Sound WavesSound Waves

You Have to Hear This!!!!You Have to Hear This!!!!

Producing a Sound WaveProducing a Sound Wave

Like all waves, sound waves are produced by a vibration.

A tuning fork vibrates to produce a sound.A guitar string vibrates to produce a sound.Your vocal cords vibrate to produce a sound.A tree that falls in the woods causes a vibration and produces a sound– even if no one is around to hear it!!!!!!!

Properties of Sound Properties of Sound WavesWaves

Sound Waves are Longitudinal Waves.

As the fork moves forward and back it alternately compresses and then

decompresses the air (or whatever medium it is traveling through).

From above the source it looks more like this:

Properties of Sound Properties of Sound WavesWaves

Sound Waves are Mechanical Waves

This means they MUST have a medium (matter) to travel.

This means sound waves CANNOT travel through empty space ( a

vacuum).

Properties of Sound Properties of Sound WavesWaves

All sound travels at the same speed in the same medium.

This speed is called the speed of sound.

The speed of sound in air is : 343 m/s (767 mph)The speed of sound in water: 1433 m/s (3206

mph)The speed of sound in concrete: 3400 m/s (7606

mph)The speed of sound in steel: 6100 m/s (13645

mph)

Properties of Sound Properties of Sound WavesWaves

The speed of sound is also affected by temperature.

Basically, the higher the temperature the faster sound travels.

As an equation this looks like this:

vsound = 331 + 0.6Tc

The Doppler EffectThe Doppler Effect

Whenever a source of sound is moving, the pitch you hear depends on whether the

sound source is moving towards you or away from you.