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