SOUND WAVES 1 WHAT IS SOUND WAVES Sound

SOUND WAVES

1. WHAT IS SOUND WAVES? Sound waves are mechanical energy and exist as variations of pressure in a medium such as air. They are created by the vibration of an object, which causes the air surrounding it to vibrate. The vibrating air then causes the human eardrum to vibrate, which the brain interprets as sound.

2. PROPERTIES OF SOUND WAVES There are three important properties of sound waves. These are: a. Wavelength b. Amplitude c. Frequency

Wavelength: The distance between any point on a wave and the equivalent point on the next phase. Literally, the length of the wave.

Amplitude: The strength or power of a wave signal. The "height" of a wave when viewed as a graph. Higher amplitudes are interpreted as a higher volume, hence the name "amplifier" for a device which increases amplitude.

Frequency: The number of times the wavelength occurs in one second. Measured in kilohertz (Khz), or cycles per second. The faster the sound source vibrates, the higher the frequency. Higher frequencies are interpreted as a higher pitch. For example, when you sing in a high-pitched voice you are forcing your vocal chords to vibrate quickly.

COMPLETE ILLUSTRATION OF SOUND WAVES: The compressions, in which particles are crowded together, appear as upward curves in the line. The rarefactions, in which particles are spread apart, appear as downward curves in the line.

3. HOW IS SOUND CREATED? Sound is produced when the air is disturbed in some way, for example by a vibrating object. A speaker cone can serve as a good illustration. It may be possible to see the movement of a bass speaker cone, providing it is producing very low frequency sound. As the cone moves forward the air immediately in front is compressed causing a slight increase in air pressure, it then moves back past its rest position and causes a reduction in the air pressure (rarefaction).

EXPLANATION:

• Sound waves which are exactly in phase add together to produce a stronger wave. • Sound waves which are exactly inverted, or 180 degrees out of phase, cancel each other out and produce silence. This is how many noise-cancellation devices work. • Sound waves which have varying phase relationships produce differing sound effects.

USES OF SOUND WAVES • When sound strikes soft materials, much of the sound is absorbed. A sound insulator is a material that absorbs most of the energy of sound waves. • Geologists use their knowledge of rocks to help them locate oil resevoirs. • Earthquakes can be tracked and their waves understood once the geologist understands how the earthquake waves travel through different kinds of rocks and magma. • Ocean exploration • Marine mammals and bats use sonar location • The military uses sonar in submarines and in planes