Characteristics of Sound – Physic Notes

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Characteristics of Sound
Characteristics of Sound

What is Sound?

➧ Sound is a form of  energy  which is created by a vibrating object.
➧ In other words Sound is a form of energy. Each particle transmits its energy to its adjacent particles.
➧ Most important Characteristics of Sound is that, Sound is a Longitudinal wave and it cannot travel through Vacuum. For the propagation of sound it must need an elastic medium.

For detailed info about the Sound waves – See the topic Types of Waves

What are the characteristics of sound waves?

There are 4 major Characteristics of Sound these includes_
☛ Loudness
☛ Intensity
☛ Pitch
☛ Quality
♦ With the help of this characteristic we can distinguish two distinct sounds differently.
Let’s discuss all the major Characteristics of a Sound Wave one by one _


Loudness is an auditory sensation, in which our ear can precepts a sound.
➧ It is a subjective Quantity.

➧ The  loudness or softness of a sound  depends on the  Amplitude of that sound wave.

➧ The  Loudness is directly proportional to the square of the Amplitude of the sound wave.

➧ The Loudness of a sound wave is Inversely proportional to the square of the distance between the source.

➧ Loudness also depends on the density of the medium, More density means more loudness.

➧ Also, it depends on the Surface area of the vibrating body , more surface area produced more loudness.

➧ What is Amplitude?
◘ The magnitude of a wave is defined by the of the maximum disturbance of a wave  in the medium on either side of the mean position .

◘ It is usually represented by the letter A

◘  Compared to the  soft sound a Louder sound can travel a larger  distance, because louder sound has   higher energy.

Characteristics of Sound - Amplitude
Amplitude a distinct feature of sound

♦ Unit of Loudness
◘ Phon
◘ Sone
◘ Decibel (dB)

♦ The unit Phon is used to indicate an individual’s perception of loudness.

♦ By definition, 1 phon is equivalent to 1 decibels at 1000 Hz (1 kHz).
1 Sone sound is defined as a sound whose loudness is equal to 40 phons

◘ Loudness of Sound greater than 120 dB, considered as Noise.
♦ Loudness is subjective quantity, as because it varies person to person.

Loudness is a subjective quantity, as it depends  on the sensation of hearing of a person.  To  solve this problem instead of calculating loudness of the sound we calculate Intensity of the sound.



➧ The amount of sound energy passed per unit time through a unit area called the Intensity of sound. The area is perpendicular to the direction in which the sound waves are propagating.

➧ The SI unit of intensitywatt / m2.

➧ It is an objective quantity. As because we can define it with some numerical value.  Suppose the intensity of a sound is 5 watt m2 , the value is same for every person.

➧ In Physics the intensity of the zero decibel sound considered as the weakest intensity that is 10-12 Watt / m2.
[10-12 joules of energy passed through a unit area]

Characteristics of Sound - Intensity
Characteristics of Sound – Intensity


❂ Difference between Intensity and Loudness
Loudness Intensity
It is a Subjective quantity It is an Objective quantity
It is related to the Amplitude of Sound It is related to the energy passing through unit area
It is the degree of sensation of sound produced in the ear, That means it depends on the sensitivity of war. It does not depend on the sensitivity of the ear.
A Unit of Loudness is Decible (dB) Unit of Intensity is Watt / m^2

➧ Objective Vs Subjective Quantity

☛ Objective quantity is same for every person because it has a definite value and can be expressed with a unit.

☛ Example of objective Quantity is Decibel (dB) and intensity of sound ,  because both the term can be measured or represent with some numerical value, for example 100 dB and 5 watt / m2 respectively.

Subjective Quantity depends on a person, any sound can be loud for one person but not for other person.

☛ Example of Subjective Quantity is Loudness. It depends on the sensation of human ear for example, suppose loudness of a sound is 100 dB. Here the value 100 is same for ever person but the sound can be loud for one person but not for other person.


➧ It’s a characteristics of sound by which we can distinguish two sounds of same Loudness and same instrument but of different frequencies..
➧ In another words how the brain interprets the frequency of an emitted sound or the sensation of a frequency is called its pitch.
➧ Like Loudness, Pitch is also a subjective quantity.

◘  The Frequency of a sound wave is measured by the number of waves produced per unite time.
◘ A high pitch soundcorresponds to a high frequency sound wave.
◘ Similarly a low pitch sound corresponds to a low frequency sound wave.
◘ The SI unit of Frequency is Cycle per  Second or  Hertz (Hz). 1 Hzis equals to 1 cycle per Second.

Characteristics of Sound - Pitch
Features of Sound – Pitch

Quality or timber

➧  It is a characteristic of the Sound wave by which we can differentiate two sounds having Same Pitch and Loudness.
➧   The Quality or timber depends on the Waveform of the sound wave.
➧ The sound which is more pleasant is said to be of a rich quality. 

➧  A Single frequency (single cycle) sound  is called a Tone.
➧ A sound produced due to combination of several tones is called a Note.
➧ Noise is unpleasant to ear while music is pleasant to ear.

Music and Noise, both are closely related to the waveform produced by any musical instrument..

Music and Noise both are subjective quantity.
➧ The waveform of musical sound is Regular, Smooth, Continuousand Periodic.

➧ Whereas the wave form of noise is irregular, harsh, discontinous and non-periodic.

➧ Consider the following waveform (violin and Tuning fork) same frequency same amplitude but different waveform.

Characteristics of Sound - Quality or Timber
One of the Characteristics of Sound – Quality or Timber


Difference between – Amplitude, Pitch and Waveform (Infographics)

Characteristics of Sound - Amplitude, Pitch, Waveform
Characteristics of Sound – Amplitude, Pitch, Waveform

Top One Liner about the Characteristics of sound

1.The SI unit of Frequency?
Answer – Hertz (Hz)

2.What is the SI unit of Intensity?
Answer – Watt / m^2

3. The amount of energy passing through an unit area is called_
Answer – Intensity

4. Loudness is what type of quantity?
Answer – Subjective Quantity

5. Sound produced from two different musical instrument distinguished by its?
Answer – Quality or Timber

6. The waveform of a Noise is ?
Answer – irregular, harsh, and discontinuous

7.The Quality or Timber depends on ?
Answer – Waveform

8. Rich quality sound is said to be more __ ?
Answer – pleasant

9.Loudness is what type of quantity?
Answer – Subjective Quantity

10.Number of waveform produced per unit time is called _?
Answer- Frequency

11. High pitch sound corresponds to a -?
Answer – High frequency

12. The voice of male and female can be distinguished by -?
Answer – Pitch

13. What is the unit of loudness?
Answer – Decibel (dB)

14. Softest sound that can be heard?
Answer – 0 dB

15. What is the Intensity of the softest sound?
Answer – 10^ -12 watt / m^2

16. Name the characteristics of sound which depends on amplitude?
Answer:- Loudness

Source of this artice – NCERT

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