Sound Waves

Mechanical Waves Mechanical Waves – waves that need a medium to transport energy and travel through EX: Sound, Water, Seismic

Acoustic Waves Acoustic Waves – also known as sound waves Vacuum – empty space where mechanical waves cannot travel

Interacting Particles In a sound wave, air particles interact with each other In a slinky wave, coils interact with each other In a stadium wave, the fans interact with each other

More dense = Faster speed Speed of Sound Medium Speed Solid Fast Liquid Gas (Air) Slow Vacuum None More dense = Faster speed

Speed of Sound As air temperature ↑, the speed of sound ↑

Pitch Pitch – how high or low a sound seems to be –generated by the frequency of the wave

Amplitude Amplitude – loudness of the sound (volume control)

How Sound is Created Sound (human voice) is created by the vibrations in the vocal cords Human Audio Frequency

Doppler Effect Doppler Effect – the change in frequency and wavelength due to the motion of the source

Doppler Effect Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle If the bug bobs in the water at a constant frequency, the wavelength will be the same for all successive waves The wave frequency is the same as the bug’s bobbing frequency

Doppler Effect Each wave crest has a shorter distance to travel so they arrive more frequently The bug maintains the same bobbing frequency as before However, an observer at B would encounter a higher frequency if the bug is moving toward the observer Each crest has to travel farther than the one ahead of it due to the bug’s motion

Faster because it’s a liquid compared to a gas Question Is the speed of sound faster or slower in water compared to its speed in air? Faster because it’s a liquid compared to a gas