S OUND

O LD R IDDLE : If a tree falls in a forest and no one is there to hear it, does the tree make sound? What do you think?

H OW S OUND T RAVELS Through a medium Most common…air Sound: disturbance that travels through a medium in the form of a wave. Must have vibrations to have sound.

H OW SOUNDS ARE MADE Drum: surface begins to vibrate and creates a disturbance in the molecules. Molecules collide until they get to your ear Guitar Spring: string vibrates back and forth. Waves travel to your ear. Vocal cords: are like guitar spring. When you speak you force air through your voice box or larynx. Cords vibrate and send out waves to others ears.

S OUND IN SOLIDS AND LIQUIDS When you knock on a door Train tracks Ground to hear traffic Sound does not travel in space

S OUND B ENDS Just like when water waves hit something it spreads out, sound can spread out Going through a doorway Speed of sound depends on elasticity, density, and temperature of the medium

E LASTICITY Elasticity: ability of a material to bounce back after being disturbed. Rubber band vs. clay Sound travels faster in mediums with higher degree of elasticity.

D ENSITY Density: how much matter there is in a given amount of space. Depends on how close together particles are Sounds travels slower in more dense materials

T EMPERATURE Sound travels slower at lower temperatures & faster at higher temperatures

I NTENSITY Intensity: the amount of energy the wave carries per second through an area

L OUDNESS Sound waves with a higher amplitude have a greater intensity and more energy. The greater the intensity the louder the sound is. Loudness: what you actually hear

F REQUENCY When vocal cords are stretched vibrate more =higher frequency When vocal cords are relaxed vibrate less = lower frequency Frequency of sound wave: number of vibrations that occur per second Ultrasound: frequencies above the normal human hearing range Infrasound: frequencies below normal human hearing range.

P ITCH Pitch: how high or low the sounds seems. Depends on frequency of sound wave Tighter string=higher frequency=higher pitch Short string=higher pitch Glass with more water= lower pitch Less Water= higher pitch