Sound

Sound

If a tree falls in the forest and there is nobody around does it make a sound?

Sound

•Disturbance (energy source)

•Medium (wave travels through)

•Air•Water•Steel

Sound in (Medium) Air

Compression waves travel through air

Sound wave are called Longitudinal Waves

Sound in (Medium) Air

Sound can not travel in a vacuum

Speed of Sound

The speed of sound in dry air at 0oC is about 330 meters per second ( 330m/s )

770 miles per hour mph

Speed of Sound

Water vapors in the air increase the speed of sound slightly

Speed of Sound

Increase in temperature also increases the speed of sound

For each 0oC, the speed of sound in air increases by 0.06m/s

Example:

At normal room temperature of about 200C sound travels at about 340m/s

Loudness

Loudness is sound intensity.

The greater the disturbance (intensity) the greater the sound wave

Loudness is measured in units of Decibel (dB)

Forced Vibration

The transfer of vibration from the primary medium to secondary medium, increasing amplitude

Natural Frequency

When an object composed of an elastic material is disturbed, it vibrates at its own special set of frequency, which together forms a special sound.

We speak of an object’s natural frequency, which depends on factors such as the elasticity and shape of the object

Resonance

When the frequency of a forced vibration on an object matches theObject’s natural frequency, a dramatic increase in amplitude occurs

This phenomenon is called resonance.

Resonance means to re-sound or sound again.