Sound Physics Spring 2002

Sound waves n Longitudinal or compressional waves n Sound waves move through a medium n Sound waves move faster through a solid than a liquid and slowest through gases n Pitch is related to frequency n Loudness is amplitude

Pitch n The frequency of sound is called a note. n Two notes with frequencies of 2:1 are one octave apart. –220 Hz is one octave away from 440 Hz and two octaves away from 880 Hz n “C” has a frequency of 262 Hz

Loudness n Loudness is measured in decibels –Decibels are a ratio of the intensity of a sound to the intensity of the most faintly heard sound. –A sound with ten times the intensity will only sound twice as loud. n The loudest intensity we can bear without pain is times greater than the faintest whisper we can hear. –Approximately 160 dB

The Ear n Outer ear: Fleshy visible part that collects sound, ear canal, and ear drum n Middle ear: Three tiny bones in an air filled space which transmit sound from the ear drum to the inner ear n Inner ear: Transmits sound through a watery liquid to the tiny hair cells in the cochlea.

Doppler effect n Frequency seems higher if sound is coming toward you. n Frequency seems lower if sound is moving away from you. n Frequency from the source does not change.