Sound_Concept_3
Sound Reception
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Subject facts
Why you need to know these facts.
Vocabulary Amazing facts
Common Misconceptions
Questions
Teaching Ideas
Subject Facts
Although our ears are our main sound receptors, other parts of our bodies are also susceptible to sound vibrations. The sound of a dentist's drill is transmitted very effectively through the teeth. The bass at a rock concert is felt by the stomach as much as it is heard by the ears (in fact, several governments have developed 'riot control' weapons using loud, low-frequency sounds to stun or cause diarrhoea).
The human ear
Our ears provide for most of our listening needs. The human ear has three parts: a collector; a transmitter and a receiver (see Figure.5). The outer ear flap (pinna) collects sound pulses and directs them towards the eardrum, or tympanic membrane. Having ears that are tilted slightly forwards means that we hear things in front of us better than things behind us, The vbrations of the ear drum as sounds hit it are transmitted through the middle ear via three small bones (the hammer; anvil and stirrup) to the oval window at the entrance to the inner ear.
The cochlea, or inner ear is a cone shape rolled up like a snail's shell, with the widest end attached to the oval window. It is filled with fluid, and its inner surface is covered in small clumps of very short sensory hairs, Sounds entering the inner ear make the fluid move and bend the hairs, which transmit signals to the brain. Higher notes cause hairs further inside the cone to bend. The brain interprets these signals as 'sounds'.
Hearing
Sounds can normally be heard in the range 20 to 20,000Hz, though the higher frequencies get harder to hear as you get older. The ear is most sensitive to sounds within the human vocal range.
Some hearing problems can be solved by technological solutions. More sound can be collected by using an ear trumpet to extend the pinna. A hearing aid can be used to increase the volume: the sound is picked up by a tiny microphone, amplified and then retransmitted through a tiny loudspeaker. If the middie ear is failing to transmit, it can be replaced by plastic inserts or bypassed by anchoring a hearing aid to the skull. In some cases, it possible to send sound directly as electrical impulses to the cochlear nerves.
Why you need to know these facts
Ears are our sound receptors, so a basic understanding of how they work is important linking the physical occurrence of sound to how we actually perceive it.
Vocabulary
Pinna — the outer portion of the ear
Eardrum — the membrane which receives sound from the pinna and passes it to the middle ear.
Cochlea - the sound reception part of the inner ear
Amazing facts
Normally humans can hear frequencies up to 20kHz Children with asthma can sometimes hear 30kHz. In tests, people have detected vibrations of 200kHz applied directly to the skull.
Bats make high-frequency (90kHz) squeaks when flying: they use the echoes of these squeaks to detect objects the dark
Questions
Why can't hear very well when I have a cold?
The mucus that blocks your nose can also block your ears! There is a direct connection between the two, which is why you feel pressure in your ears when you hold your nose and try to breathe out. The mucus allows pressure to build up, so the ear drum doesn*t work as well and the sound vibrations are muffled as they travel through the middle ear.
Teaching ideas
Sound direction (exploring, modelling)
This activity is best done in a hall or gym: Blindfold a child and place him or her inside a circle of chi!dren. Point to a child in the circle, who clicks his or her fingers or tongue. Can the blindfolded child point to the source of the noise? Use this to discuss the importance of having two separate ears for locating the source of a sound.
Sound book (using ICT)
The children can use a presentation software package to present a collection of digitally captured sounds and images. They could make an electronic 'book' where the 'reader' dicks on images to hear the sounds that they make ('The cat goes meow'), or clicks on icons to hear demonstrations. For example, xylophone keys and recorded notes could be used to demonstrate the idea of pitch.
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