How Do Sound Waves Produce Music?

What happens?

When someone plays the piano, those notes or hits on the piano strings cause sound waves. These disturbances in air pressure can travel outward as vibrations. Only when the vibrations hit a receiver or hearing source, like an ear, for example, will these vibrations register as sound or music. A piano or even a person can be what is known as a "medium." In physics, the medium is really considered a material substance--the way the music travels will have a lot to do with what type of substance it chooses to travel through. Music will sound different in water as opposed to air, for example. The medium can be a someone or something which has to act on an object (the person can be an "object," as well), for music to happen. A generating source, that person or instrument, has make a vibration or cause a wave of high pressure to disburse. Music can also be thought of as a way of formally intepreting sound, like a "sine wave," for example.

Sound Waves

Just like ripples in the water, waves move and look just the same way. The only thing is, people cannot see this when it happens. Sound waves are created when an pressure equilibrium position, a person or piano, creates a disturbance. A disturbance is sent or "propagated," from one area to another. The wave travels up and down, causing crests and troughs along a wavelength. Put simply, to make a sound, you have to create a circumstance in which air molecules move back and forth. You can make music by using sound acoustics (or vibrations) in an enclosed space, like a piano or guitar. The frequency with which those sounds travel can determine pitch--auditory elements like loudness, softness or even tone. A good way to visualize this is to imagine a person dropping a rock in a body of water. The rock sends waves outward until they disappear. This is similar to what happens when you try to listen to music from too far away. The sound waves or music, in this circumstance, literally dissipate into nothingness.

Music waves are not radio waves...

The type of waves created by music are generally not considered electromagnetic waves--they are physical waves. Physical waves, unlike radio waves, for example, need something to create it, and then it needs something to travel through. Radio waves travel whether they have a medium or not. Both are vehicles to which energy is transferred from one place to another.

Hearing and Music

Certain frequencies are very readily heard by the human ear, others are not. Threshold of hearing is a physics concept that has a lot to do with music, sound and human hearing. The term "Absolute Threshold of Hearing" (ATH), generally refers to the lowest frequency level a person is able to hear under "normal" circumstances--listening to a bird close by, for example. This point is between about 2000 and 3000 hertz (Hz) at about -5 decibels (dB). A decibel has to do with the intensity of a given portion of sound--how loud it might be. If you increase the decibel level, you will reach what is known as "threshold of pain." In contrast to ATH, threshold of pain is reached at approximately 20, 000 dB.

Resources

• Read this Article in Spanish
• Imperial College: Theoretical Physics, Music and Sound
• Physics of Music-Notes
• Music v. Physics