Sound

Sound
Sound
               Sound is form of energy.
Production of Sound
               Sound is produced by all types of vibrating objects.
Nature of sound propagating
                         Sound is a example of mechanical wave. Which need medium for their propagation. The sound energy vibrates the participles of the medium parallel to the way of propagation.

The sound waves propagate through medium due to difference of pressure at different regions of the medium. The portion of the medium where the pressure is high called compression. And the region where pressure is low called rarefaction.
So the sound waves propagate in the form of compression and rarefaction. Sound wave is also called longitudinal waves.
Characteristics of sound
         Basically the sound possessed the following main characteristics.
    loudness of sound
    Intensity of sound
    Pitch of sound
    Quality of sound
Loudness of sound
             The differentiation between the faint and loud sound is called loudness of sound.
Loudness of sound depends upon the five main factors.
  1)       The amplitude of vibrating objects.
  2)       The direction of medium.
  3)       The distance between the observer and transmitter
  4)       The area of vibrating objects.
  5)       The temperature of the medium and condition of observer.
Intensity of sound
Definition
         The number of sound wave passes through cross sectional area (A). The cross sectional area held perpendicular to the way of propagation of the sound waves. The Intensity of sound is independent of the loudness of sound. Intensity of sound is denoted by (I).
Derivation
                The sound energy (E) passing through any cross sectional area (A) in given time (t). The cross sectional area (A) must be perpendicular to the way of propagation.
 Intensity of sound=Sound Energy/Area*time
 I=E/A*t
 Energy=Work
  E=W
 I=W/A*t
 I=W/t*1/A
As power=Work/time
 I=P*1/A
 I=P/A
Weber Fechnar Rule or Law
                          Weber Fisher law makes relation between the intensity (I) of the sound and its loudness (L). This stated As That
 The loudness (L) of the sound is directly proportional to the (Log ) of the Intensity (I).
 Mimetically
 Loudness Log (Intensity)
 L Log I
 L=constant Log I
 L=K log I
       Where If intensities varies by amount of 10, 100, 1000, 10000 ... Then loudness varies by amount of 1, 2, 3, 4. .... And (K) is the constant of proportionality which shows that the ratio between (L) and (I) are always constant.
Threshold of hearing
Threshold of hearing=Faintest audible sound
 I=10 -12Wm 2= 0 Decibel (db)
So we use Decibel denoted by (db) is the unit used to measure intensity of sound.
Intensity level or sound level
                The difference between the loudness of two sounds is known as the Intensity of sound level. It is denoted by Delta L
Pitch
          The differentiation between the grave (loud) and shrill sound is know as Pitch of the sound. Pitch of the sound depends upon the frequency.
  High frequency sounds have high Pitch.
  Low frequency sounds have low Pitch.
Example
            Women have higher Pitch. Where as men have low Pitch. The high Pitch sound moves fast ad travel high distance as compare to low Pitch.
Quality of sound
                            The differentiation between two same identical waves (same wave length, same amplitude, and same frequency) but the sounds are produced by two different instrument. This is due to the difference of the shape of the sound waves which is produced by two instruments.
Music and Noise
  Music
           The sounds which produce pleasant effect on the sense of hearing is known as music. OR The sound which changes gradually its frequency, wave length and amplitude is called music.
 Noise
            The sound which produced unpleasant effect on the sense of hearing is known as noise. OR The sound in changes suddenly is called noise.
Speed of sound
                      It is a devise which is used to find out the approximate value of speed of sound.
Resonance force
                     When two identical waves interact with each other and there frequencies match with each other, they reinforce each other and the resultant frequency is the sum of two waves which is known as resonance force.
Audible frequency Range
                         We know that sound is produced by a vibrating body. A simple pendulum also vibrates but it does not produce any sound. The reason is that its vibrations are very slow. A human ear can hear a sound only if its frequency lies between 20Hz and till 20,000Hz. Sounds of frequency beyond 20,000Hz are inaudible because the eardrum can not vibrate so rapidly. The audible frequency range differs a little for different persons. And it also decreases with age, Young children can hear sounds of 20,000Hz frequency, but old people can not hear sounds even above 15,000Hz frequency.
Ultrasonics
                  We know that human ear can not hear sounds of frequency less than 20Hz or more than 20,000Hz. Sounds of frequency higher than 20,000Hz, which are inaudible to human ear, can be produced and utilized many useful ways. Such sounds are called ultrasonics.