Sound Waves

What is Sound?

• Sound is caused by a vibration of atoms in pulses. Each sound wave pulses with a certain frequency. The vibration pulse causes areas of compressions and rarefactions in the atoms of the medium.

• http://www.youtube.com/watch?v=J2BUvWRCBGM• Sound is a longitudinal /compressional wave, which is a

type of mechanical wave. • Sound waves can be caused by transverse waves such as

those produced when you pluck or strum a guitar string. The energy in the transverse wave is transferred into a longitudinal wave; each crest creates an area of compression in the air around the string.

• http://www.youtube.com/watch?v=TKF6nFzpHBU

Anatomy of a Sound Wave

Properties and Observations

•Speed

•Wavelength

•Frequency

•Amplitude

•Pitch

•Loudess

Speed of Sound

•Sound waves travel the best in solids and worst in air.

•The closer together the atoms are, the faster the sound will travel.

•Sound will not travel in a vacuum, such as space because there is no matter/medium for the wave to vibrate.

Pitch

•Pitch is determined by frequency.

•The higher the frequency the higher the

pitch.

•Each pitch as a set frequency therefore to

change pitch one must change

wavelength or speed.

Loudness

•Loudness is a result of amplitude of the sound wave.

•The more energy you put into the sound wave the higher the amplitude and the louder the sound.

•The high the amplitude the louder the sound. This is why amplifiers make sound louder.

Relationships Between Wave PropertiesSpeed Wavelengt

hFrequency Pitch Amplitude Loudnes

s

Wavelength and Frequency

•Since speed is controlled by the medium the wave is travelling through:

•When the speed is constant (no change in medium) in order for pitch to change the frequency must change, in order to change frequency the wavelength must change. ▫As wavelength increases frequency

decreases, which causes pitch to decrease. ▫As wavelength decreases frequency

increases, which causes pitch to increase.

Medium and Frequency•When the medium in which the wave is

travelling changes the speed changes. •When the speed changes the wavelength

and frequency change inversely and create a different pitch. tension diameter frequenc

ypitch