Acoustic phenomena

INTRODUCTION
Acoustics is a branch of physics which deals about the production, control, transmission, reception
and effect of sound wave. The term is derived from Greek word “akoustos” which gives the meaning
. This branch studies all properties of mechanical waves in solids, liquids and gases. The
many aspects of human society music, medicine, architecture,
industrial production, welfare and many more. In this chapter, we primarily focus on the intensity,
quality, beats and Doppler’s effect of sound wave.

CHARACTERISTICS OF SOUND
We hear many kind of Sound in Our daily life. The horn of vehicles, the Sound of engines, music in
radio and television, warbling of birds, etc. are Some examples of sound with which we are familiar
in our day to day life. If we start listening to our favorite music, then we don’t want to turn the
radio off. But, if we stay at the traffic chowks of crowded city, we do not like to stay there any more
because of irritating sound. There are various types of Sound we hear, but in physics, the sound is
broadly categorized into two types (i) musical Sound and (ii) Noise.

i) Musical Sound: The Sound which is regular, periodic and continuous is called musical sound.
Music is pleasant to hear. Someone may say that s/he does not like the melody of a song, so it is
noise for her/him. But, in physics, the musical sound does not solely depend on personal sense,
rather, it is a pattern of sound generation and propagation. If a sound contains regular and
periodic vibration, this sound is certainly a music, though someone like or dislikes it. In musical sound, the frequency is generally high.
ii. Noise: The sound wave which is irregular, non-periodic, and very short in duration is called
noise. Noise is unpleasant to us. Sound of engine, horn of vehicles, hammer striking on anvil
are some examples of noise.
Characteristics of Musical Sound
The musical sound is basically distinguished
energy flow and pattern of propagation.
divided into three types: pitch, intensity and quality.
Pitch
The characteristics of musical sound which is pertaining to frequency is known as pitch. Pitch is
somehow perception, though it depends on frequency. Pitch of sound is a subjective quantity. high
frequency sound is called the high pitch sound. I ugh pitch sound is shriller than the low pitch sound
Although the frequency of sound produced by a source is constant, its Observed frequency may be
different due to the relative motion between the sound source and the observer.
If we compare the sound of mosquito with the roaring of lion, We certainly find
propagation in the roaring of lion is greater than the sound of mosquito. But, if we compare the pitch
of these sounds, the pitch of sound of mosquito is greater than the roaring of lion (i.e. the sound of
mosquito has greater frequency than the frequency of sound produced in roaring of a lion). Other
many examples that we experience in our daily life are:
1. Voice of female has greater pitch than the voice of male.
2. Voice of child has greater pitch than the voice of adult.
3. The sound produced by thin wire has greater pitch than the thick One.
The sound produced by different keys of harmonium has different pitch.
5. The flute produces sound of different pitch when different holes are Closed.

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