Physical Science

Sound

Vibration – anything that moves up and down, back and forth, side to

side

(a wiggle in time)

Wave – A wiggle in both space and time

Image from Yahoo images

• Wavelength – distance from one crest to the next

• Amplitude – distance from the midpoint to the crest

• Frequency – the number of crests passing a stationary point in a given amount of time

(usually hertz (Hz) – cycles per second)

Radio station Frequencies

• AM – 650 kilohertz – 650,000 cycles per second

• FM – 97.5 megahertz – 97,500,00 cycles per second

Reflection of Sound

sound reflects in the same way that light does. If a mirror is turned so that you can see an instrument, sound will also be reflected toward you

How to build a home theater

speaker

mirror

Refraction of Sound

• sound travels faster in warm air than in cold air. Sound near the warm air close to the ground will move faster and the sound wave will bend. Sound doesn’t seem to carry as well

Resonance - means resounding or sound again

Beats

Doppler Effect

Doppler Effect

• The sound will have a higher pitch (frequency) as the siren in coming toward you and a lower pitch (frequency) as it moves away

Sonic Boom

• The sound waves stack up like a water wave in front of a boat. When the wave hits your ears, it is a very large sound wave

Image from: http://en.wikipedia.org/wiki/Sonic_boom Image from yahoo images