Detecting sounds...

(a) Ears detect sounds,but do not process them.The ear converts the energy of sound waves into the energy of patterns of tiny electrical signals called nerve impluses.These go along nerves to the brain and reach the part called the auditory centres.Here the patterns are sorted and processed,compared with information in the brain's memory,and passed to the conscious,thinking centres of the brain,resulting in whether are you aware to the sounds and identify them.

(b)Similarly,a microphone works ina way same to an ear.It also converts patterns of sound waves into corresponding patterns of electrical signals.These go along a wire to an amplifier,which makes the signals stronger.The electrical signals can be altered by various means,such as booasting low frequency and then fed into a loudspeaker or earphones so that they are turned back into sounds waves.

Recording sounds...

In 1877,the recorded and played-back sound started with the words 'Mary had a little lamb'.American inventor,Thomas Edison and his machine-maker John kreusi designed and made a new machine,named the phonograph.They had this idea while working on another device,a repeater to send (or repeat) electrical telegraph message.The phonograph was the first working device to record sound in a phsical form and play them back again.

The original phonograph stored or recorded the sound in the form of a groove.This was pressed by a metal point,called a stylus,in a layer of tin foil covering a brass cylinder.It was a mechnical system of moving parts and so it did not use any electricity.

Other inventors soon improved the quality of the recordings by replacing the foil with hard wax,in which the metal stylus cut a groove.In 1888,Emile Berlinda introduced a flat disc instead of a cylinder.He also devised a method whereby the stylus moved from side to side,rather than up and down like Edison's original system.By 1904,Berlinda had made an improved version that could be mass produced to a high-quality standard.The concept 'record' was borned.During the early 1900s,the first commercial recordings were made of singers,musicians and speakers.