The video “Physics of Musical Instruments” discusses the physics of sound and how musical instruments work to produce music. It is the disturbance of the air that creates the sound wave by moving the air particles. The sound waves are then received by the ears and interpreted by the brain. The properties of the air determine the speed with which sound propagates from one location to another. Music is the repetitive shaking of the air, so that it results in a repetitive, periodic compression of the air particles. This creates regular areas of high particle density and low particle density areas. These are the physics underlying the sound produced by every musical instrument.

Once this principle is established, the characteristics of the individual sound wave are described. The wavelength tells the distance between the waves. The frequency is the number of wave cycles per second. The human hearing range is between 20 Hz to 20,000 Hz. The speed of sound is 343 meters per second. In music, one is interested in the production of repetitive sounds at various frequencies and wavelengths.

High frequency sounds are perceived as having a higher pitch than lower frequency sounds. One music octave is represented a doubling of the frequency. The musical range used by humans covers majority of the sound that is possible for the human ear to perceive. A musical fifth is 1 ½ times the frequency of the bottom note. Other intervals are also produced, such as a third, and fourth.

Various objects are used to shake the air and produce waves at a certain frequency. These include strings, drumheads, pendulums, and the walls of the instruments. The properties of the object help to determine its characteristic resonant frequencies. The resonant frequencies will determine the nodes and antinodes of the wave as it travels along the string. The nodes will be located on each end, and the others will divide the string evenly. The first resonance of the string is the fundamental resonance of the string. To raise the pitch of the string, one can either cut the length of the string in have or vibrate it faster. One can also change the thickness of a string to speed up and slow down the velocity. Increasing the tension on the string will also increase the velocity and pitch of the string. One can change the length, size, and tension on the string to change the pitch.

The timbre of the instrument gives it a distinctive characteristic. For instance, a piano and a violin can be distinguished easily. The shape of each wave is different and can be complicated. To determine the pitch, one has to look at the frequency of the overall wave. The complexity of the instrument comes by the addition of multiple wavelengths. Each complex wave can be deconstructed into its individual components. The individual resonant frequencies are determined by the individual characteristics of the instrument. Instruments do not produce a single, pure, sound wave, but produce many of them at the same time. These are called the harmonics of the instrument.

The combinations of the harmonics of an instrument produce its distinctive timbre. The harmonics of the instruments have a musical relationship to each other. The resonances of the strings correspond to the intervals on the musical scale, for the most part. Anharmonic instruments, such as a drum, make a percussive sound, with little pitch associated with it. The waves of an anharmonic instruments the frequencies are related to each other but do not follow the same regular pattern as a harmonic instrument. Some instruments, such as a bell, are between an anharmonic and harmonic instrument. They are harmonic in the lower frequencies and become anharmonic in the higher frequencies. The construction of instrument influences the sound that they create.