The audio spectrum extends from approximately 20Hz to 20,000
Hz.Sounds of frequency between 20Hz and 20,000Hz can be heard by
human ear
Infrasonic sounds:
Sounds of frequency less than 20Hz are called �infrasonics�.
Ultrasonic sounds:
Sounds of frequency greater than 20,000Hz are
called�ultrasonics�.
Ex: Sound produced by bats.
Nodes:
The points of no displacement when standing waves are
formed.
Antinodes:
The points along the medium which vibrate back and forth
with maximum displacement.
Sound Intensity:
The loudness of sound is directly proportional to the square
of the amplitude or intensity (I). It is convenient to use a
logarithmic scale to determine the intensity level b = 10 log
(I/I0)
Pitch:
Pitch is the highest or lowest sound an object makes.
Beats:
Beats are the periodic and repeating fluctuations heard in
the intensity of a sound. Two sound waves of nearly same
frequencies interfere with one another to produce beats
The intensity of the resultant wave at a given point in the
medium becomes maximum (waxes) and minimum (wanes) periodically.
Doppler Effect:
The apparent change in the frequency of sound due to
relative motion between the sound source and observer is called
Doppler Effect.
Echoes:
The sound obtained by reflection at a wall, cliff or a
mountain is called an echo.
Diffraction:
When waves encounter an obstacle with an edge, some of the
wave energy bends around the edge behind the obstacle. This
bending is called diffraction.
