Characteristics of a sound wave, Frequency, Amplitude, speed, Time period

 

Characteristics of a sound wave

 

There are many characteristics of sound wave.

(1)         Frequency

(2)         Speed

(3)         amplitude

 

 

Distinguish between loudness and intensity of sound

 

(1)         Loudness is a measure of the response of the ear to the sound.

 Intensity is the amount of sound energy passing each second through unit area.

(2)         Loudness is measured in decibels (db). Whereas intensity is measured in watt per meter square (W/m²).

(3)         Loudness is a subjective quantity.

Intensity is an objective quantity.

(4)         Loudness depends on Amplitude.

Intensity depends on the Frequency and the Amplitude of the sound.

(5)         In the Loudness, if the Amplitude is high, the loudness will be high.

The sound intensity is directly proportional to the square of the amplitude of sound wave.

(6)         Loudness is dependent on the sensitivity of the human ears.

The intensity is independent of the sensitivity of the human ears.

 

 

 

 

What are wavelength, frequency, time period and amplitude of a sound wave?

 

Wavelength of a sound wave:--

                                               The distance between two consecutive compression (C) or two consecutive rarefaction (R) is called as wavelength.

The wavelength is represented by the Greek letter l (lambda).

The  SI unit of wavelength is metre (m).

The wavelength, speed of the sound wave and frequency can be related by the equation:--

V   =   n.l

Where as,

V is the speed of the wave

n is the frequency

l  is the wavelength.

Wavelength depends on the medium that is air, water or vacuum that a wave travel through. Sound wave, light wave and electric signals passing through conductor are the examples of the wave.

Here, sound wave is a variation in the air pressure.

The strength of the electric and the magnetic field is varied during the electromagnetic radiation. Same cases happen in the case of light wave.

Water wave is varied in the case of the of the height of a body of the water.

 

 

 

    Frequency of a sound wave:--

                                                Frequency is the number of cycles or vibrations per unit of time. The SI unit of frequency is Hertz. And it is represented by the symbol Hz.

It is also represented by the Greek letter v (Greek letter, nu).

The inverse of the wavelength is called as spatial frequency.

For example:- suppose when we are beating the drum. Then how many times we are beating the drum in unit time is called the frequency of beating the drum.

Here, a sinusoidal wave is moving at a fixed wave speed, then wavelength is inversely proportional to the frequency of the wave. Hence, when the wave has higher frequencies, then there are shorter wavelengths. And when the wave has shorter frequencies, then there are longer wavelengths.

 

Noted:-

           The SI unit of the frequency, Hertz was named after Heinrich Rudolf Hertz.

Heinrich Rudolf Hertz was born on 22 February 1857 in Hamburg, Germany.

He was educated at the university of berlin.

 

 

 

Spectrum:--

                   The range of the wavelength or frequency for wave phenomena is called as a spectrum.

 

Time period of a sound wave:--

                                                 The time taken by two consecutive compressions or rarefactions to cross a fixed point is called the time period of the sound wave.

Or, time taken for one complete oscillation is called the time period of the sound wave.

It is represented by the symbol T.

The SI unit is second (s).

The formula is given below:--

   V = 1/T

amplitude of a sound wave:-- 

                                              the magnitude of the maximum disturbance in the medium on either side of the mean value is called as the amplitude of the sound wave.

It is represented by the letter A.

 the loudness or softness of a sound wave is determined by its amplitude.

The amplitude of the sound wave depends upon the force with which an object is made to vibrate.

 

 

 

 

Tone:-

          A sound of single frequency is called as tone.

Note:-

          The sound which is produced due to the mixture of the several frequencies is called as a note. And note is pleasant to listen to ear. Music is pleasant to listen to ear and it is rich of quality. But noise is not pleasant to listen to ear.

 

 

Guess which sound has a higher pitch: guitar or a car horn?

Pitch is defined as the quality of a sound by determining its frequency scale. It is also called as shrillness. Here, car horn has higher frequency than the guitar. If the frequency is higher it means the sound is more shrill or the sound has higher pitch. If the sound is low frequency, it means the sound is more shrill or the sound has high pitch. The faster the vibration of the source, the higher the frequency and higher is the pitch. Thus high pitch sound corresponds to more number compressions and rarefactions passing a fixed point per unit time. Hence, car horn has higher pitch than the guitar.

 

Noted:- objects of different sizes and conditions vibrate at different frequencies to produce sounds of different pitch.

 

Speed of the sound wave:--

                                              The speed of the sound wave is defined as the distance which a point on a wave such as a compression or a rarefaction travels per unit time.

 

We know,

Speed  =   distance / time

V= l / T

V =  l. n            (1/T  = n  )

V  is the speed of the wave

l is the wavelength of the sound wave. It is the distance travelled by the sound wave.

T is the time period of the wave.

Thus we can say that speed of the wave is the multiple of the wavelength of the sound wave and frequency of the sound wave.

 

Speed = wavelength X frequency

The speed of the sound wave depends upon temperature as well as the medium through which a sound wave is propagating.

In the ideal gas, the speed of the sound wave depends on its temperature and composition.

The speed of the sound wave is varied from substance to substance. Sound wave is faster liquids and fastest in the solids but sound wave is slow in the gases.