Psycho Acoustics (how the brain reacts to sound)

Why is it that sometimes a certain tune catches our ear? We know everything there is to know about how the ear works mechanically, but what happens between the ear drum and the brain? Psycho-acoustics is what this phenomenon is called. If you don’t think it is a phenomenon, answer for me the question I ask everyone about their taste in music: why do you like it? Everyone has an answer, it’s the beat, it’s the lyrics, the melody, and the instrumentation, whatever. All of these things aren’t really why you like music though. These are simply mechanical properties of sound waves that our ears send to the brain which then decides what you think of the sound you just heard. There are people who enjoy listening to classical music while others find it boring, both here the same sound with the same acoustics properties, so why does one person like it and the other doesn’t?

This isn’t about the ear. This is about the brain. Once the sound leaves the auditory nerve and enters the cerebral cortex something happens, and it happens differently for every person. This post is going to try and figure out why.

First let’s start back at the beginning, the ear. Like I said, every sound has set mechanical properties as the wave propagates through air. The ear has a series of tools to figure out what these are, the ear drum determines the frequency response of the sound, the middle ear then decides how loud the sound is, and the inner ear has cilia to send this mechanical vibration into a electric signal to send to the brain. I believe that this mechanical process of the ear does have an effect on our music tastes. It’s easy to make a broad statement and say everyone is born different so of course the exact shape of all those ear parts is going to be different, but what does it mean?

The ear drum being shaped differently, even in a matter of micrometers, can affect the way it initially responds. Every sound, aside from flat frequency sine waves used for testing, is made up of hundreds of poly-harmonic frequencies. This is why a trumbet sounds different than a guitar even when they play the same note. Our brain doesn’t overload with information on each frequency, instead finding the “brain averaged” response of all these poly-harmonics. The ear drum will always vibrate at the same frequencies of the sounds going into it, but the amplitude of each frequency is what varies by size of the ear drum. A smaller ear drum will have a different set of resonances (the “sweet spot” of any vibration) than a large one, therefore affecting your individual perception of the sound. For example, let’s say your ear has a resonance at 200Hz frequency. When you hear sound, and that frequency is within the harmonic makeup of the sound, your ear will vibrate at maximum amplitude at that frequency causing it to change the “brain averaged” response that you hear compared to someone who does not have a resonance at 200Hz. I feel that this is getting overwhelming very fast but bear with me.

The next part of the ear are the oscicles, the 3 tiny bones in your middle ear that transfer the mechanical vibration of the ear drum to the inner ear, which is filled with fluid. For you scientists and engineers out there, this basically changes the units of the sound so that the brain can understand it. The brain doesn’t speak mechanical vibration, it speaks electric impulse. Since these bones are directly attached to the ear drum, they also each have their own resonances. This creates even more poly-harmonic diversity from one person to the next.

Now I will bring you out of nerdy acoustician mode and into music theory mode. I hear the song “baby” by justin beiber, my brain lashes out in disgust and commands me to make it stop. A 12 year old girl hears this same exact song, and can’t get enough of it. It isn’t just because she doesn’t know any better (hopefully she doesn’t), her ear drum is differently shaped than mine, and fortunately it is going to grow and change again once she hits puberty. Her ear drum is probably smaller than mine, only by a matter of fractions of millimeters maybe, but which frequencies are most effected by small changes? High ones. If you have ever heard “kidz bop” or recordings of nursery rhymes, they are usually kids singing, or some adult singing in an obnoxious voice. There is a mechanical reason that this is what you want in children’s music. While I can’t say what frequencies kids respond to better, but a smaller ear drum will have more resonances in higher frequencies than a slightly larger one. We are talking very small, nearly unnoticeable differences, but all these parts in our ear change the way our “brain averaged” sound is perceived in our brain. When you hear it when you are older it just sounds annoying.

In reality this is a bad example, because the real reason kids like kids songs is because of their simplicity, then as we get older we desire more complexity (most of us anyway). The point I’m making is that the “brain averaged” sound changed from person to person, and even throughout your life, just based on the mechanical response of your ear.

The brain doesn’t speak mechanical vibration though. It needs electric impulses to form a thought about it.  Say we have two identical twins. We will assume that their ears are exactly the same shape and therefore the mechanical response is exactly the same. Even in these cases, their tastes can and will differ. Now we are at the part that is hard to understand. After the sound leaves the ear and goes to the brain, there is still a difference from person to person on how they will perceive it, even if they have the same ears.

Back to the twins example, the sound enters the brain of each twin with the same “brain averaged” response to the sound. One twin thinks the sound is awful while the other enjoys it. This is due to psychological phenomenon. Since this is a metal blog, the song that the twins are hearing is metal. One twin, while physically identical to the other, had a harder life. He got made fun of at school for something he did one time and the classmates never let him live it down. The other one socially integrates just fine. Fast forward 15 years, they are just finishing up puberty and beginning to understand themselves as an individual. The twin who got along with everyone just fine, well he is probably going to like what the majority of people do. He is going to respond well to songs that are about having a good time, social situations, and disrespecting women. After all what more can he ask for? He responds to the feelings he is accustomed to feeling the most. Since he has always had a good time, always been accepted by everyone, he is going to like music about having a good time that is accepted by everyone.

What about the other twin, the one who gets bullied? Well life is a little different for him. He has few friends, and the friends he does have are weirdo’s who he can’t really relate with. He often feels angry,  hurt, isolated, even afraid at times. This twin hears a song about having a good time in social situations, well he isn’t going to like that very much is he? Sure he wants to have a good time, but to him he can’t relate with the feelings that the music is trying to portray. He is going to respond to what he knows, those negative feelings.

I just took a lot of words to explain that people like music because of the way it makes them feel. When I ask people “what do you like about it” and they say “because I like the way it makes me feel,” I have no arguments to make. Obviously I’m looking for a little more insight into the persons mind as to how they perceive the music and why, but the truth is this is all there is to say. Music DOES make us feel things, whether we like it or not. All it is, is a series of mechanical vibrations going through an extravagant unit conversion into the “brain averaged” sound, but when it gets there our brain reacts to it. The brain can have a number of different reactions, all amounting to “I like this” or “I don’t like this” even if we can’t explain what it is that we like about it. Every person not only physically interprets sound differently (which I think is more a minor factor in the equation overall), but based on their feelings, their past experiences, what makes them who they are, the brain will have a different response to it, for every single person on earth. It is my belief that no two people have EVER heard a sound exactly the same way another has. The only person who can hear what you hear, is you.

So tell me
Why do you like it?

 

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