SOUND

Sound is a mechanical
wave (requires a medium
to travel) and a
compressional/ longitudinal
wave (molecules colliding).

Compressions
The close-together part of the wave
Rarefactions
The spread-out parts of a wave

Waves transfer energy
without transferring matter.

In which media does sound
travel fastest?
 Sound travels better through high-density
materials
 The closer the molecules are together, the faster they
can collide and transfer energy

Hearing and the Human Ear

Properties of Sound

Pitch
-description of how high or low
the sound seems to a person
Loudness
how loud or soft a sound is
perceived to be.

Loudness of Sound in Decibels
Sound Loudness
(dbs)
Hearing
Damage
Average Home 40-50
Loud Music 90-100 After long
exposure
Rock Concert 115-120 Progressive
Jet Engine 120-170 Pain

KINDS OF SOUND WAVES
1. AUDIBLE SOUND
- human ear can hear
( 20 – 200 000 Hz)
2. ULTRASONIC WAVES
above 20 000 Hz
- Cannot be detected by human ear but some
animals do.
- Dogs can detect as high as 50 000 Hz and bats
can hear up to 100 000 Hz.
- Uses in ULTRASOUND

- Sound below 20 Hz.
SOURCES OF INFRASOUND:
- Vibrating heavy machines
- Earthquakes
- Thunder
- Volcanoes
- It cannot be heard by human ear but can cause
damage.
3. INFRASOUND WAVES

The range of hearing,
singing, and the quality of
notes.

 Sound is produced when an object
vibrates.
 When an object vibrates it exerts
a force on the surrounding air
 Loudness of a sound is recorded in
decibels
 As a sound gets louder, the
amplitude of the wave increases.

The moving air mass carries the
sound of the vibration to your ear.
 The air is the MEDIA that it travels
through.
 Medium is what the wave travels
through (ex. solid, liquid, gas)
 NO MEDIUM NO SOUND!!!!

Self Check!