LIMITATION 

1. We cannot hear all the sounds around us.
2. The range of frequencies of hearing in man is 20 Hz until 20 000 Hz.
3. Different people have different limitations of hearing.
4. For example, old people generally cannot hear as well as young people.
5. Our ear drum become less sensitive to sound as we grow older.
6. To overcome the limitations of hearing, we use
 i. the stethoscope – enables doctor to detect the soft heartbeats of patients.
 ii. hearing aids – collects sound signals before being sent to the middle ear.
 iii. amplifier – boosts weak sound signals.

STEREOPHONIC HEARING

1. Stereophonic hearing is hearing using both ears.
2. The advantages of stereophonic hearing:
i. enables the direction of the source of hearing to be detected more accurately.
ii. This is because the ear nearer the source of sound receives sound louder and earlier than the other ear.
iii. Animals that have stereophonic sound can detect the presence of preys and predators more quickly.

Properties of sound 

1. The transfer of sound requires a medium.
2. sound can transferred through;
   b. solids
   c. liquids
   d. gases
   e. cannot be transferred through in vacuum.
3. Sound can be transferred fastest in solids and slowest in gases.
4. This is because the particles in solids and liquids are closer each other compared to the molecules in gases.
5. Vacuum is space that does not have any particles.

REFLECTION AND ABSORPTION OF SOUND

1. Sound can be reflected or absorbed by the surface of an object.
2. The sound reflected repeatedly from one surface is known as echo.
3. Surfaces that are smooth, even and hard are good sound reflectors and produce loud echo.
 For examples, concrete, plank, metal and mirror
4. Surfaces that are rough, hollow and soft are good sound absorbers and produce weak echo.
For examples cloth, sponge, cork, rubber, carpet and cushion

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努尔哈尼族

Short Biodata

问候。我住在莎阿南和东姑 tunku kurshiah college. 这个博客是一所学校的项目为我的课。