Published on March 9, 2014
What are the properties of sound? Chapter 12: Lesson 2:
Play a guitar. What do you hear?
Sound Is a type of energy we hear.
Vibrates Moves quickly back and forth.
Outer ear Inner ear Ear drum Middle ear
Sound Waves Vibrations that move through matter
Direction of sound Direction of energy
Sound waves moves in the same direction the energy is moving in. Longitudinal Waves
Waves that move in a different direction. Transverse Waves
Sounds travel through 3 media. - Sound travels through the solid the fastest (energy passed through closely packed particles) - Sound travels through the gases the slowest.
What is an echo? Echo are sound waves that are reflected back. (When the sound wave hits a flat, firm surface)
How can echo or noise be reduced? By covering the room with soft, thick, uneven material. Floor foam Wall padding Wood panels Wall art
How does covering rooms with the above materials help? When a sound wave hits the material the sound is absorbed (changes to thermal energy). Absorption: Transfer of energy when a wave disappears into a surface.
Frequency The number of times an object vibrates per second. Unit: Hertz (Hz).
Musical notes can be: High notes Low notes Pitch How high or low sound is.
Low pitch sounds has lower frequency. High pitch sounds has higher frequency.
Is there a difference between pitch and frequency? YES!!! Pitch is the way our ears hear sound. (The way we hear sound is related to the number of peaks BUT, they are not the same thing)
How to change pitch? High pitch Short guitar string Vibrates fast causing high pitch
Low pitch Long guitar string Vibrates slowly causing low pitch
If you are standing still the sound waves will sound normal
If the source of sound is moving towards you, you will hear more vibrations. So the sound you are hearing becomes high pitched.
If the source of sound is moving away from you, you will hear less vibrations. So the sound you are hearing becomes low pitched.
When sound frequency changes due to moving towards or away from the sound. The Doppler effect.
When you are TALKING the sound waves will look like this When you are SCREAMING the sound waves will look like this When you are WHISPERING the sound waves will look like this
Amplitude How dense is the air during compressions and rarefactions. Units: Decibels (dB)
Humans hearing range.
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