Amplification of sounds

Sounds can be made louder or amplified in a number of ways. By providing more energy in making the sound its loudness can be increased. This would be achieved by beating a drum with greater vigour, blowing harder on the recorder or using more bodily energy in shouting louder.

Electricity can supply the extra energy need to increase the volume of sound, for instance in a Hi fi amplifier. When a stylus rests in the grooves of a rotating vinyl record, it is made to vibrate with very small movements. These movements are turned into small electrical impulses and sent to the amplifier of the Hi fi system. Here the small electrical currents are made larger and sent to the loudspeaker system where they are converted into the much larger vibrations of the speaker cone. A microphone picks up the small vibrations from the voice in a similar way. The tiny movements inside the microphone of a coil of wire inside a strong magnet can be turned into small electrical impulses. These, once more can be amplified by an electronic system and made to drive a loudspeaker.

The volume of sound we hear can also be increased by funnelling it into the ear. The outer ear already provides a funnelling effect but a hearing trumpet will improve this. Holding our hands behind our ears will also have an impressive effect on the volume of sound received.

A fourth way in which sounds can be amplified is seen on the acoustic guitar, violin, drum, xylophone and many other instruments. This is a hollow sound box made of rigid material and often with a hole in. The small sound made by the instrument enables the sound box to reverberate and thus to project the sound further away from the instrument.

Contents

What is sound, Vibration
Sounds travel
The speed of sound in air, Sound travels in solids and liquids too, Hearing sounds through solids
Receiving vibrations at the ear drum, Amplitude of vibrations and loudness
Frequency of vibrations and pitch
Self Assessment