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

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.

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

Intensity & Loudness loudness - human perception of the energy in a sound wave represented by the decibel (dB) scale more energy = higher amplitude = louder http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm

Frequency & Pitch pitch - how high or low a sound seems high frequency = high pitch [direct relationship] shorter, thinner vocal cords = higher pitch http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm

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

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 http://www.stmary.ws/highschool/physics/home/animations3/waves/DopplerEffectTrain.html

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