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Dye
A substance that has an intense colour and is used to tint materials (See: Colourant).
When a material is dyed, dye molecules come out of the dyeing solution and attach themselves onto the material to be dyed in such a way that they cannot be removed. The chemical used to help fix
the dye is called a mordant. The mordant is put onto the material before the dye. When the dye is applied, the coloured chemicals in the dye combine with the mordant to fix the colour permanently.
Ear
Most modern, commercial dyes are made from crude oil.
Dynamic range
The frequency range over which the ear can hear, or a loudspeaker can produce sound. The dynamic range of the ear is greater than
any speaker system can match. (See also: Sound level.)
E
Ear
The body’s sound receiver. One of the most sensitive organs of the body, it is able to hear sounds
that range over 10 octaves (15Hz to 20,000Hz) (see: Hearing) and sound intensities over a range of 1,000 billion to one. When the
ear detects the faintest possible sound, it moves just a billionth of a centimetre. The ear can also detect a frequency difference of only a few cycles per second.
Two ears allow us to detect the direction the sound is coming from. The brain is able to sort out the many different sounds we hear in, say, a noisy street and focus on just one of them.
The ear and brain are able to pick out each new sound wave that reaches it and ignore the echoes. That makes it possible to understand speech in a room with reverberation (most rooms).
Inner ear
The ear is made of three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of the part of the ear you can see, as far as the ear-drum. The middle ear reaches from the space behind the ear-drum to another, thin kind of ear-drum, called the aperture. The inner ear is a curled tube containing many fine hairs that detect the sound waves and change them into electrical signals. There are about 30,000 sound-detecting hairs and they all combine into one ‘cable’ that is less than a millimetre across. This cable goes directly to the brain.
When sound reaches the ear, it is channelled down to the ear-drum, which makes the ear-drum vibrate. On the other side of the ear-drum are three small bones that transfer the vibration to the aperture at the end of the inner ear. The inner ear is filled with a fluid. As the aperture vibrates, it sets the fluid in motion, and this sets the hairs of the
inner ear into motion. Movements of the hairs then create the electrical signals that go to the brain. The hairs are of different lengths, so they vibrate at different frequencies. That is how we can tell one pitch from another.
 Ear – The parts of the ear.
Coiled tube with sensor hairs of the inner ear
Bones of the middle ear
Ear-drum
Middle ear
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