Sound Waves. Vibration of a tuning fork. http://www.ndt-ed.org/EducationResources/HighSchool/Sound/hs_sound_index.htm. Compression (pressure higher). Rarefaction (pressure lower). Pressure Waves. Sound waves is usually analyzed from the point of view
Rarefaction (pressure lower)Pressure Waves
DisplacementPressure and Displacement in Sound Waves
The displacement graph is π/2 out of phase with the
Range of sound frequencies
heard by human ears
SubsonicFrequency Spectrum of Sound Waves
Frequency in Hz on a log scale
1 10 102 103 104 105 106 107 108 /Hz
Note that the audible range varies somewhat from one individual to another.
Where E is the Young modulus and
is the density of the solid rod.
v = 331 + 0.61 TC(m s-1)
generatorMeasuring the Speed of Sound in Air (1)
(1) The sound wave intensity, which depends on
(a) the square of the amplitude,
(b) the frequency,
(c) the speed,
(d) the density of the medium.
(2) The sensitivity of the hearer to the particular frequency
Unit : W m-2
- the energy is distributed through a larger volume,
(For a point source and isotropic medium the intensity
will obey the inverse square law.)
- of attenuation: the wave energy is gradually converted
by an imperfectly elastic medium into the internal
energy of the medium’s molecules.
Intensity level sound in air
DistanceVariation of Intensity with Distance (3)
where r is the distance from the source.
where I = the intensity of sound,
Io= 1 pW m-2(Threshold of hearing)
Unit : decibel (dB)
Source of the Sound
Jet plane at 30 m
Threshold of pain
Loud indoor rock concert
Siren at 30 m
1 × 10-2
Automobile moving at 90 km h-1
3 × 10-5
Busy street traffic
1 × 10-5
Ordinary conversation, at 50 cm
3 × 10-6
1 × 10-8
1 × 10-10
Rustle of leaves
1 × 10-11
Threshold of hearing
1 × 10-12
Each curve represents sounds that seemed to be equally loud.
Note that the ear is most sensitive to sounds of frequency between 2 kHz and 4 kHz.
-making the walls absorbent of
-minimizing the passage of
sound energy through the solid structures of the walls.