Physics Of Percussion
Physics Of Percussion
The Physics of Percussion Instruments
All the time during your life, everyday, somewhere, you will hear some sort of percussion. Whether it is the music on a commercial, the music on the radio, or you might catch yourself tapping on your desk. Percussion however is much more than just drumming, tapping, or banging. Percussion is yet another form of physical science. Using some sort of method of beating a surface, the surface is struck thus causing a vibration. The vibration will cause a sound depending on the timbre of the surface.
There are 3 types of pitches created by percussion instruments: Single Indefinite Pitch, Multiple Indefinite Pitch, and Variable Pitch.
"Single Indefinite Pitch- The majority of percussion instruments are in this category. When these instruments. The story of percussion is vibrations. When a drum is hit, it makes a vibration. This is what makes a sound. To make a louder, or more intense sound, a drummer hits the drum with more force making a larger vibration. This is the basic concept of single indefinite instruments. You strike it and it makes a sound.
This applies to more than just drums, however. Besides drums such as snare drums and base drums, triangles, tambourines, maracas and other "auxiliary percussion" have their home here. Instruments such as the maracas and tambourines consist of many vibrating objects vibrating simultaneously like the beads in the maracas and the disks on the tambourine. " (http://www.kent.wednet.edu/staff/trobinso/physicspages/po2000/jones/)
"Multiple Indefinite Pitch- Multiple indefinite instruments are basically the same as single indefinite pitch instruments. They have different components to the instrument with different pitches. Sometimes these are tuned to certain pitches. Most of these are "mallet" instruments such as xylophone, vibraphone, marimba, and glockenspiel. They consist of bars of instruments that emit certain wavelengths, and therefore certain frequencies. The frequency determines the pitch. The instruments are designed to be similar to piano, each bar representing a piano key. The size of the bar determines the frequency and instrument makers shape the size of the bars until the different pitches match a piano's pitch. This makes the harmonies that we can hear.
Other instruments in this category are a bunch Sing Indefinite Pitches compiled together. Multiple toms, a type of drum, make a variety of pitches to produce. Large groups of cymbals also have the same effect. A drum set could be put in this category. This allows for a larger variety of sound." (http://www.kent.wednet.edu/staff/trobinso/physicspages/po2000/jones/)
"Variable Pitch- Some of the most interesting instruments to hear are the variable pitch instruments. The biggest physics concept of these is tension. Tension decides the frequency an object vibrates. The bigger the tension, the faster vibrations and the higher the pitch. A common example of this are the kettle drums, or the timpani. The timpani are large drums hit with mallets to produce a tuned pitch. There are pedals on the bottom of the drums controlling the sound. The pedals can decrease or increase the tension in the head of the drum, the part the drummer strikes. With and increased tension, the pitch goes, and with a lower tension, the pitch goes lower. Then the drums are tuned. "
The actual sound of a drum is vibrations of the air inside the drum. "Percussion instruments are basically all about vibration and resonance. In a drum set for example, there is a cylinder which is the body of the drum with a piece of taut material at the top known as the drum head. There may also be another head at the bottom of the drum. When you strike the drum, the head deforms, but the tension causes it to snap back into place, vibrating the air inside the drum. The body of the drum also begins to resonate, as well as the head on the bottom of the drum if it is there, causing a loud sound to come from the drum." (http://www.mrfizzix.com/instruments/percussion.html)
As any type of physical science, there are equations that can be used for figuring things out. "For xylophones, marimbas, or other instruments using vibrating plates or rods supported in the same way, you would use the equation:
For drums you would use the equation:
In these equations L is the length of the bar, v is the velocity of sound in the object, k is a constant that changes depending on the object:
.025d for round rods with a diameter d.
.289t for rectangular bars of thickness t.
T is the tension of the drumhead in Newtons, F is the tension of the drumhead per unit of circumference of the drumhead in Newtons/meter, D is the diameter of the drumhead, and μ is the area density of the drumhead measured in kg/m2 " (http://www.mrfizzix.com/instruments/percussion.html)
Percussionists around the world have put years into making the patterns and rhythms into what we call music. But little do most percussionists around the world realize the amount of physical science involved in the structure of their instruments. Every single type of percussion instrument from bongos to maracas. The world of physical science is opening up new ways of exploring the science behind percussion. With new technological advances such as Vibrational Holography, scientists can actually record images of the sound waves of percussion instruments. These new discoveries can be used to perhaps better the sound of percussion instruments. Or perhaps they can create new instruments with new and exciting sounds never before heard by man.