SOUND

Longitudinal Waves

All sound is produced by

material sends through a thru

Frequency of = frequency of

Pitch =

High pitch = high

Low = low vibration frequency

Range

Below 20 Hz =

Above 20,000 Hz =

Young person can hear

Compression

Pulse of

Rarefaction

Closing door

Molecules away from

All

Sound is in than in

Sound is

Sound cannot

No compression/expansion,

There can be without produced

SPEED OF SOUNDDo you hear thunder or see lightning first?

Speed of sound in dry air @ is

increases speed

increases speed

Each increase, speed of sound increases by

Speed of sound @ (~20°C) =

Speed of sound in a depends on , but on !!!

INTENSITYproportional to the of a

objective

LOUDNESSa sensation

BUT, related to

almost varies as the

unit =

increase of each = sound intensity increases by a

10 dB = 10 x as

20 dB = 10 x as ; 100 x as

Source of sound Level (dB)Jet engine @ 30m 140Threshold of pain 120Loud rock music 115Old subway train 100Average factory 90

Busy street traffic 70Normal speech 60

Library 40Close whisper 20

Normal breathing 10Hearing threshold 0

TABLE 26.1; P394