Diffraction uses the edges of a barrier as a secondary sound source that sends waves in a new direction. You hear your friend because of sound diffraction. Instead, it must be going around the corner and out the door. Because you would not hear your friend if the door was closed, sound is not traveling through the wall. Since sound travels in a straight path from its source, how does it get around corners? You already know that if you and your friend are standing on either side of a wall and there is an open door nearby, you will be able to hear what your friend says. How does sound reach every point in the room? The energy lost as heat is too small to be felt, though, it can be detected by scientific instruments. The best absorptive material is full of holes that sound waves can bounce around in and lose energy. By the time the thunder has reached you, all the high pitches are lost and only the low ones can be heard. This is because air absorbs high frequencies more easily than low. When the storm is farther away, you hear a low rumble instead. When you are very close to a storm, you hear thunder as a sharp crack. One example of air absorbing sound waves happens during a thunderstorm. Sound AbsorptionĮverything, even air, absorbs sound. A wave has some of its energy absorbed by the objects it hits. A sound wave will continue to bounce around a room, or reverberate, until it has lost all its energy. The sound you hear ringing in an auditorium after the band has stopped playing is caused by reflection off the walls and other objects. Echoes are the sound of your own voice reflecting back to your ears. Reflection is responsible for many interesting phenomena. No one in the rest of the room will hear anything. If your friend stands at one focus and you stand at the other, his whisper will be heard clearly by you. A whispering gallery is designed as an ellipse. Sound will travel from one focus to the other, no matter where it strikes the wall. If the parabola is closed off by another curved surface, it is called an ellipse. Many stages are designed as parabolas so the sound will go directly into the audience, instead of bouncing around on stage. The following two videos cover the features of sound as they propagate into a different medium, alongside other sound waves or around corners.When sound reflects off a special curved surface called a parabola, it will bounce out in a straight line no matter where it originally hits. Wave superposition occurs when two or more sound waves are travelling through the same medium at the same time, the net displacement at any point in time, is simply the sum of the individual wave displacements. R esonance is the tendency of a system to vibrate with increasing amplitudes at unique frequencies of excitation. Diffraction is the bending of sounds waves around obstacles and openings. Reflection of sound waves occurs when it strikes the surface of another medium and bounces back in some other direction, causing echoes more than 0.1 seconds after the original sound wave was heard.
In this post, we conduct investigations to analyse the reflection, diffraction, resonance and superposition of sound waves, as a part of the Prelim Physics course under the module Waves and Thermodynamics and sub-part Sound Waves. What is reflection, diffraction, resonance and superposition in term of sound waves? Latent Heat Involved in a Change of State.Relationship between the Change in Temperature of an Object and its Specific Heat Capacity (Q = mc△T).Relationship Between the Temperature of an Object and Kinetic Energy.Applying Equations and Relationships to Solve Questions (Refraction Index, Snell's Law, Critical Angle, Intensity of Light).Relationship Between the Inverse Square Law, the Intensity of Light and the Transfer of Energy.Practical Investigation: Phenomenon of the Dispersion of Light.Refraction and Total Internal Reflection.Practical Investigation: Formation of Images in Mirrors and Lenses.
Behaviour of Standing Waves on Strings and Pipes.Reflection, Diffraction, Resonance and Superposition of Sound Waves.