Definitions [16]
The wavelength of a sound wave is the spatial distance over which the wave's shape repeats. Because sound is a longitudinal wave, it is specifically defined as the distance between two consecutive points in the same phase of vibration.
Define sound ranging.
The process by which bats and dolphins detect the presence of an obstacle by hearing the echo of the sound produced by them is called sound ranging.
Define time period.
The time period of a particle executing S.H.M. is the time taken to complete one cycle and is denoted by T.
The linear distance between the two consecutive particles of a vibrating medium in the same phase is called its wavelength. It is denoted by the Greek letter lambda (λ).
The distance travelled by the wave in one second is called the wave velocity (V).
A pattern which moves through material medium by repeated vibration of the particles of the medium about their mean position without the actual movement of matter is called a wave.
The number of vibrations made by the particle of the medium in one second, is called the frequency (j) of the wave.
Our ears are sensitive only to a limited range of frequencies from 20 Hz to 20,000 Hz, which is called the audible range of frequency.
The sound of frequency above 20,000 Hz is called ultrasonic.
The sound of frequency below 20 Hz is called infrasonic.
When a sound wave travels in a medium, the maximum displacement of the particle of the medium on either side of its mean position, is called the amplitude (a) of the wave.
The time taken by the particle of the medium to complete its one vibration, is called the time period (T) of the wave.
The distance travelled by a wave in one time period of vibration of the particle of the medium, is called the wavelength (λ).
Define the term wavelength.
The linear distance between the two consecutive particles of a vibrating medium in the same phase is called its wavelength. It is denoted by Greek letter lambda (λ).
OR
The distance travelled by the wave in one time period of vibration of the particles of medium is called its wavelength.
OR
In a longitudinal wave, distance between the two consecutive compressions or rare fractions is called wavelength.
Define the following term:
Noise
Noise is defined as any unpleasant, loud, undesired sound that interferes with one’s hearing and concentration, and the pollution caused by noise is termed noise pollution.
Noise is defined as any unpleasant/loud undesired sound interfering with one's hearing and concentration and the pollution caused due to noise is termed as noise pollution.
Key Points
- Noise pollution is an undesirable high level of sound. Included as an air pollutant under Air (Prevention and Control of Pollution) Act, 1981, amended in 1987.
- Sources - machines, transportation, construction sites, industries, festivals and public functions.
- Exposure to 150 dB or more causes permanent hearing loss. Other effects - sleeplessness, increased heartbeat, altered breathing, psychological stress and negative impact on the child's learning.
- Control measures - sound absorbent materials, muffling noise, and horn-free zones near schools and hospitals.
- Supreme Court banned loudspeakers at public gatherings after 10 pm. The government has rules against firecrackers and loudspeakers.
