The audio spectrum extends from approximaately 20Hz to 20,000 Hz.Sounds of frequency between 20Hz and 20,000Hz can be heard by human ear
Sounds of frequency less than 20Hz are called “infrasonics”.
Sounds of frequency greater than 20,000Hz are called“ultrasonics”.
Ex: Sound produced by bats.
The points of no displacement when standing waves are formed.
The points along the medium which vibrate back and forth with maximum displacement.
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 is the highest or lowest sound an object makes.
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.
The apparent change in the frequency of sound due to relative motion between the sound source and observer is called Doppler Effect.
The sound obtained by reflection at a wall, cliff or a mountain is called an echo.
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.