Characteristics of a sound wave
Sound waves have following characteristics:
(1) Amplitude
(2) wavelength
(3) Frequency
(4) Time period (5)Velocity
Amplitude.
The maximum displacement of each particle from its mean position is called amplitude.
It is denoted by A.
Its SI unit is metre (m). Its CGS unit is Centimeter (cm)
Wavelength
The distance between two nearest (adjacent) crests or troughs of a wave is called its wavelength.
It is denoted by the Greek letter lambda (λ).
Its SI unit is metre (m). Its CGS unit is Centimeter (cm)
Frequency
The number of vibrations per second is called frequency.
The SI unit of frequency is hertz (Hz).
The symbol of frequency is ν (nu).
Time period
The time taken to complete one vibration is called time period.
It is denoted by T.
Its SI unit is second (s).
The frequency of a wave is the reciprocal of the time period.
i.e., v = 1/T
Velocity
The distance travelled by a wave in one second is called velocity of the wave or speed of the wave.
Its S.I. unit is metres per second (m/s).
Velocity = Distance travelled/Time taken
⟹ v = λ/T , (where λ = wavelength of the wave travelled in one time time period T)
⟹ v = λv (As 1/T = v)
Thus, Velocity = Wavelength × Frequency
v = λv is called the wave equation.
Pitch and loudness of Sound
Pitch: It represents shrillness of sound.
It depends on the frequency of vibration. Higher the frequency of sound wave, the higher will be the pitch of sound and vice-versa.
Loudness: It is a measure of the sound energy reaching the ear per second.
It depends on the amplitude of the sound wave.
It is measured in decibel ‘dB‘