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The Physics, Biology, and Psychology behind Music

Megan Herring

Published on May 26, 2013

Abstract

Swaying back and forth in a sweaty mosh pit, fist pumping in the air to the bass drum, and voices screaming out lyrics; a concert can be a thrilling experience. Seemingly far away from academics, rock stars rule crowds with glittering guitars and windmills. But where does music come from? While music may be enhanced by large crowds of people and cultural trends, in essence, music is explained by scientific phenomena. In fact, art through science happens everyday. As the laws of physics create music, our anatomy and brain function allow us to hear and process the music. The question then becomes how can something as simple as a guitar string conjure up such emotions or make such interesting sounds?

Physics and Music, what's the big deal?

Why is physics so important to music? Many rock and roll stars never even attend college, let alone give a single glance to a textbook (with the exception of Queen's Dr. Brian May, of course). So why care? First, it is important to consider what actually makes sound.

Sound consists of waves, which are described as disturbances caused by energy that moves through a medium. In the case of music, that medium happens to be the air around us. Sound in particular is a mechanical wave, meaning that the wave is passed along through particle interaction [1]. Tuning forks, for example, clearly illustrate this concept. When a tuning fork is hit with a rubber mallet, a disturbance is created through vibrations. Those vibrations pass through the air when particles bounce off of each other, thereby creating a mechanical wave. These waves are also longitudinal. In other words, they flow in one direction parallel to the direction from which the energy that caused the disturbance came. This concept can clearly be heard at work with speakers. When you tilt your ears towards a speaker, the sound becomes louder. Then, when you move back to your original position, the sound becomes softer because your ears are not directly facing the waves of the sound [2, 3].

Vibrations, as mentioned before, create sound waves. The speed at which an object oscillates (vibrates) is called the frequency, which is measured in Hertz or vibrations per seconds (1 vibration/s) [4]. In musical terms, frequency is commonly referred to as pitch. A high frequency causes a high pitch, a low frequency a low pitch. People who are musically trained, or have perfect pitch, are able to detect changes in frequency as minute as two Hertz. Pitches and frequencies are what determine octaves on the musical scale as well as thirds, fourths, and fifths, all of which can be heard in a wide variety of musical genres today [2]. There are also certain frequencies that sound very pleasant to the human ear when played together, creating harmonies and melodies that we attribute to different styles, whether it be a ninth chord in jazz or a power chord in a heavy metal tune.

A guitar demonstrates all of these factors flawlessly. When a guitarist plucks a string, that string vibrates at a certain frequency. The thicker the string, the less it vibrates, creating a lower frequency and thus a lower pitch. These vibrations create a sound wave that travels through the air by transferring energy from one particle of air to another. These waves travel parallel to the string, or the source of the vibration, and slowly dissipate as the sound waves travel further away from the source and the energy is slowly wasted through vibrating particles. Yet, if this is an electric guitar with an amplifier, the energy used to create the sound is greatly increased, and thus the sound wave travels much farther and is louder. The increased energy also increases the intensity of the sound which is calculated by dividing the amount of energy used by the area the sound travels; the further the sound goes, the less intense it gets.

A guitar string is a prime example of the physics behind music, but what about concert halls? Engineers create concert halls in ways that reflect sound waves in order to create the most acoustically enjoyable experience. Sound waves behave much like light waves in that they can be reflected like light on a mirror. Certain floors can create a dead sound or an echo when musical instruments are played there. Amplifiers, like the one used in the example above, increase intensity, which allows for sound to bounce off of the walls of a concert hall to create the best sound possible [5].

The Biology of Music

While sound waves can be explained by physics, how do human beings process those sound waves? An amazing biological feature attached to the sides of our head: the ear.

Ears, although seemingly simple, are complex structures that allow for humans to pick up frequencies between 20 and 20,000 Hz. Of course, if you've spent time at numerous concerts, love to play music too loud in the car, or think that ear protection is downright unattractive then you may not be able to hear this full range because of damage caused by sound.

So how does the ear actually function? The ear consists of three separate areas: the outer ear, the middle ear, and the inner ear. The outer ear is what is responsible for "catching" sound waves and is the only externally visible portion of the ear. Sound is then funneled to the middle ear by the ear canal. In the middle ear, the sound waves cause the eardrum to vibrate which then causes three bones called the hammer, anvil, and stirrup to be set into motion. The oscillation of these bones then transfers to the cochlea, which is part of the inner ear. The cochlea is filled with fluids and brittle hairs that pick up the vibrations of the middle ear. These vibrations are then read by the auditory nerve, which sends a signal to the brain. The brain registers this signal and processes the frequency of the sound wave that was heard.

When the eardrum vibrates too violently, it can cause hearing impairment. This tends to happen when sound has a high decibel rate, meaning that the volume is too loud, or has a high frequency. When the eardrum oscillates too much it can break off many of the brittle hairs within the cochlea that help to register sound. This breakage prevents the individual from hearing certain high or low pitches. When a person ages, they have been subjected to more experiences with sound and are susceptible to hearing loss due to this damage. As many a rocker has found out, too many amplified guitars in a small room could lead to major hearing loss down the road [6].

Psychology: Your Brain on Music

Listening to music is bad for hearing health and could drastically affect individuals later in life, but people do it anyway. Why? Research indicates that music may have a significant impact on certain areas of the brain.

Listening to and, to an even greater extent, playing music, affect most structures within the brain. The right side of the brain processes the feel and creativity of the music, while the left side logically informs what will come next or what finger to place on which fret in order to make a certain chord. It has been suggested by researchers at UCLA that listening to music stimulates certain neurons in the brain, which fire when a person is experiencing specific emotions. This seems obvious to the casual observer as certain songs are prone to make us sad, happy, or wound up. The same research also suggests that this is due to our neurons mirroring the performer of the music: those neurons responsible for auditory, linguistic, and physical activities all have the same root [7]. This is just a theory, but it would explain why emotional music has such an impact on humans in general.

While music affects everybody emotionally, it seems that everyone has different tastes. Research in psychology has suggested that the reason for this stems from memories. Music engages with many parts of the brain, but the most important part that it stimulates is the cerebellum. Located at the back of the brain, the cerebellum is in charge of emotion, language, and processing memory [8]. Growing up, certain memories caused pleasure, meaning that your body produced dopamine. Music has the ability to remind you of those memories and, when reminded, your body sends out another dose of dopamine. This also works the other way around for certain sounds that bring back bad memories. Music attracts on an emotional level because it can provide us with extreme pleasure [9]. People who have grown up listening to a certain genre will most likely adopt that genre as their favorite later on in life, or, if they were exposed to a certain role model who enjoyed a specific artist, an individual may start listening to that artist as well. Culture also affects popular music, though the nuances of that impact go beyond the scope of this paper. Let's just leave it at the fact that music is better enjoyed with a group. After all, we are gregarious creatures.

Works Cited

1. "Sound as a Longitudinal Wave." [Online]. Available: http://www.physicsclassroom.com/Class/sound/u11l1b.cfm. [Accessed: 05-Apr-2013].

2. G. L. Rogers, "Interdisciplinary Lessons in Musical Acoustics: The Science-Math-Music Connection," Music Educators Journal, vol. 91, no. 1, pp. 2530, Sep. 2004.

3. "Sound is a Mechanical Wave." [Online]. Available: http://www.physicsclassroom.com/Class/sound/u11l1a.cfm. [Accessed: 05-Apr-2013].

4. "Pitch and Frequency." [Online]. Available: http://www.physicsclassroom.com/Class/sound/u11l2a.cfm. [Accessed: 05-Apr-2013].

5. Intensity and the Decibel Scale." [Online]. Available: http://www.physicsclassroom.com/Class/sound/u11l2b.cfm. [Accessed: 05-Apr-2013].

6. "The Human Ear." [Online]. Available: http://www.physicsclassroom.com/Class/sound/u11l2d.cfm. [Accessed: 05-Apr-2013].

7. D. Byrne, "How Do Our Brains Process Music?," Smithsonian magazine. [Online]. Available: http://www.smithsonianmag.com/arts-culture/How-Do-Our-Brains-Process-Music-169360476.html. [Accessed: 06-Apr-2013].

8. "Parts of the Brain - Memory & the Brain - The Human Memory." [Online]. Available: http://www.human-memory.net/brain_parts.html. [Accessed: 05-Apr-2013].

9. V. D. Wolverton, "Book Reviews: 'This Is Your Brain on Music/The Science of a Human Obsession,' by Daniel J. Levitin," Choral Journal, vol. 49, no. 8, pp. 8891, Feb. 2009.

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