Reproduction of Sound (Disc Reproduction)

Disc Reproduction 

The disc reproduction of sound can be done by various two methods which are as follows :

1. Mechanical Method

2. Electrical Method 

We will discuss both of these methods below in details .

1. Mechanical Method :- 

The mechanical method for the reproduction of sound is generally used in Gramophones .

In this method the sound is reproduced from record with the help of a sound box . 

Construction of Sound Box :- The sound box used for the reproduction of sound is consist of a metal or mica diaphragm which closes the aperture of a cylendrical box . Diaphragm is supported at its edge between two solid rubber rings while the centre of diaphragm is attached to the upper end of a lever . The lever made up of metal is controlled by the two springs A and B . At the lower part of the lever , a fine needle is clamped . The lower arm of the lever is constructed .much shorter than the upper arm due to which the vibrations of the needle are magnified to a larger extent . The whole arrangement of sound box is shown in the figure below .

Working of Sound Box :- The sound box start working when the record starts rotating with the needle in the groove . The waveform cut in the groove forces and the needle moves to and fro sideways and give the response to the recorded sound waves . These vibrations from needle are now communicated to the diaphragm through the lever due to which the diaphragm starts vibrating and reproduces the original sound waves of Record in air .

• The diaphragm should function like a piston to reproduce the noiceless and pure sound .

• The needle used in this process should be very thin .

2. Electrical Method :-

The sound box used in the previous method is replaced by 'Pick Up' in this electrical method . The pick up is used in conjunction with an amplifier and a loudspeaker . The pick up works on the principle of Electromagnetic Induction. 

Construction of Pick Up:- In the structure of a pick up , a permanent horse shoe magnet is used with a fixed coil CC . There are four pole pieces of this horse shoe magnet  named below as N1 , N2 , S1 and S2 . A needle with an iron armature is properly clamped by rubber pads .

The lines of forces get linked with armature from N2 to S1 and N1 to S2  respectively as the position of the needle changes (shown in the figures below) .

Here A is amplifier .

Working of Pick Up :- As the needle moves along the sound track , it begins to vibrate and a varying flux passes through the coil due to which , a varying e.m.f. is generated in it . In other words , the vibrations of the needle generates varying e.m.f. in the coil of Pick Up in accordance with the sound waves in the groove . These sound waves or induced e.m.f. in the coil of pick up is amplified by an amplifier and then finally , it sends to the air through a loudspeaker . 

• There is a very vital role of amplifier in the electrical method of reproduction of sound because the grooves in a record have small amplitudes and therefore the low notes cannot be recorded in their full intensity because they require a greater amplitude .

This was all about the standard methods of reproduction of sound . The recording and reproduction of sound is done on tale recorder (Magnetic sound recording) and on cinema films too . Ask me in the comment section if you want an article on both of these .

I hope that it was helpful to you and you liked it . Keep reading and stay tuned .