1. Waves and Sound

2.  Sound is a compression wave.  Sound needs a medium to travel through. -Faster through solids, slowest in gases. gases. -Faster in warm air than cold. -Faster in warm air than cold. Light travels faster than sound. Supersonic is faster than sound.

3.  Normal humans can: - 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.

4. SONAR  SO und  N avigation  A nd  R anging - Using sound waves to find size and depth below water.

5. Sonar

6. Loudness  Loudness is a human perception of intensity.  Is measured in decibels. (dB): 0 dB - faintest whisper 20 dB - rustling leaves 20 dB - rustling leaves 75 dB- vacuum cleaner 120 dB- threshold of pain 120 dB- threshold of pain 150 dB- jet taking off 150 dB- jet taking off

7. The Doppler Effect  When sound is moving closer to you, the waves are compressed making frequency higher.  When sound is moving away from you, the waves are rarefied, making frequency lower.

8. Noise Pollutions … is displeasing human or machine created sound that disrupts the environment. disrupts the environment.environment The dominant form of noise pollution is from transportation sources, principally motor vehicles. The word "noise" comes from the Latin word nausea meaning "seasickness", or from a derivative (perhaps Latin noxia) of Latin noceō = "I do harm", referring originally to nuisance noise. motor vehiclesnauseaseasicknessmotor vehiclesnauseaseasickness

9. Diffraction ..is the bending of waves around barriers. (This is how we can hear around corners.)

10.  Lightning rule: - Thunder always occurs after lightning. - Storm is one mile away for every 5 sec difference. difference.