4.4 Sound

Sound is a __ wave & is l__

mechanical, longitudinal

What is the line?

compression

What is the line?

rarefaction

Humans w/ good hearing can hear sound from __Hz → __ Hz

20, 20000

The Human Ear
Sound waves → outer ear → ear canal → eardrum: v__ bone of middle ear → cochlea (i__ ear)

vibrates, inner

Hair cells in the c__ move & convert sound vibrations → e__ signals
> these signals go to the b__ via hearing nerve

cochlea, electrical, brain

Older = cochlea hair cells lose f__
> most adults >50yrs cant hear freq >__Hz

flexibility, 12000

Ear bones are s__ and easily damaged by loud sounds & can’t be r__

small, repaired

Define ultrasound

sound at freq >20000 Hz

Ultrasound examples
> bats use e__ to see the world
> s__: on ships; calculates depth of shoal of f__
> medical scanning tissues & foetus

echolocation, sonar, fish

Define infrasound

sound at freq <20Hz

Pitch is based on

freq

Short λ = __ freq = __ pitch

high, high

High λ = __ freq = __ pitch

low, low

Loudness is based on

amplitude

What is loudness measured in?

decibel

>  Sound <75dB is safe w/ no damage
>  Sound >__dB causes damage within 15min

100

Define echo

reflection of sound waves

Experiment: Speed of Sound

1. 2 ppl stand __m apart
2. A c__
3. B s__ stopwatch when clap is s__
B s__ stopwatch when clap is h__
4. v=__

100, claps, starts, seen, stops, heard, d/t