Characteristics of Sound WaveThere are five characteristics of sound. They are:
Speed or Velocity, Amplitude, Frequency, period, Wavelength
Figure 2: Characteristics of Sound Wave
Amplitude is the displacement of the particle of the medium from its original position when the wave is passed through it. If the displacement of the particle is maximum, it is understood that the Amplitude is high. As a result, the sound is also high.
Similarly, if the displacement of the particle is less, then the vibration is also less. It is understood that the Amplitude is less. As a result, the sound is low. Amplitude is denoted as A
Its SI unit is the meter (m).
The number of vibrations produced (waves or cycles) produced per second is called the frequency of the wave. The SI unit of Frequency is S-1 or Hertz(Hz). A human ear can recognize sound only that ranges from 20 Hz to 20,000 Hz.
The sound which is less 20Hz is called Infrasonic Sound. A sound that is greater than 20,000 Hz is called Ultrasonic Sound. A human ear cannot recognize or hear a sound that is below 20 Hz or about 20,000 Hz.
Simply Humans cannot hear Infrasonic and Ultrasonic Sounds.
The time needed for one complete cycle or wave or vibration is called Time-Period of the wave. The time period is denoted as T. The SI unit of the time period is Second (S).
The frequency and time are reciprocal to each other. That is T=1/F or F=1/T.
The shortest distance in which a wave repeats itself is called Wavelength. The distance between the centres of two back-to-back compressions or rarefactions is called Wavelength.
The wavelength is denoted by λ. The SI unit of wavelength is the metre (m).
Velocity is simply the distance traveled by a sound wave in one second. The unit of Velocity is MS-1 ( M/S).
In big halls the sound produced from the speaker hits the wall, the multiple echoes are produced and are reduced to a value to zero after some time. This persistence of sound due to multiple reflections is called reverberation.
In cinema halls or theatres is designed such a way that the reverberation is optimal for a good audio experience. The walls, floor, etc are fixed with sound absorbers such as rough plaster, draperies, flannel cloths, fiberboard, etc.
Also, seats are made of sound-absorbing materials. A cinema hall is the one that provides good audio and video experience. A poor audio experience disturbs the cinema experience.
There is a separate branch in physics called Acoustics, where it deals with designing of Cinema Halls, theatres, auditoria etc.