When you hear “reflection,” you immediately think of light. You might wonder that can sound waves be reflected? And what is the reflection of sound? Go through the article in detail to find these answers.
Sound, just like light, is a kind of energy. The energy is carried in the form of a wave. Both light waves and sound waves have some common traits, such as reflection, refraction, and diffraction.
When can sound waves be reflected?
Sound, a mechanical wave, follows the same reflection rules as light.
It is simply referred to as “reflection of sound” when sound bounces back off of any polished or unpolished surface. In other words, sound reflection occurs when a sound wave travels through one medium and then strikes the surface of another, returning in the opposite way.
Laws of reflection of sound waves:
- The angle of the reflection in the case of sound reflection will be the same as the angle of incidence.
Where, 𝛉i = Angle of incidence
𝛉r = Angle of reflection
- The plane from which the sound is being reflected will be the same as the plane from which the incident and normal sound are produced.
As a result, we can deduce that light and sound waves both obey the same laws of reflection.
The difference is that for the reflection of sound, unlike light, it is not necessary to have a polished surface. Sound can be reflected from any rough surface too. Thus, it just requires any surface or obstacle to be reflected back. Furthermore, the shape of the surface from which the sound is reflected influences sound reflection.
Let’s think about an illustration:
Let’s say you throw a ball at a wall, and it bounces right back at you. Now that you are lighting the wall with the torch, you are experiencing the phenomenon of light reflection. The same thing happens when you speak close to a wall—you hear what you just said. Yes, your guess is correct; it is nothing more than a reflection of sound.
When you speak, sound waves are produced, and when you hear them back, sound waves of audible frequency are reflected back from the surface of the wall. As a result, sound reflection is responsible for making you hear your own sound.
Now, let us consider the reflection of sound waves from different surfaces.
Reflection of sound on different surfaces:
Sound reflection will also depend on the surface type, such as whether it is rarer or denser. If the sound is reflected from a denser material, then just a 180-degree phase change takes place. However, when reflected from a rarer medium, the compression is reflected as rarefaction, and vice versa. Let’s get into it in more detail.
Reflection of sound on hard surfaces OR rigid boundaries:
Due to the compression and rarefaction that make up sound waves, their areas alternate between high and low pressure. Compression and rarefaction are terms used to simultaneously describe the region of high and low pressure. As a result, sound waves are a sort of pressure wave as well.
Consider a sound wave (pressure wave or longitudinal wave) traveling through the air and colliding with a hard surface such as a wall. Now, when the sound wave’s compression impinges on a hard surface, it essentially tries to push the wall by applying force. However, because the wall is a hard surface, it pushes the compression formed in the air due to sound in the opposite direction by applying an equal and opposite force.
As a result, compression that was moving in the right direction will now move in a leftward direction. As a result, the displacement of the medium particle during incidence and reflection will be in the opposite direction. As a result, if we consider the phase difference between the incident and reflected sound waves, it becomes 𝜋 radian, or 180°.
The approach will be the same if we now take the instance of rarefaction into consideration. The rarefaction caused by the incident will be reflected as rarefaction.
The wall serves as an example, which we have already seen. Since the wall’s surface is hard, your sound is reflected off of it when you talk.
Reflection of sound waves from rarer medium:
Think about a longitudinal sound wave that is traveling through a denser or solid medium and hitting the interface or boundary of a rarer media. When the incident sound wave’s compression collides with a boundary made of a rarer material, force is applied to that surface. Since the rarer medium’s surface has less resistance and the compression of the sound wave contains high pressure, the rarer medium’s boundary will be pushed back.
In contrast to the denser media, particles in the rarer medium are free to migrate. Therefore, rarefaction is produced at the intersection of the two mediums. Therefore, incident compression returns as rarefaction after reflection from the surface of the rarer material. As a result, no phase change is noticed when a sound wave from a denser medium is reflected from a rarer medium.
The same thing will happen if rarefaction occurs on the surface of a rarer medium and reflects back as compression.
As an illustration, imagine sound traveling through a pipe that is filled with water. Now imagine that air is present at the pipe’s open end. And we already know that water is a denser medium for sound than air. As a result, high pressure causes the air molecules in the surrounding area to move away quickly when compression occurs at the water-air interface. As a result, compression will be converted into rarefaction before being reflected.
Reflection of sound waves from curved surface:
As we have seen, different surfaces reflect sound differently. In a similar manner, the curvature of the surface affects how the sound reflects. The curvature of the surface has the ability to change the intensity of the sound.
Curved surfaces are classified into two types:
- Concave surfaces and
- Convex surfaces.
Now let us consider it thoroughly.
Reflection of sound from concave surface:
When sound waves hit a concave surface, the reflected waves converge, much like they do with light waves. Additionally, reflected waves likewise had a single point of focus. As a result, the intensity of the reflected sound wave increases as it reflects from the concave surface.
This phenomenon is used in the natural world as well. From the recent scientific research, we have come to know two facts:
- A bull moose may use his antlers as a satellite disc with which it can gather and focus sound easily.
- As per deep research and long thoughts by scientists, the owls’ facial disks are spherical and can be easily moved to collect and then reflect sound towards their ears.
Even though it occurs in nature, we often stay away from concave surfaces when trying to reflect sound. The reason for this is that focusing on the geometrical center of the surface will result in a loud hotspot within a space. As a result, long-distance reflected sound transmission will be unusual.
If a concave shape is necessary, sound-absorbing materials will probably need to be used. You might be able to reduce noise issues by modifying your curve’s geometry with the help of an acoustic specialist. The theater is making use of this phenomenon.
In terms of maintaining the intensity of the reflected sound, concave surfaces are typically employed in front of speakers in theaters. However, as we already stated, it produced a loud hotspot, which is why noise or abnormal sound is reflected. The theater’s walls and ceiling are constructed of noise-absorbing materials to reduce this noise. As a result, both techniques enhance one another by reducing the amount of error that remains.
Reflection of sound from convex surface:
When sound waves are incident on the convex surface, the reflected sound will diverge out in each possible direction. As the sound diverges, obviously, the intensity of sound decreases.
Diffusion of the sound from the convex surface helps the musical blend spread out in all directions and avoid unwanted reflections.
Various geometries help in sound diffusion, which includes:
- Hemisphere or half cylinder
- Surface with various angles like saw tooth pattern
Other significant phenomena associated with reflection of sound:
The reflection of the sound causes echo and reverberation to occur. However, there are some differences between the two phenomena. Let’s talk about it.
The term echo refers to the repeated hearing of reflected sound. An echo can be heard when a sound is reflected in a large space.
Any huge space can create an echo, including both open and closed spaces. The distance between the source and the reflecting body needs to be greater than 50 feet in order to hear the echo effectively. Because of the relatively long distance, there will be a time delay between audible sounds. We can therefore hear two or more distinct sounds.
Think of yourself as standing in a big empty room and loudly talking “Hello”. Then Due to the reflection of sound in a large area and through the hard surface, you hear the word hello repeatedly like “Hello,”…..”Hello,”…..”Hello”. The sound will go out into the room and be reflected from the walls to your ears. The more time it takes for the sound to reach your ear, the more disturbing it becomes.
You may have done this while vacationing in a hill station by shouting your name in the hills. You might have noticed that echo also occurs during the cross-talks in the phone calls.
When the distance between the source of the sound and the reflecting surface is very small, the original sound is mixed with the reflected sound. As a result of the overlapping of various sounds, the persistence or continuous sound is produced. This is referred to as reverberation.
You may have overheard these if you have spoken in a huge dome, auditorium, or hall. As a result of the various reflections of sound in these types of locations, the reflected sounds often blend with the original sound. You often need to hear the reverberation effect if these reflections occur within 50 milliseconds or 0.05 seconds.
Applications of the reflection of sound:
The property of the sound to be reflected is being used to make our lives easier. The following are the applications of the reflection of sound:
- Stethoscope: The stethoscope used by doctors operates on the theory of reflection of sound. The doctor uses it to listen to the patients’ heartbeats. Due to various reflections of the sound occurring inside the stethoscope, the patient’s heartbeat can be heard clearly by the doctor.
- Hearing aid: Another medical device that takes advantage of the reflection of sound principle is the hearing aid. People who have trouble hearing use this device. Sound is reflected in a slimmer region in that device so that it can be directed towards the ears with a high level of intensity.
- Sonar: Yes, the theory of sound reflection also applies to sonar. The device that uses the reflecting signal to calculate the distance and speed of underwater objects is called a sonar. It is employed in ships to identify any threats to the ship to avoid tragic accidents like the Titanic. The Navy also employs it to find mines and submarines.
- Soundboard: Soundboards are simply curved surfaces that are positioned in such a way that the source of the sound remains in focus. They evenly reflect the sound waves throughout the room or auditorium. As a result, employing a soundboard improves sound quality.
- Megaphone: Multiple reflections are also used in a megaphone. It has a funnel-like form. As a result, when sound is produced inside the megaphone’s funnel, the waves are reflected many times before moving along the path that leads to the funnel’s opening. As a result, the sound’s amplitude increases at its beginning.
We hope that this article has given you all the information you need to know about the reflection of sound waves in a useful way. Please visit our website to read more science-related articles like this one.