Sound is a combination of low and high-pressure waves which is produced by a vibrating body. The vibration drives the particles in the propagation medium in oscillating motion, thus transmitting energy through the surrounding medium.
A sound wave is the sequence of disturbances created by the energy transmitting away from the sound’s source. The movement of the particles’ vibration is parallel to the direction of the wave propagation. So they are called longitudinal waves. When the atoms vibrate, they instantly move back and forth. This creates low pressure and high-pressure regions. These low-pressure regions and high-pressure regions are called rarefaction and compressions, respectively. This pair of regions are transferred to the surrounding space producing sound waves propagating from one physical medium to another.
Unlike electromagnetic waves, sound waves can only be transmitted through physical mediums like gas, liquid, and plasma as longitudinal waves (compression waves). Interestingly, it can be transmitted through solids as both transverse and longitudinal waves. The waves of alternating pressure variations from the stable pressure condition are the longitudinal sound waves (producing regions of rarefaction and compression). On the other hand, transverse sound waves are waves of varying shear stress perpendicular to the propagation’s direction.
The energy transferred by an oscillating wave transmits back and forth between the compression’s potential energy (longitudinal waves) or sideways displacement strain of the matter (transverse waves) and kinetic energy possessed by the moving particles of the medium.
The video explains the basic characteristics of a sound wave
The characteristics of sound propagation are usually impacted by three factors. There is a complicated correlation between the pressure and density of the given medium. This connection is impacted by temperature and determines the sound’s speed within the medium. The medium’s motion is another important factor of propagation. When the medium is in motion, then this motion may decrease or increase the average speed of the sound depending on the movement’s direction. When the sound waves and wind are travelling in the same direction, sound waves will have their propagation speed increased by the wind’s speed. On the flip side, if the wind and sound waves are propagating in opposite directions, then the speed of sound will decrease as the wind’s speed increases. The third crucial factor is the viscosity of the medium. The viscosity controls the rate at which the intensity of sound waves is reduced with time.
The speed of a sound wave is the distance covered per unit of time by this acoustic wave as it travels through a medium. At 20°C, the sound’s speed in air is around 343 m/s. It directly relies on the medium’s temperature as well as the type of medium through which the acoustic wave is moving. At 0°C, its speed is around 331 m/s.
Important Sound Wave Questions with Answers
1) What is meant by a sound?
Sound is a combination of low and high-pressure waves which is generated by a vibrating body. The vibration drives the particle in the propagation medium in vibrational motion, thus transmitting energy through the surrounding medium.
2) Sound waves are called mechanical waves. Why?
Mechanical waves are the type of waves that need a medium to transmit their energy from one region to another region. Sound strictly requires a medium and cannot propagate through vacuum.
3) Which is the medium through which sound waves move the fastest?
The sound waves move the quickest through solids.
4) Why do sound waves travel fastest in solids?
In solids, particles are more tightly packed than in gases and liquids. So particles inside them can easily collide with each other (comparatively). This enables sound to move fastest in solids as sound is just the collection of particle collisions.
5) Define the frequency of a sound wave.
The frequency of a sound wave is the number of compressions and rarefactions that happen per unit time.
6) Which is the medium through which sound waves move the slowest?
The sound waves move the slowest through gases.
7) What is meant by the reverberation of sound?
Reverberation occurs when the surrounding region is large and possesses numerous reflecting areas. Most familiar reverberating regions are large empty rooms and deep valleys.
8) What is the impact of temperature on the sound’s speed?
The speed of sound rises with the rise of the medium’s temperature. The speed in the air rises by 0.61 m/s when the air temperature increases by 10°C.
9) Which characteristic of sound differentiates a shrill or sharp sound from a dull or grave sound?
Pitch is the sound’s characteristic which differentiates a shrill or sharp sound from a dull or grave sound. It directly relies on the frequency. The higher the wave’s frequency, the higher is the pitch and the shriller the sound.
10) Why are sound waves called longitudinal waves?
The movement of the particles’ vibration is parallel to the direction of the wave propagation. So they are called longitudinal waves.
11) What are the main factors that control the characteristics of the propagation of sound?
There is an intertwining correlation between the pressure and density of the given medium. This relation is impacted by temperature and decides the sound’s speed within the medium. The medium’s motion is another significant factor in sound propagation. When the medium is in motion, this movement may decrease or increase the average speed of the sound depending on the movement’s direction. Another crucial factor is the viscosity of the medium. The viscosity controls the rate at which the intensity of sound waves is reduced as sound propagates from the source.
12) Define the speed of sound.
The speed of a sound wave is the distance covered per unit of time by this acoustic wave as it travels through a medium.
13) What is the speed of sound in air?
At 20°C, the sound’s speed in air is around 343 m/s. It directly relies on the medium’s temperature as well as the type of medium through which the acoustic wave is moving. At 0°C, its speed is around 331 m/s.
14) A _____ is the sequence of disturbances created by the energy transmitting away from the sound’s source.
Answer: sound wave
Explanation: A sound wave is the sequence of disturbances created by the energy transmitting away from the sound’s source.
15) The low-pressure regions and high-pressure regions are called _____ and _____, respectively.
Answer: rarefactions and compressions
Explanation: The low-pressure regions and high-pressure regions are called rarefactions and compressions, respectively.
16) Give an example of how the speed of the medium affects the propagation of sound.
When the sound waves and wind are travelling in the same direction, sound waves will have their propagation speed increased by the wind’s speed. On the flip side, if the wind and sound waves are propagating in opposite directions, then the speed of sound will decrease as the wind’s speed increases.
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Practice Questions
1) What is meant by a longitudinal wave?
2) What is meant by a transverse wave?
3) What is the speed of sound in vacuum?
4) What is a supersonic sound?
5) What is meant by the pitch of a sound?
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