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
➧ 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.
♦ 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.
Intensity
➧ 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 intensity – watt / 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]
| ❂ 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.
Pitch
➧ 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.
➧ Frequency
◘ 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.
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.
Difference between – Amplitude, Pitch and Waveform (Infographics)
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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