Reflection of Sound | Physics

Reflection of Sound | Physics


Today I’m gonna start by asking a question Does sound reflects? Yes Sound bounces off a solid or a liquid like a rubber ball bounces off a wall Like light sound also reflect and follows the same laws of reflections as that of light Hence the direction of the sound is incident and reflected makes equal angle with a normal and the three lies in the same plane Here in this lesson let’s discuss about reflection of sound let’s start by discussing a common phenomena called Echo If we shout or clap near a suitable reflecting object such as long building or a tall building or a mountain we will hear the sound back after a while This sound which we hear back after a while is called as an Echo For a normal human being the sound persists in the brain for about 0.1 seconds So to hear a distinct echo the time interval between the original sound and the reflected sound must be at least 0.1 seconds Let’s quickly find out What are the criteria to hear an echo? If the speed of the sound is 344 m/s at a temperature say , 22 degree Celsius We know that the reflected sound should reach the ear of the listener in at least 0.1 second Hence The total distance covered by the sound will be 344 multiplied by 0.1 which gives you 34.4 m Hence To hear a distinct echo from the point of generation will be the half of this distance that is 17.2 m This distance will change with the change in temperature As interesting it may seem to listen to an echo sometimes reflection of sound is not desirable For example a sound created in a big hall persist by repeated reflection of sound this repeated reflection of sound is called as Reverberation so In an auditorium or a big hall this excessive reverberation are highly undesirable To reduce this the roofs and the walls of an auditorium or a big hall is generally covered with sound absorbant materials Now you know why? The movie theater is generally covered with cushion like material Yeah! It is to reduce the reverberation but Don’t think this reflection of sound is always annoying It has lot of practical applications as well It is used in a medical instrument called Stethoscope which is used to hear the sound of human body parts Chiefly, to hear the sound of human heart lungs etc. There the sound of the heart beat reaches the doctor’s ear by using multiple reflection of sound Another major application of reflection of sound is it is used in Megaphones Musical instruments such as trumpets, shenais etc. So, here in this lesson, we have understood Sound also gets reflected like light We also learned about echo Reverberation Advantages and disadvantages of reflection of sound

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