Beautiful Music and the Laws of Physics

by Rebecca Guerreso, AP Physics 1 Student

Ludwig van Beethoven once proclaimed, “Music is … A higher revelation than all Wisdom & Philosophy.” Music plays an important role in many people’s lives, yet few know that the basis of music and its sound derive from the laws of physics. Upon hearing a stirring piano solo, one may wonder what is occurring inside the piano that results in such a beautiful sound; the mysteries of sound within a piano originate from basic physics principles. Physics phenomenon regarding waves and oscillations result in the piano creating music.

Understanding the cause of the diverse sounds a piano produces, requires knowledge of the different parts inside the instrument. When a key is pressed on the piano, a sound is heard; when the key is pressed with a larger amount of force, the sound becomes louder. This sound and its amplitude are caused by four major components of the piano: the hammer, the damper, strings, and the soundboard. Every key has a damper, hammer, and either one, two, or three strings. Each of these parts has a different function; the damper stops the string from vibrating to ensure that when a key is pressed, only that key makes a sound. The hammer strikes the string, resulting in vibrations. The soundboard amplifies the string’s vibrations to make the sound louder. When a key is pressed, the damper is released so that the string can make a sound, the hammer strikes the string, and the string vibrates to make a sound.

A typical piano contains eighty-eight keys and has a range of seven different octaves. Starting from the right side of the piano, the first key has the highest pitch, and the pitch of each key after it decreases. The properties of the string for each key determine the pitch that the key will produce. Physics principles have determined that a longer string results in a lower pitch because the fundamental frequency is equal to the quotient of the velocity and two times the length, f = v/(2L). Inside the piano, the strings increase in length for keys with lower pitches, but if only the length were changed for each string, then the strings would exceed the height of the piano. Therefore, to lower a pitch of a key, the length is increased along with the diameter of the string. This concept holds true for all keys to the right of middle C; the keys to the left of middle C must be adjusted differently. If the diameter and length continued to increase, the string would not be able to vibrate regularly after a certain point, which would result in the production of an irregular sound. The keys to the left of middle C have a very low pitch; to accommodate this low pitch, the normal steel wires are wound with a copper wire. By winding the strings together, the total mass of the string increases, allowing the string to vibrate properly because if the mass is increased then the frequency of the string decreases. These physics principles result in octaves on musical instruments; physics has proven that doubling the length of the string decreases the resulting sound by an octave.

Typically, the frequency of each string on a piano ranges from sixteen hertz to seven thousand and nine hundred hertz, while wavelength varies from four centimeters to two thousand and one hundred centimeters. The ranges in frequencies and wavelengths cause each key to produce a different sound. A piano contains seven octaves and these seven octaves repeat throughout the eighty-eight keys on the piano (first key on far left is A; last key on far right is C). Each note on the piano has a fundamental frequency; to increase the note by one octave, the fundamental frequency must be doubled; to increase the note by two octaves, the fundamental frequency must be quadrupled (or the first level frequency must be doubled). The changed frequency creates different tones for each note.

Another factor that affects the piano’s sound are the three pedals. On a standard upright piano, the pedal farthest to the right is called the damper pedal, and is the most commonly used pedal. This pedal allows the notes to be played much more smoothly. When the damper pedal is pressed, the dampers are released from the strings. Consequently, when a note is played all the strings vibrate since there are no dampers to inhibit vibrations. The celeste pedal is the middle pedal; it drops a felt pad onto the tops of the strings in order to lower the amount of vibrations on the string, and in effect, make the sound much quieter. The pedal to the far left is the una corda pedal; it shifts the hammers so that it strikes fewer strings than usual, creating a softer sound because there are less vibrations.

The piano and the sounds it produces utilize many physics principles. The strings within the piano operate at different frequencies, which result in different wavelengths; this is why the piano has the ability to produce such a vast range of notes. Pianos go “out of tune,” meaning the keys produce incorrect sounds, throughout the year because the temperature fluctuates, which slightly changes the speed of sound in air. The sounds the piano creates is a language that everybody in the world can understand—sounds created by manipulating laws of physics. Henry Wadsworth Longfellow once marveled, “Music is the universal language of mankind,”and I could add physics makes music possible.

Works Cited

Joyner, Lauren, Erika Littman, Emily Massey, and Johanna Robertson. “Piano Physics.” String Vibration. N.p., 2009. Web. 09 May 2016.

Rack, C. Mckinney And Nsf. “Physics of the Piano.” Physics of the Piano N Giordano — Purdue University (n.d.): n. pag. Web. 9 May 2016.

Suits, B. H. “Frequencies of Musical Notes, A4 = 440 Hz.” Frequencies of Musical Notes, A4 = 440 Hz. Michigan Technolgical University, 1998. Web. 09 May 2016.

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Cochlear Implants: applying physics to improve hearing

by Kate Williams AP Physics 1 Student

Most Americans who have the ability to hear cannot fathom the lifestyle changes that come with deafness or profound hearing loss. In the United States, twelve thousand babies are born partially or completely deaf every year. Conservative ways to support deafness are Sign Language, mouth reading, or just living life in complete silence. However, throughout the past few years, physics has allowed cochlear implants to become the first medical device used to replace a human sense.

Although cochlear implants have not been around for a very long time, physicists have been trying to invent a hearing device since the early 1800s. Physicist Alessandro Volta conducted an experiment in which he connected a battery to electrodes in his ear. Through this experiment, Volta heard “unpleasant noises” and started the phenomenon of artificial hearing. The first surgically implanted cochlea was designed by Williams House and passed by the Food and Drug Administration in 1984.

To fully understand the brain’s reaction to sound, scientists use physics and the study of sound waves. There are two different types of waves: longitudinal and transverse. Transverse waves move perpendicularly to the direction of motion (as shown in the bottom part of the diagram). Longitudinal waves are the opposite; their waves move parallel with the direction of motion (as shown in the top portion of the diagram). Before creating the cochlear implant, physicists had to fully understand that sound is a longitudinal wave. Mechanical longitudinal waves must have a medium in which to travel. This characteristic of longitudinal waves is an important principle of the implant that allows sound to always go through the skin and into the device.

A cochlear implant is very different from a hearing aid. Hearing aids simply use vibrations to reach the remaining hair follicles in the cochlea. However, profoundly deaf people may not have much, if any, hairs left in the cochlea which is why the cochlear implant is surgically placed and is constructed of an inner and outer part. The inner part of the implant has a small soft wire that is placed within the ear and wrapped around the inside of the cochlea. The outer part of the implant is constructed of a microphone and a speech processor. The processor must be with the user at all times for the device to work; although, it may be taken off to shower or sleep. This processor is important because it picks up the nearby noises and converts them using a transmitter that is attached to a magnet that connects the internal and external parts of the device. The transmitter sends the signals to the internal part of the implant and then on to the brain.

Even though this discovery has helped thousands of deaf people, it does not come without risks. One major risk of the surgery is that it just may not work. The human ear is a very sensitive area and sometimes the surgery is not successful for certain people. A common misconception about cochlear implants is that the effect on hearing is immediate; however, six weeks are required for the surgical site to heal and be ready for the external portion of the implant. When the audiologist first attaches the outer piece, the recipient may not hear anything at first. It is the doctor’s job to then adjust the frequency of the implant until sound is heard. Once sound is heard, deaf people do not automatically understand what they are hearing. Most of the recipients have spent the majority of their lives using Sign Language and staying completely mute to outside sounds. So, although they hear sounds, the recipient must then go through long months of speech therapy to learn how to speak and understand spoken words. Many deaf adults who get the implant end up never wearing it because their brain has gotten so used to hearing no sounds that tiny noises such as the sound of a dishwasher or the starting of a car cause them a great disturbance. There is also the concern in the deaf community that cochlear implants are taking away the use of Sign Language and a culture that has been around for a very long time. In the deaf community, the appropriateness of cochlear implants is still a controversial issue, but in the physics community, it is a discovery worth sharing.

Works Cited

Cochlear Implant. Digital image. Kids Health. Nemours, n.d. Web. 20 Apr. 2016.

“Cochlear Implants.” Cochlear Implants. NIH Publications, 18 Aug. 2014. Web. 19 Apr. 2016.

“How It Works.” Hearing with a Cochlear Implant. N.p., n.d. Web. 22 Apr. 2016.

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