SIMPLE SOUND

Sound depends on three things: a vibrating source to create the sound waves, a medium (such as air) to carry the waves, and a receiver to hear them. Soudwaves can't travel through a vacuum.

Comparing sound waves to water is a good way to explain the basic concept of how sound travels. However, keep in mind that just as water ripples from a pebble look different than ripples from a large rock, sound waves also vary in size.

Suppose someone hits a trash-can lid with a drum stick, the lid will rapidly bend outward and inward in the air. This movement pushes and pulls the air next to the surface of the metal creating a sound wave. The wave travels outward from the trash-can lid, becoming weaker and weaker until it dies away. However, if the trash-can lid is struck with a heavy mallet, the sound waves will cause more movement and will be heard a further distance away.

Sound waves travel at a constant speed, no matter how loud or soft the sound. Temperature does affect their speed. At room temperature (70 degrees Fahrenheit) sound travels in air at 1,129 feet per second. With each rise of one degree, the speed increases by more than one foot a second. Some mediums are better at conducting sound than others. Like all gasses, air is a poor medium for sound waves. Liquids, such as water, are better, and rigid, solid substances, such as iron and stone, are even better, while rubber, cork, and cotton are some examples of poor conductors.

It is for that reason that STOMP doesn't use many of these substances to create its sounds. With "rubber pipes" STOMP utilizes the medium of rubber to create a very musical and soft sound, which contrasts to the metallic clashes of the trash cans or even the Zippo lighters. Some sounds are high and others are low, some are loud and others are barely audible, some are pleasant while others are harsh. The three basic properties of any pure sound are its pitch, intensity and quality.

Pitch is the rate at which the vibrations are produced. The higher the frequency of the tone, the higher the pitch.

Intensity depends on the strength, or amplitude, of the vibrations producing the sound. If a piano string is struck forcefully the string swings back and forth in a wider arc. The stronger vibration then produces a louder tone since stronger vibrations compress the molecules of the air more forcefully and gives them greater energy, which is interpreted by our ears as a louder sound.

Quality, or timbre, of a sound determines whether a sound is pleasant to hear. The melodic sound of the rubber pipes may have a pleasant quality, whereas the crashing of the oil drums may be unpleasant.

Each item creates a sound that is comprised of a basic frequency and a range of softer, higher frequencies, called overtones. The quality of the sound is distinguished by the range of frequencies, or harmonics, contained in the sound and its accompanying overtones.

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MUSIC: CONTROLLED MUSIC

To produce the patterns of sound we call music, it is necessary to control or limit the frequency and intensity of the sound waves. Different types of musical instruments do this in different ways. Wind instruments such as the organ, flute and trumpet do this by means of a property of sound known as resonance: the process by which sound vibrations build up.

Resonance reinforces sound in much the same way that a mechanical movement can be reinforced. Suppose you are pushing a swing. To get it to swing high, you must push it at the exact tempo of its natural frequency of motion. A slight force applied each time the swing reaches its highest point will soon build up a wide movement.

An example from acoustics would be the rattling of a window when a low-flying airplane passes overhead. If the natural frequency of vibration of the windowpane happens to be the same as one of the frequencies that make up the noise of the plane's engines, the window will reinforce (resonate) the sound. In the same way, a certain note on the piano may make a chandelier tinkle, and a singer's high note may cause a glass to vibrate to the point of breaking.

EXPLORATION 1
Pinch together the prongs of a dinner fork so that they are set into vibration. The sound is very faint. Now press the end of the handle firmly down against the top of a hard table. The sound at once becomes remarkably loud.

In a closed organ pipe (Figure 1a, below), a jet of air blowing just inside the sharp lip of the pipe builds up extra pressure there. This region of compression travels down the pipe at the speed of sound and is reflected back. When it reaches the open end once more, the compression pushes the airjet out of the tube. The pressure is relieved, the airjet comes back into the tube again, and everything repeats. The length of the pipe regulates the frequency of vibration of the air jet and thereby the frequency (pitch) of the note.

EXPLORATION 2
The simplest of all wind instruments is a tube or tall bottle that you can blow by directing a stream of air across the open end, just inside the far edge. Try bottles of different length and observe that the longer ones give deeper notes.

An open organ pipe, as well as most brass and woodwind instruments, is open at the far end. The way sound is reflected from the end is changed by this. It is the length of the pipe that controls the pitch of the tone (Figure 1b). Other wind instruments use flexible reeds or the lips of the player instead of an air jet, and some, like the cornet and tuba, shunt air through different lengths of tubing.

A vibrating body may also transmit its movement to another body with a large surface to magnify the sound by setting more air in motion. The sounding board of a piano, the body of a violin, and the diaphragm of a loudspeaker are all examples of forced vibrations: they amplify all frequencies transmitted to them.

Bowing, plucking, or striking the string at different points in its length creates different frequencies of vibration. The thickness of the string and the point at which it is stopped or struck are ways of controlling the frequency of the sound produced.

EXPLORATION 3
Check some of the facts about vibrating strings by making a simple one stringed guitar. Stretch a rubber band around a long pan, such as a baking tin. Use a stick or a pencil as a "bridge." With the bridge absent, pluck the string and note the pitch of its tone. Then insert the bridge under the center of the string, pluck either half, and notice that the tone produced is the octave of the first one.

Placing the bridge at the quarter point will give the next octave. Also try to produce the familiar do-mi-sol-do of the major chord by using the "open" string then placing the bridge at distances 1/5, 1/3 and 1/2 from the left end, each time plucking the right hand portion of the string. Another fact you can check is that tightening a string raises its pitch.

Percussion instruments such as drums and bells create tones by the striking of bars, plates, stretched skins, or some other material that give their motion to the surrounding air. The thickness of the material, its density, and so on determine its rate of vibration and therefore the pitch of the sound.

Different types of instruments also produce different qualities of sound. These have to do with harmonics, also called overtones, which are vibrations at different strengths whitin the same tone. Electrical devices called harmonic analyzers can analyze the complex waveforms produced by different sources (Figure 2) and modern electronics can be made to reproduce (synthesize) these natural waveforms.

Figure 2

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NOISE VS. SOUND

The simplest definition of noise is "unwanted sound." However, the question arises: unwanted by whom? The teenager walking down the street with his suitcase-sized stereo likes what he hears, but others may not. Classical music from a car radio may be noise to people on the street, but the driver of the car wouldn't feel that way. It is generally accepted that a person's perception of noise depends on the characteristics of the sound; its loudness, frequency, and whether it is customary or unusual. To some extent, an individual's age, emotional makeup, tastes, beliefs and other factors determines the degree of annoyance with noise. The newspaper skit in STOMP addresses the issue of noise verses sound. In this section, each of the performers is annoyed by the noise of others rustling their newspapers. However, the audience perceives the very same rustling noise as music and enjoys its sound.

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ALL ABOUT RHYTHM

For Luke Cresswell and Steve McNicholas, the founders of STOMP, rhythm is the music of life. They hear rhythms in everything. As Steve says, "You see people walking to work. Some walk slowly because they are depressed and some walk quickly because they are in a good mood. That's all rhythm. People running up and down steps, people flicking a newspaper when they read it.... I think rhythm is knocking around everywhere." STOMP opens up people's minds and encourages audiences to recognize the rhythms of their lives. People aren't the only ones capable of creating rhythms, inanimate objects also create rhythm. For example, machinery like trains or natural things such as the wind or sea all make sounds and rhythms. Rhythmic contrasts between man-made and natural sounds describe their differences.

Think about an old steam train, which works on the basis of pistons. The sound of pistons is regular, consistent and invariant. Its regularity is important for the train to maintain a constant speed. If the rhythmic pace accelerates so does the train. The rhythm controls the train and the train controls the rhythm.

Natural occurrences, like wind, rain and the sea are not controlled. This is reflected in their rhythms which are irregular, inconsistent and unpredictable. Rhythms do not only describe mood and attitude, they also indicate form and motion.

Many people describe STOMP as "pure rhythm." Is this true, can it be termed music? When looking at classical or popular music, rhythm is an intrinsic and inseparable component. In the opening bars of Mozart's Requiem or Michael Jackson's Thriller, the rhythm is every bit as important as lyrics, melody and intensity.

In STOMP, the balance between these elements has been off-set, making rhythm the most important factor. However, in elevating rhythm the other elements have not been discarded. The combination of intensity, melody and tone with rhythm gives form to the pieces. For example, the show opens with one person, one broom and a simple rhythm. As more performers enter, the rhythms get more complex and the intensity crescendos until it reaches a climax, and then diminishes to finish off the piece. This is the basic form of any piece of music. A clear example of different pitches being used is "Pipes", where the flexible, hollow pipes of differing lengths and size create an eerie sort of melody.

Perhaps the most important alternative element to rhythm is tone. For example, STOMP uses the loud clashing tone of the drums in contrast to the crisp rustle of the paper-bag. The smooth swish of the brooms or the quiet clicking of the Zippo lighters are differences in tone which gives texture to the rhythms.

Similarly, the different tones which are made by a saxophone, trumpet and bass played together create the sound of a jazz band. STOMP has all the elements of traditional music, including melody, but the balance between the different components has been altered to create a style of music that is anything but traditional.

Music and sound exist even if we do not notice. STOMP has shown us that the strangest things can be musical. Think of birds calling in the fields, rain on a tin roof, a semi or large truck passing cars, or you and your friends at the mall. Sounds are an integral part of our lives and rhythm is an inseparable part of sound.

There truly is a rhythm to life. Just listen and you'll hear it, too.

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CREDITS

Written and compiled by
Karalee Dawn, Bronte Flecker,
Karl Baudendistel, John Piccirillo
Karen Greco and David W. Caldwell

Designed by David W. Caldwell
Assisted by Karalee Dawn

Photographs courtesy of
Steve McNicholas and Lois Greenfield

General Management
Richard Frankel Productions
Marc Routh David W. Caldwell

General Press Representative
Boneau, Bryan/Brown
Chris Boneau Jackie Green

Tour Press Representative
TMG Marketing & Publicity
Tanya Grubich Anne Rippey