AP 8th Class Physical Science Notes Chapter 5 Sound
→ Amplitude : The maximum displacement of vibrating body from its mean position is called amplitude.
→ Eardrum : The thin membrane at the end of auditory canal.
→ Frequency : The number of vibrations per second is called frequency.
→ Hertz (Hz) : The frequency is expressed in hertz (Hz)
→ Larynx : In humans, the sound is produced by the larynx.
→ Loudness : Larger the amplitude of vibrations, louder is the sound.
→ Noise : Unpleasant sounds are called noise.
→ Oscillation : The to and fro motion of an object is called oscillation motion.
→ Pitch : The shrillness of a sound is known as pitch (or) Sound of higher frequency produce shrillness.
→ Time Period : The time taken by a pendulum to complete one oscillation is called the time period.
→ Vibration : The to and fro or back and forth motion of an object is termed as vibration.
→ Voice Box : Upper end of the wind pipe, below the hard part on the throat is called the voice box.
→ Wind Pipe : It is passage for the inlet and outlet of air in the lungs.
→ Audible Frequencies : For human ears the range of-audible frequencies is roughly from 20 to 20,000Hz
→ Medium : The substance which allows the passage of sound called medium.
→ Vacuum : Condition of no medium or without medium.
→ Sound is produced by vibrating body.
→ Human beings are able to produce sound with the help of vocal cords.
→ Sound travels through a medium (gas, liquid or solid).
→ Sound cannot travel through vacuum.
→ The eardrum senses the vibrations of sound. It sends the signals to the brain. This process is called hearing.
→ The number of oscillations or vibration per second is called the frequency of oscillation.
→ The frequency is expressed in hertz ( Hz ).
→ Larger the amplitude of vibration, the louder is the sound.
→ The intensity of sound is measured in decibels (dB).
→ Higher the frequency of vibration, the higher is the pitch, and shriller is the sound.
→ Sound pleasant to listen are called music and unpleasant to listen are called noise.
→ Excessive or unwanted sounds lead to noise pollution. It may cause to health problems for human beings.
→ Attempts should be made to minimise noise pollution.
→ Plantation the roadside and elsewhere can reduce noise pollution.