Chapter 2 Physics

Mechanical Wave

particles in the medium move

What do waves carry?

energy from one place to another

Sound needs what to travel?

A medium - it cannot travel through a vacuum

Compression (Compressed)

molecules are squeezed together

Rarefaction (Rarefied)

molecules are stretched apart

What type of waves are sound waves?

Longitudinal

How do sound waves travel?

In a straight line

Acoustic Propagation Properties

Effects of the medium upon the sound wave

Biologic Effects

Effects of sound wave upon the biologic tissues it passes through

3 Acoustic Variables

Pressure, Density, Distance

Pressure

Concentration of force in an area - Pascals (Pa)

Density

Concentration of mass in a volume (kg/cm3)

Distance

Measure of particle motion (cm, mm)

What must happen to 1 of the acoustic variables for it to be considered a sound wave?

Rhythmic Oscillation

Sound waves are also known as?

Acoustic Waves

7 Acoustic Parameters

Period, Frequency, Amplitude, Power, Intensity, Wavelength, Propagation Speed

Transverse Wave

Particles vibrate in place up and down (perpendicular)

Longitudinal Wave

Particles vibrate in place left to right - all sound is longitudinal

In-Phase Waves

A pair of waves that their peaks & troughs occur at the same time and place (synchronized)

Out-of-Phase Waves

A pair of waves in which their peaks and troughs occur at different times (out of step)

Constructive Interference

In phase waves combine to form a single wave of greater amplitude

Destructive Interference

out of phase waves combine to form a single wave of lesser amplitude