Reflection of Sound

Reflection of Sound is the phenomenon of striking of sound with a barrier and bouncing back in the same medium. It is the most common phenomenon observed by us in our daily life. Let’s take an example, suppose we are sitting in an empty hall and talking to a person we hear an echo sound which is created by the reflection of the sound.

Sound is the form of the wave that gets reflected after striking the hard surface and it follows the law of reflection of the wave.  Sound travels through a medium it can travel through solids, liquids, and gases. Unlike other waves like light waves, and others sound can not travel through a vacuum it requires a medium to travel.

Let’s understand more about sound, its reflection, and others in detail in this article.

Sound Definition

Sound is a form of energy like light energy and heat energy. Sound is a wave made of vibrations in the air. These vibrations create sound waves which move through mediums such as solid, liquid, or gas, before reaching our ears. Sound does not travel in a vacuum. Sound, therefore, is not audible in space. Just like light, the sound gets reflected at the surface of a solid or liquid. This bouncing back of sound when it strikes any surface is the reflection of sound. 

Important properties to better understand the reflection of sound are,

Reflection of Sound Waves

The bouncing back of the sound wave on striking a surface such as a wall, metal sheet, plywood, etc. is called the reflection of the sound wave.

Reverberation

If the distance is less than 17 m, then the original sound mixes with the reflected sound. Due to repeated reflections at the reflecting surface, the sound gets prolonged. This effect is known as reverberation.

Echo

An echo is the reflection of sound heard by us. If the distance is lesser than 17 m we hear an echo.

Characteristics of Sound

Various characteristics of the sound are,

Loudness

It is the property by virtue of which a loud sound can be distinguished from a faint one, both having the same pitch and frequency. Loudness is expressed in a unit called decibel (dB). It is directly proportional to the amplitude of the vibration.

Intensity

The amount of sound energy passing each second through a unit area is called the intensity of sound.

Pitch

Pitch is that characteristic of sound by which an acute (or shrill) note can be distinguished from a grave or flat note. It is not the same as frequency. It refers to the sensation as perceived by the listener.

Quality / Timbre

The quality or timbre of the sound is that characteristic that enables us to distinguish one sound from another having the same pitch and loudness but emitted by two different instruments.

Factors Affecting Loudness of Sound

Factors affecting the loudness of the sound are,

Loudness of the sound is directly proportional to the square of the amplitude of the sound wave.

Loudness ∝ (Amplitude)²

Loudness of the sound is inversely proportional to the square of the distance between the source of the sound and the observer of the sound.

Loudness ∝ 1/(Distance)²

Some other factors influencing the loudness of the sound are,

• Loudness depends on the surface area of the vibrating body. 
• The larger the vibrating area the louder the sound is heard. Loudness depends on the density of the medium. 
• The more the density of the medium more the loudness. Loudness depends on the presence of resonant bodies. 
• The presence of resonant bodies near the vibrating bodies increases the loudness

Learn more about Characteristics of Sound Waves

Reflection of Sound

Bouncing back of sound waves after striking from the hard surface is called reflection of sound or we can say that sound traveling in a given medium after striking the surface of another medium returns in the same medium, which is called reflection of sound.

The reflection of sound is similar to the reflection of light as it also follows the laws of reflection of waves. As a sound wave travels across a room and touches a wall, a reflective wave is produced that will reintroduce a portion of that wave back into the room.  

An obstacle is necessary for the reflection of sound. The reflection of sound waves is also affected by the shape of the surface. Various terminology used in the reflection of sound is,

Incident Sound Waves

The sound waves that travel toward the reflecting surface are called incident sound waves. The angle formed by the incident sound waveforms with the normal to the surface is called the angle of incidence.

Reflected Sound Waves

Sound waves that return from the reflecting surface are called reflected sound waves. The angle formed by the reflected sound waveforms with the normal to the surface is called the angle of reflection.

Laws of Reflection of Sound

Similar to the laws of reflection of the wave. We have laws of reflection of sound. The basic Laws of Reflection of Sound are,

• The angle of reflection of the sound wave is always equal to the angle of incidence of the sound wave. (Angle of Reflection = Angle of Incidence)
• For sound waves, the incident wave, the reflected wave, and the normal at the point of incidence lie on the same plane.

Applications of Reflection of Sound

Reflection of sound has many applications some of the important applications of the reflection of sound are,

Echo 

Echo is the repetition of a sound caused by the reflection of sound waves. Echo arrives at the listener with a delay after the direct sound. If the gap between the original sound wave and the reflected sound wave is greater than 1/10^th of the second, the reflection is called an Echo.  

Bats and Dolphins use echo to detect obstacles. Echo is also used in the SONAR (Sound Navigation And Ranging) technique used for the detection and location of objects inside the water, such as submerged submarines, and icebergs.

An echo is heard only if the distance between the person producing the sound and the rigid obstacle (or reflector) is long enough to allow the reflected sound to reach the person at least 0.1 seconds after the original sound is heard.

Conditions for Hearing Echo Distinctly

The minimum distance in air between the source of sound and the reflector must be 17 m. The size of the reflector must be large enough as compared to the wavelength of the sound wave. The intensity of sound should be sufficient so that the reflected sound reaching the ear is audible.

Stethoscope

A stethoscope is a medical device that is used to hear the sounds of the internal organs of a patient. The sound coming from the heart is of low intensity and when it passes through the pipe of the stethoscope it undergoes multiple reflections and hence amplify the sound to make it audible.

Megaphone

Megaphones is a device which is used to increase the intensity of the sound it prevents the spreading out of sound waves by successive reflections, thus confining them to the air in the tube.

Soundboard

Soundboards are curved surfaces that are placed in such a way that the sound ways from the sound source are at the focus of the board increasing the intensity of the sound at a particular point.

The cinema hall and auditorium are made keeping the above concept in mind.

Hearing Aid

A hearing aid is a device that is used by people who are unable to hear normal sounds. A hearing aid has a microphone that allows the sound from the environment to enter, then the sound goes to the amplifier which amplifies with multiple reflections and the speaker allows the sound to exit the device and enter into the person’s ear.

Read More,

• Production and Propagation of Sound
• Refraction of Sound
• Speed of Sound
• Wavelength of sound wave

FAQs on Reflection of Sound

Q1: What is Sound?

Answer:

Sound is defined as the form of energy which enable us to hear. It is a mechanical wave produced by the disturbance created in the surrounding medium.

Q2: What are the Laws of Reflection of Sound?

Answer:

The laws of reflection of sound are,

• Angle of Reflection of sound wave is always equal to angle of incidence of the sound wave.
• The reflected sound wave, the incident sound wave, and the normal to these waves belong in the same plane.

Q3: Can Sound Travel in Space?

Answer:

No, sound cannot travel through space as it needed any medium such as solid medium, liquid medium, or gaseous medium to propagate.

Q4: How do Astronauts Communicate with each other in Space?

Answer:

As we know that sound waves do not travel through a vacuum, astronauts use radio waves to communicate with each other.

Q5: What is an Echo?

Answer:

Echo is defined as the repetitive sound heard after reflections from a rigid surface such as a cliff or a wall. The condition necessary for the production of echo is that the distance between the source and the observer should be greater than 17 m.

Q6: What is the Intensity of Sound?

Answer:

The amount of energy carried by the sound wave passing through a unit area is defined as the intensity of the sound wave.

Q7: What is the Speed of Sound in Air?

Answer:

The speed of sound in air is approximately 332 m/s. The speed of sound in the air can vary according to the pressure and the temperature of the air.

Q8: How does Sound Produced by a Vibrating Object reach your Ear?

Answer:

Sound is a form of a wave which travels through a medium, so the sound produced by a vibrating object reaches are ear through any medium such as solid, liquid or gas.