springs back. But it doesn't stop where it was. Because it has mass it keeps moving and pushes out (just like a swing continues to move back and forth after it's pushed). Then, the drum head elastically snaps back and continues until it pushes back in. And so on - it continues to vibrate back and forth until it runs out of energy. We see this motion as vibration because it happens hundreds of times a second.
That's how sound is created - because each time the drum head pushes out, it pushes the air in front of it. Then that air pushes the air between you and the drum until the air around your ear pushes your eardrum in. When the drum head snaps back into the drum, it sucks in the air around it. And that vacuum propagates through the air and sucks your eardrum outward. So, the drum head moving back and forth pushes the air between you and the drum back and forth very rapidly which pushes your eardrum back and forth very rapidly. When your brain senses your eardrum moving, it translates those motions into the sensation we know as sound. So it's all about air moving back and forth - and that's why there's no sound in space. No air - no sound.
What is Frequency? - The Speed of Sound
Frequency is simply how fast those sound vibrations occur. If the drum head vibrates 100 times per second it has a lower frequency than another drum head that vibrates at 150 times a second. We hear higher frequencies as higher pitch notes. So a thin string on a guitar produces a higher pitch or tone than a fat string because it weighs less so it can move back and forth faster (and therefore pushes air back and forth faster). And if we fret a string, we shorten the string and the pitch gets higher. A shorter string weighs less than a longer string (less mass) so, once again, it vibrates faster.
What are Binaural Beats? (FINALLY!)
Let's go back to our drum example - only this time, we'll be greedy and use two drums. If the drums vibrate at exactly the same frequency and if they vibrate together; the sound will be twice as loud. In other words, both drums will push out at the same time so that the air that pushes our eardrum will be twice as strong and then both drums sucking will tug at our eardrums with twice as much force.
However, if we hit one drum just a fraction of an instant after the other, one drum head will be pushing out while the other is pulling in. One drum would be pushing on the air while the other pulls on the same air - so the air won't move. In a perfectly theoretical world, the sounds would cancel. In fact that's how those new-fangled noise-cancellation earphones work. They sense the sounds around you and then pump "opposite" sounds into the earphones to cancel the noise.
Now, what if the two drums had slightly different frequencies? When one drum head pushes out, the other (because it is slower) pushes out just a little bit after it. So the sound you get is stronger than from one drum but not quite as strong as the two of them pushing air exactly together.
The next time the heads push out, the second head falls a little farther behind and the sound gets a little weaker. If the second drum falls just a little more behind each time, eventually the second drum will be pulling in as the first pushes out and the sound will be very much diminished. Then, as the second drum continues to fall behind each cycle, they will eventually sync up again and will push out together - essentially doubling the power of the sound.
You can see that as the slower drum perpetually falls behind the faster drum, the sound intensity will cycle and get weaker as the "pushes" and "pulls" line up and stronger as the "pushes" and "pushes" (or "pulls" and "pulls") add to each other.
This is what a binaural beat is. It is when two sounds differ by a small frequency, they create a pulsing known as a beat frequency. These beat frequencies or binaural beats are caused by the signals periodically adding to each other and cancelling each other.
Now, I've used drums to explain binaural beats because it's easy to imagine drum heads pushing and pulling air and interacting with our ear drums. In reality, the binaural beats that we use to alter our mental states are created electronically - and with greater precision - by computers and sophisticated audio software. And the mixing of the two signals happens inside our heads (when we listen with headphones) - not in the open air. But the principles remain the same.
What are Binaural Beats Used For?
Binaural beats can help you put your brain into a specific mind-state. Do you need to be energized? More alert? More focused? Or do you need to be more relaxed or in a meditative state of mind? Maybe you need to be in a learning frame of mind. Or do you need help falling asleep? Each of these situations requires its own specific optimal state of mind.
We already know this. If you are energized, excited or stressed; you will have difficulty relaxing or falling asleep or studying. If you are daydreaming, you are going to have trouble studying or learning something new. Every activity has an optimal mental state of mind associated with it.
The interesting thing is that our state of mind is controlled by our brainwave frequencies. When we are active and alert, our brain waves operate at higher frequencies. When we are relaxed and calm, our brains operate at lower frequencies. So, we can control our state of mind by controlling our brainwave frequency.
That's where binaural beats come in. As I explained earlier, when we present a different frequency to each ear; the part of our brain that determines which direction a sound is coming from does a kind of mental subtraction and generates the beat frequency within our brain. Then, by a process called frequency following, our brainwave frequency "locks onto" this beat frequency and is gently guided along to the desired mind state.
So, when we need to be more energized, more relaxed, less stressed, etc. - we can easily and immediately enter the appropriate mind state through the use of binaural beats.
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