Sound pressure waves are created when matter is vibrated.

A discussion of longitudinal wave lengths, compression and rarefaction.

A sound wave vibrates at a certain frequency or pitch, measured in Hertz.

Sound travels at different speeds, depending on the medium and the temperature.

The Doppler Effect explains why the pitch appears to increase as a sound moves toward you, then decrease as the sound passes you.

Sound has the properties of intensity which is measured in decibels.

Complex wave forms will be created when two sound waves interact, causing interference.

Beat frequencies occur when two sounds with very close frequencies are made at the same time.

Binaural beat frequencies can be used in sound therapy to give the illusion of hearing a lower frequency.

All objects have a natural frequency, or a group of frequencies, at which they will vibrate. Some objects have only one, while others have a mode of natural frequencies. Resonance is an induced vibration in an object.

Resonant quality, or Q, is the tendency of the object to continue vibrating or ringing.

It is possible to cause an object to vibrate without touching it by the process of forced vibration.

Entrainment is the automatic synchronization of two vibrating objects which have the same natural frequency.

When objects are disturbed, they can vibrate in one or multiple mode silmutaneously.

Standing waves stay in one constant position.

If a frequency is out of range, a frequency of a different octave can cause the same effect.

Psychoacoustics is the study of how we hear. The literal sound waves are interpreted in different ways before our brain hears them

Watch a video of the Tacoma Narrows Bridge, or Galloping Gertie, collapsing, just four months after it was completed.

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