Sound and Ultrasound Physics

Flashcards covering the fundamental properties of sound waves, acoustic variables, parameters, and interference patterns as used in diagnostic ultrasonography.

Sound

A mechanical wave in which particles in the medium move; the molecules vibrate back and forth from a fixed position.

Acoustic propagation properties

The effects of the medium upon the sound wave.

Biologic effects

The effects of the sound wave upon the biologic tissue through which it passes.

Acoustic variables

Pressure, density, and distance; used to distinguish sound waves from other types of waves.

Pressure

Concentration of force in an area, measured in pascals ($Pa$).

Density

Concentration of mass in a volume, measured in $kg/cm^3$.

Distance

A measure of particle motion, measured in units such as $cm$, $mm$, feet, or miles.

Acoustic parameters

Seven features used to describe a sound wave: Period, Frequency, Amplitude, Power, Intensity, Wavelength, and Propagation speed.

Transverse Waves

Waves in which particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates.

Longitudinal Waves

Waves in which particles move in the same direction that the wave propagates; sound is an example of this wave type.

In-Phase Waves

A pair of waves where peaks (maximum values) and troughs (minimum values) occur at the same time and at the same location.

Out-of-Phase Waves

A pair of waves where peaks and troughs occur at different times; they are described as being "out of step."

Interference

A phenomenon where multiple beams arrive at the same location at the same time and combine to form a single wave.

Constructive Interference

The interference of a pair of in-phase waves that results in the formation of a single wave of greater amplitude than either of its components.

Destructive Interference

The interference of a pair of out-of-phase waves that results in the formation of a single wave of lesser amplitude than at least one of its components.