1. Sound Sound is a form of energy that spreads out through a medium.

2.  The origin of sound in musical instruments begins with vibrating strings, reeds and columns of air. The Origin of Sound  All sounds originate in the vibrations of material objects  The origin of sound in human voice begins with vibrating vocal chords.  These vibrations stimulate the vibration of something larger or more massive.

3.  As a source of sound vibrates, a series of compressions and rarefactions travels outward from the source.  Remember, it is not the particles in the medium that travel, but rather a pulse of energy that travels.  Sound travels at about 330 meters/second in air, depending on the temperature. Sound in Air

4.  Sound travels in solids, liquids and gases.  The speed of sound differs in various media.  Sound cannot travel in a vacuum. Sound in Other Media

5.  The speed of sound in a gas depends on the temperature and the mass of the particles in the gas.  Increased temperatures increase the speed slightly.  Lighter particles transmit sound more quickly.  The speed of sound in a material depends on its elasticity.  Sound travels 15 times faster in steel than in air, and about four times faster in water than in air. Speed of Sound

6.  Sound Intensity is measurable by instruments in decibels.  Loudness is related to intensity but it differs from person to person.  Each increase of 10 dB in an increase in intensity by a factor of 10.  Hearing damage begins at 85 dB. Loudness

7.  Objects composed of elastic material, when disturbed, each vibrate at their own special set of frequencies.  Natural Frequency depends on the elasticity and shape of the object.  A Natural Frequency is one at which minimum energy is required to produce forced vibrations and the least amount of energy is required to continue this vibration. Natural Frequency

8.  Sounding boards are an important part of all stringed musical instruments because they are forced into vibration and produce the sound.  A forced vibration occurs when an object is made to vibrate by another vibrating object that is nearby.  Examples of sounding boards are the wooden body of an acoustical guitar, the body of a piano and your lungs and throat. Forced Vibration

9.  An object resonates when there is a force to pull it back to its starting position and enough energy to keep it vibrating.  When two tuning forks are adjusted to the same frequency, striking one fork sets the other fork into vibration.  The Tacoma Narrows Bridge collapse was caused by resonance. Resonance

10.  Constructive Interference increases sound while Destructive Interference decreases or cancels sound.  Constructive Interference occurs when the crests of one wave overlap the crests of another wave.  Destructive Interference occurs when the crests of one wave overlap the troughs of another wave.  Destructive Interference is used in Antinoise Technology. Interference

11.  When two tones of slightly different frequency are sounded together, a regular fluctuation in the loudness of the combined sounds is heard.  This periodic variation in the loudness of the sound is called beats.  To tune a piano, a piano tuner listens for beats produced between a standard tuning fork and a particular string on the piano. The beats disappear when the frequencies are identical. Beats