2. Sources of Sound  sound is a mechanical wave produced by vibrations that occur in a medium-- generally air  sound is a longitudinal wave

3. Transmitting Sound  in general, sound travels faster in solids and liquids than in gasses  in liquids and solids, the medium is more compressed allowing for the wave to travel faster and longer

4. Speed of Sound in air  temperature affects the speed of sound in air  the warmer the air, the faster sound travels  in room temperature air, sound travels at about 343 m/s

5. Loudness  loudness is a subjective physiological sensation  it is measured in decibels (dB)—after Alexander Graham Bell, the inventor of the telephone  the pain threshold for humans is generally around 130 dB  ear drum ruptures occur between 160 and 185 dB

7. Frequency and Wavelength  frequency and wavelength have an indirect relationship  as frequency increases, the wavelength decreases

8. Pitch and Frequency  pitch and frequency are directly related  the higher the frequency—the higher the pitch of the sound emitted  the lower the frequency—the lower the pitch of the sound emitted

9. The Doppler Effect  an apparent change in pitch due to the motion of a source of sound

10.  as a source of sound moves toward an observer, the wavelengths decrease in front of the source of sound resulting in an apparent higher frequency

11.  as a source of sound moves away from an observer, the wavelengths increase behind the source of sound resulting in an apparent lower frequency