sound and hearing

Sound and Its Properties

• Sound produced by vibration.

• Sound travel in straight path.

• Sound travel in medium.

• Sound cannot travel through vacuum.

• Sound can be reflected and absorbed.

Properties of Sound-Vibration

• Sound produce by vibration.

• When an object vibrates, its kinetic energy is changed into sound energy.

• Kinetic energy- sound energy

Properties of Sound- travel in medium

• Transfer in form of sound waves.

• Sound travel through medium solid, liquid, and gas.

• Speed of transfer in different medium-increasing speed from gas –liquid-solid

• Particle in the solid are very compact, thus the sound vibration can pass very quickly from particle to particle

Properties of Sound -Sound cannot travel through vacuum.

• Because there is no atmosphere in moon, outer space. Sound need medium to travel. But outer space is just vacuum space without medium for sound to travel.

• Sound cannot travel through vacuum.

Properties of sound- sound reflection

• Sound can be reflected by surface-produce echo

• Hard surface reflects sound better than soft surface

• Ex: Walls of buildings, tunnels, glass, metal

Properties of sound-sound absorption

• Reflected sound is always weaker than the original sound because part of the sound energy has been absorbed by the reflecting surface.

• Sound can be absorbed by a surface.

• Soft surface is better absorber of sound.

• Ex: carpets, curtains, cotton, sponge, rubber, soft board.

• The soft cushions and padding in car absorb sound from engine.

Application of sound reflection

• Determine the depth of sea

• Detect the fish in sea

• Detect the petroleum in ground

• Guide the flight of bats and movement of dolphin (night).

Defects of Hearing

• Hearing defects means ear is not working correctly or as well as it should.

• It may occur in more than one part of the ear.

• 1. DEAF-full or partial decrease in the ability to detect or understand sounds.

Deaf usually caused by :

- Eardrum is torn-cannot function

- Ossicle bone fused together-can’t vibrate

- Auditory nerve damaged by loud sound

- Cochlea damage due to sickness/ drugs

• 2. Temporary hearing loss-build-up of earwax

• 3. Presbycusis- hearing loss related to aging and other factors.

Correcting hearing defects

• Syringes and warm water –remove wax

• Replace damaged ossicles

• Surgery- damaged eardrums

• Electronic gadgets - implantation

Limitation of Hearing

• Definition: The range of sound that human can hear. 20-20000Hertz

• Limitations of hearing varies with people

Range of hearing in different individual

• Children have eardrums that are more elastic. As a result, they can hear better.

• As people age, their hearing deteriorates. Their eardrum become less elastic. The range of sound frequencies that they can detect decrease. Their ability to hear high-pitched sounds decrease.

• Person exposed to constant loud noise experiences a loss of hearing-range of hearing is smaller than normal people.

Devices to enhance hearing

1. Earphone-Connect the sound from electronic gadgets to ears-change electrical signals into sounds that ear can detect

2. Stethoscope-amplify the sound of heartbeat

3. 3. Microscope-Change soft voice into electrical signals –change into loud voice

Stereophonic Hearing

• Definition: The hearing that involves the use of two ears

• The sound coming from right will be detected by our right ear slightly earlier than our left ear-produce stronger vibration

• The ear nearer to the sources of sound receives:

- The sound earlier than other ear

- Stronger stimulus-impulse-brain-interpret

• The louder and the earlier sound detected by our right ear when compared with the softer and delayed sound detected by left ear tells us that the sound comes from the right.

• Functions: Enables us to determine the direction of sound accurately

- avoid danger

- Survival of animals