Capturing and Reproducing Sounds
If sound is caused by vibrating objects, and every object vibrates in its own unique way, then how are headphones or loudspeakers able to play back such a diversity of sounds?
How Can Headphones and Loudspeakers Create So Many Different Types of Sound?
The secret is in the recording process, and the way in which MicrophoneA tool for capturing sound wave vibrations as they travel through the air.Microphones and LoudspeakerA loudspeaker is an instrument designed to reproduce sounds. It takes an electrical signal and coverts it in to sound wave vibrations in the air.Loudspeakers work.
Microphones come in many shapes and sizes, but in each case their job is to translate the vibrations in the air into information that can be stored.
With computers this information about sound wave vibration is stored digitally.
Sound In -> Microphones
Microphones work by sensing sound wave vibrations in the air and converting these into electrical information.
Inside them they have a sensitive diaphragm that moves in response to the sound (much like the ear drum).
This movement is converted into electrical signals which can then be stored or sent to loudspeakers.
The pattern of movement will be different for each different sound wave. Microphones are sensitive to a wide range of different sound wave patterns and so can record many sounds.
Nearly all recording today uses the properties of electricity. Electrical currents can become stronger and weaker and this property can be used to record the fluctuating pattern of sound wave vibrations.
Electrical energy (power) is usually stored in the form of direct current because an alternating current would mean that devices would repeatedly turn off and on.
Audio signals tend to be alternating currents because they have to store information about sounds, which are back and forth (alternating) vibrations.
Sound Out -> Loudspeakers
To reproduce sounds we need to be able to reproduce the soundwave vibrations made by the original object. When we imitate sounds with our voice this is exactly what we do (for example: if we imitate the sound of a passing car, or an animal).
But to recreate sounds accurately we need to be able to reproduce the soundwave vibrations in detail. Loudspeakers receive electrical signals and convert them into soundwave vibrations.
The higher the quality of the loudspeaker, the more detail of the sound wave can be recreated and therefore the better the quality of sound reproduction.
The loudspeaker takes electrical information (the alternating current that is produced through the process of capturing sounds) and converts it into sound wave vibrations.
It produces sound wave vibrations by moving a cone back and forth (in much the same way that an object vibrates to produce sounds, see ‘Where Do Sounds Come From?‘).
The process of converting electrical signals into physical sound wave vibrations is made possible by the connection between electricity and magnetism.
Inside a loudspeaker is an electromagnet (a magnet that turns on and off), which is attached to the base of the speaker cone. Any (alternating) electrical signal which reaches the loudspeaker causes this electromagnet to turn on and off, and as it does so the speaker cone is pulled back and forwards. The process of this speaker cone moving back and forth produces sound wave vibrations in the air.
Sometimes loudspeakers have more than one cone. This is because bigger cones are better at creating bigger (lower frequency) sound wave vibrations and smaller cones are better at producing smaller (higher frequency) sound wave vibrations.
Headphones are actually a special type of loudspeaker.
Instead of being on the desk or a stand in front of you, the two headphone loudspeakers are positioned directly next to your ears (one loudspeaker for each ear).