For an explanation, see the main splats page
The principles of sound
- Sound is made of vibrations. A musical note is a uniform vibration. Waves with a greater amplitude have more energy, which makes them sound louder.
- Every musical note or tone has in it harmonics or overtones which add to the richness of the sound, and producing the characteristics of different instruments.
- Sound vibrations may be seen with an oscilloscope. You can also make the vibrations of a string visible by using a very long, thick string or wire.
- Every object has a natural frequency at which it vibrates, which is known as its resonant frequency. When struck, it will vibrate at this frequency.
- Vibrations can be made in a variety of ways. Plucked strings and struck objects vibrate to make a tone, and resonance in a tube can make a tone.
- Tone and pitch are both aspects of the frequency of the note being heard. The tone is a single frequency, the pitch is a subjective perceived frequency.
- Sound can be observed and/or visualized in Chladni figures, made when a violin bow is rubbed on the edge of a steel plate scattered with fine sand.
- Sound can be reflected and refracted. Acoustics is basically the study of how sounds are changed in an environment as they reflect and refract in a space.
- Sound from a moving source that is moving towards or away, relative to the listener, appears to change frequency, due to the principles of the Doppler effect.
- Thunder is caused by air being heated along the lightning flash, causing an increase in pressure. The bang from more distant parts takes longer to arrive.
- Sonic booms are caused when an aircraft or other object travels faster than the speed of sound in the atmosphere at the level at which it is flying.
- Beats occur when two very similar waves move in and out of synchronization, either reinforcing each other or cancelling each other at different times.
- The bang of a gun, a firework or a handclap are all caused by the sudden release of gas under pressure. The bang is the pressure wave reaching our ears.
- Sound travels through all materials as compressions and rarefactions, although it travels through some materials better (and sometimes faster) than others.
- Sound is most easily considered as a wave, but may also be thought of as a cyclic variation in pressure. The model we use does not change the sound's nature.
- In 1640, Marin Mersenne established a reasonable estimate of the speed of sound in air, which he set at 320 metres per second. The usual value today is 330 m/s.
- The velocity of sound can be measured and shown to vary with the transmission medium and also travelling faster when the temperature of the medium increases.
- The intensity of sound can be measured in decibels. Sound above a certain intensity can cause temporary damage to the delicate parts of the ears, or deafness.
This file is http://members.ozemail.com.au/~macinnis/scifun/, first created on February 20, 2009. Last recorded revision (well I get lazy and forget sometimes!) was on February 20, 2009.
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