Reflection of Sound

The reflection of sound occurs when sound waves strike a solid or liquid surface and bounce back into the same medium. Reflection of sound requires a smooth or hard surface, which acts as a good reflector, while soft materials like curtains or carpets absorb sound and are considered bad reflectors. This principle is used in echo formation, soundproofing, and acoustic design.

There are two basic laws of reflection of sound:

• The angle of incidence is equal to the angle of reflection.
• The incident wave, the reflected wave and the normal all lie in the same plane.

• Horns, trumpets, loudhailers or megaphones are designed in such a way that sound can travel in a particular direction only without spreading out everywhere. This makes it easier for the audience to listen to the speaker. All these instruments work on the phenomenon of multiple reflections of sound.
• A stethoscope is a medical instrument used for listening to sounds produced within the body, mainly in the heart or lungs. In stethoscopes, the sound of the patient’s heartbeat reaches the doctor’s ears by multiple reflection of sound
• Generally, the ceilings of concert halls, conference halls and cinema halls are curved so that sound after reflection reaches all corners of the hall. Sometimes a curved soundboard may be placed behind the stage so that the sound, after reflecting from the soundboard, spreads evenly across the width of the hall.

1. Aim: To demonstrate the reflection of sound waves and verify that they follow the laws of reflection.

2. Requirements: Two identical cardboard tubes (long and sufficiently wide), ticking clock, table, and flat wall

3. Procedure

• Place the two cardboard tubes on a table as shown in the setup.
• Position the clock near the end of one tube.
• Place your ear at the end of the other tube and adjust the angles of the tubes until the ticking sound is heard clearly.
• Measure the angle of incidence (θ₁​) and the angle of reflection (θ₂​).
• Observe the relationship between these angles.

Reflection of sound

4. Conclusion: Sound waves get reflected from solid surfaces and obey the laws of reflection:

• The angle of incidence equals the angle of reflection (θ₁=θ₂​).
• The incident wave, the reflected wave, and the perpendicular to the surface lie in the same plane.
• Hard and flat surfaces act as good reflectors, while soft materials like cloth and curtains absorb sound and are bad reflectors.