What are the

properties of sound?

Chapter 12: Lesson 2:

Play a guitar.

What do you hear?

Is a type of energy we hear.

Sound

Moves quickly back and forth.

Vibrates

Compression

Rarefaction

Outer ear

Middle ear

Inner ear

Ear drum

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.

Wall paddingFloor foam 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

How high or low sound is.

Pitch

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.