Interactions of Sound Waves
Unit 2 Lesson 2
What affects the speed of sound?
• Two main factors that affect the speed of
sound:
– The type of medium the sound travels through
– The temperature of the medium
Medium & Temperature
• Medium:
Sound travels quickest through a solid, slower through a
liquid, and slowest through a gas.
– Why? The particles move when the sound travels through
the medium, so the wave is fastest when particles are
closest together.
• Temperature:
Sound travels quickest through a medium at higher
temperatures than lower ones.
- Why? The higher the temperature, the quicker the particles
in the medium are moving to transfer the sound.
How do sound and matter interact?
When sound waves hit a barrier, some sound waves may
bounce away from the front surface of the barrier, and some
sound waves may be absorbed or transmitted through the
barrier.
1. Matter can reflect sound waves.
-
Sound waves reflect best off smooth, hard surfaces.
-
Ex. Walls and Ceilings
2. Matter can absorb sound waves.
- soft materials absorb better than hard materials
-
Ex. Carpet acoustic tiles.
What is an echo?
An echo is an example of a reflected wave and depends
on the reflecting surface. Soft, rough, and irregular
surfaces reduce the strength of an echo.
Types of echoes:
1. Echolocation- animals use echolocation to
determine how far away an object is based on the
amount of time it takes the echo to return back to it.
2. Sonar- electronic echolocation used to locate
objects under water. (**sound navigation and ranging)
How do sound waves interact with
each other?
• Interference happens when two or more sound
waves overlap and combine to form one.
• 1. Constructive Interference- waves overlap and
combine to form a wave with a larger amplitude,
or height. (Louder sound)
– Ex. Sonic boom
• 2. Destructive Interference- waves combine and
form a wave with a smaller amplitude. (Softer
sound)
– Ex. Noise-canceling headphones.
What is Resonance?
• Resonance happens when a sound wave
matches the natural frequency of an object
and causes the object to vibrate.
– Every object has a frequency, or set of
frequencies, at which they vibrate at. (*Natural
frequencies.)
• Ex. When you feel the bass of loud music, resonance is
happening in your body.