1. Unit 5 Waves
Ch. 21 Sec. 1 & 2
What is Sound?

2. Sound Waves
sound - a compressional wave caused by vibrations that make air molecules move back & forth
a sound wave is a series of compressions (dense air molecules) & rarefactions (spread out air molecules)
speed of sound is…
fastest through solids
slowest through gases
faster at high temps.
slower at low temps.

3. Human Ear 3 Main Parts: outer ear - collects sound
middle ear - amplifies sound when vibrations of the eardrum are passed to 3 small bones
inner ear - converts sound when vibrations are passed to cells in the cochlea and then create nerve impulses which travel to the brain 
disease, age, & exposure to loud sounds damage hearing

4. Intensity & Loudness
loudness - human perception of the energy in a sound wave
represented by the decibel (dB) scale
more energy = higher amplitude = louder

5. Frequency & Pitch pitch - how high or low a sound seems
high frequency = high pitch [direct relationship]
shorter, thinner vocal cords = higher pitch

6. Echoes echo - a sound wave reflected off a hard surface
can be used w/ sonar to map the ocean floor
can be used w/ echolocation to navigate & hunt

7. The Doppler Effect
Doppler effect - change in frequency that occurs when a sound source or listener is in motion
ex. as a siren approaches, higher frequency causes a higher pitch
ex. as a siren passes, lower frequency causes a lower pitch

8. Using Sound in Medicine
sound waves can be used in medicine…
can view body parts
ultrasounds can destroy kidney stones
can view developing fetuses