HEARING

1. HEARING ShirmeenIjaz

2. Sound Wave Properties • Wavelength: The distance between any point on a wave and the equivalent point on the next phase. Literally, the length of the wave.

3. Amplitude: The strength or power of a wave signal. The "height" of a wave when viewed as a graph. • Higher amplitudes are interpreted as a higher volume, hence the name "amplifier" for a device which increases amplitude.

4. Frequency: The number of times the wavelength occurs in one second. Measured in kilohertz (Khz), or cycles per second. The faster the sound source vibrates, the higher the frequency. • Higher frequencies are interpreted as a higher pitch. For example, when you sing in a high-pitched voice you are forcing your vocal chords to vibrate quickly.

5. Pleasant and unpleasant sounds • Some sounds are pleasant and some are a noise. Compare the two waves on the right. A pleasant sound has a regular wave pattern. The pattern is repeated over and over. But the waves of noise are irregular. They do not have a repeated pattern.

6. Humans can hear sounds that range from about 20 to 20,000 hertz. • Children have more sensitive ears than adults. They can recognize a wider variety of noises. • Dolphins have the best sense of hearing among animals. They are able to hear 14 times better than humans. • Animals hear more sounds than humans. • An earache is caused by too much fluid putting pressure on your eardrum. Earaches are often the result of an infection, allergies or a virus.

7. If a person is looking straight a head and a sound comes from his left, it reaches his left ear before it gets to the right one. • The delay between when it reaches the first ear and when it reaches the second is about 600 to 700 milliseconds, or 0.6 to 0.7 seconds. • Human use this sort of information to determine a sound’s location.

9. Outer ear Outer ear consist of • Pinna • External auditory canal. • Pinna: The outer funnel like part of the ear. Function: It helps to collect sound vibration near the opening of the ear, direct sounds waves into the external auditory canal.

10. 2) External auditory canal: It’s a 1 inch long passage way connected to the tympanic membrane. Function: this canal conduct sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane.

11. Middle ear • Tympanic membrane (ear drum) • Auditory ossicles ( malleus, incus, stapes) 1) Tympanic membrane (ear drum): • It is a thin, tough, flexible, fibrous membrane. • Attached to the external auditory canal. • It is a cone shaped and grey in color. • A membrane that vibrates when sound waves reach it. • The tympanic membrane protects the middle ear and conducts sound vibrations from the external canal to the ossicles.

12. 2) Auditory Ossicles: The middle ear contains 3 smallest bones ( the ossicles) of the body. • Malleus (hammer) • Incus (anvil) • Stapes (stirrup) 1) Malleus (hammer): From one side it is connected to the tympanic membrane and to the second it is connected to the incus.

13. 2) Incus: The middle of the 3 ossicles connecting the malleus and the stapes. 3) Stapes: Connected to the incus on one end, and to the cochlea on the other end. Functions: Their function is to amplify sound vibrations. Malleusvibrates Incusvibrates Stapes

14. Inner ear Inner ear consists of: • Oval window • Round window • Cochlea • Oval window: Membrane that connects the middle ear with the upper half of the cochlea. 2) Round window: Membrane that connects the middle ear with the lower half of the cochlea.

15. 3) cochlea: The cochlea  cochlea is a snail-shell like structure. It convert vibrations of sound into nerve impulses leading to the brain. The cochlea is filled with a watery liquid, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, thousands of "hair cells" (hear receptors) are set in motion, and convert that motion to electrical impulses, which travel along the auditory nerve to the brain.

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