Waves and SoundWaves and Sound

Sound is a compression wave.Sound is a compression wave. Sound needs a medium to travel through.Sound needs a medium to travel through.

-Faster through solids, slowest in -Faster through solids, slowest in

gases.gases.

-Faster in warm air than cold.-Faster in warm air than cold.

Light travels faster than sound.Light travels faster than sound.

Supersonic is faster than sound.Supersonic is faster than sound.

Normal humans can:Normal humans can:

- hear sounds between 20Hz – 20,000Hz- hear sounds between 20Hz – 20,000Hz

- Ultrasonic is sound above 20,000Hz- Ultrasonic is sound above 20,000Hz

- bats, dogs, whales- bats, dogs, whales

- Ultrasound (medical & construction)- Ultrasound (medical & construction)

- Infrasonic is sound below 20Hz- Infrasonic is sound below 20Hz - Thunder that is felt and not heard.- Thunder that is felt and not heard.

- Rumble of heavy construction equipment.- Rumble of heavy construction equipment.

SONARSONAR

SOSOundund

NNavigationavigation

AAnd nd

RRanginganging

- Using sound waves to find size and - Using sound waves to find size and depth below water.depth below water.

SonarSonar

LoudnessLoudness

Loudness is a human perception of Loudness is a human perception of intensity.intensity.

Is measured in decibels. (dB):Is measured in decibels. (dB):0 dB 0 dB - faintest whisper- faintest whisper

20 dB 20 dB - rustling leaves- rustling leaves75 dB75 dB - vacuum cleaner- vacuum cleaner

120 dB120 dB - threshold of pain- threshold of pain 150 dB150 dB - jet taking off- jet taking off

The Doppler EffectThe Doppler Effect When sound is moving closer to you, the When sound is moving closer to you, the

waves are compressed making waves are compressed making frequency higher.frequency higher.

When sound is moving away from you, When sound is moving away from you, the waves are rarefied, making frequency the waves are rarefied, making frequency lower.lower.

Noise PollutionsNoise Pollutions

… … is displeasing human or machine created sound is displeasing human or machine created sound that that

disrupts the disrupts the environmentenvironment.. The dominant form of noise pollution is from The dominant form of noise pollution is from

transportation sources, principally transportation sources, principally motor vehiclesmotor vehicles. The . The word "noise" comes from the Latin word word "noise" comes from the Latin word nauseanausea meaning "meaning "seasicknessseasickness", or from a derivative (perhaps ", or from a derivative (perhaps Latin Latin noxianoxia) of Latin ) of Latin noceōnoceō = "I do harm", referring = "I do harm", referring originally to nuisance noise.originally to nuisance noise.

DiffractionDiffraction

..is the bending of waves around barriers...is the bending of waves around barriers.

(This is how we can hear around corners.)(This is how we can hear around corners.)

Lightning rule:Lightning rule:

- Thunder always occurs after lightning.- Thunder always occurs after lightning.

- Storm is one mile away for every 5 sec - Storm is one mile away for every 5 sec

difference.difference.