What is Sound?
• Sound is a form of energy that 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 Characteristic 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.
What are the characteristics of sound waves?
◘ There are 4 major Characteristics of Sound these includes_
♦ 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 precept 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 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 a louder sound has higher energy.
Unit of Loudness
• 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, is considered Noise.
• Loudness is a subjective quantity, as because it varies from 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 the loudness of the sound we calculate the Intensity of the sound.
• The amount of sound energy passing per unit time through a unit area is 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. Because we can define it with some numerical value. Suppose the intensity of a sound is 5 watt m2. Here the value is the same for every person.
➧ In Physics the intensity of the zero decibel sound is considered the weakest intensity which is 10-12 Watt / m2. [10-12 joules of energy passed through a unit area]
Difference between Intensity and Loudness
|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 / m2|
➧ Objective Vs Subjective Quantity
☛ Objective quantity is identical for every person because it has a definite value and can be expressed with a unit.
☛ An example of objective Quantity is Decibel (dB) and intensity of sound because both the term can be measured or represented 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 another person.
☛ An example of Subjective Quantity is Loudness. It depends on the sensation of the human ear, for example, suppose the loudness of a sound is 100 dB. Here the value 100 is the same for every person, but the sound can be loud for one person but not for other people.
☛ It’s a characteristic of sound by which we can distinguish the two sounds of the same Loudness and instrument but of different frequencies.
☛ In other 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 unit of time.
☛ A high pitch sound corresponds 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 Hz is equal to 1 cycle per Second.
Quality or timber
☛ It is a characteristic of the Sound wave by which we can differentiate two sounds having the Same Pitch and Loudness.
☛ The Quality of timber depends on the Waveform of the sound wave.
☛ The sound which is more pleasant is said to be of rich quality.
☛ A Single frequency (single cycle) sound is called a Tone.
☛ A sound produced due to a combination of several tones is called a Note.
☛ Noise is unpleasant to the ear while music is pleasant to the ear.
☛ Music and Noise, both are closely related to the waveform produced by any musical instrument..
☛ Music and Noise, both are subjective quantities.
☛ The waveform of musical sound is Regular, Smooth, Continuous, and Periodic.
☛ Whereas the waveform of noise is irregular, harsh, discontinuous, and non-periodic.
➧ Consider the following waveform (violin and Tuning fork) same frequency same amplitude but a 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 a unit area is called_
Answer – Intensity
4. Loudness is what type of quantity?
Answer – Subjective Quantity
5. The Sound produced from two different musical instruments distinguished by theirs?
Answer – Quality or Timber
6. The waveform of a Noise is?
Answer – irregular, harsh, and discontinuous
7. The Quality of Timber depends on?
Answer – Waveform
8. The Rich quality sound is said to be more __?
Answer – pleasant
9. Loudness is what type of quantity?
Answer – Subjective Quantity
10. Number of waveforms produced per unit of time is called _?
11. High pitch sound corresponds to a -?
Answer – High frequency
12. The voice of males and females 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?
Frequently Asked Questions (FAQ) on Characteristics of Sound
Answer: The 3 main characteristics of sound are Pitch. Height and quality.
Answer: The loudness is related to Amplitude.
Answer: Two different musical instruments
Source of this article – NCERT