Giga & Nano

(G & n)

Billions & Billionths

mega & micro

(M &    )

millions & millionths

kilo & milli

(k & m)

thousands & thousandths

hecto & centi

(h & c)

hundreds & hundreths

deca & deci

(da & d)

tens & tenths

Sounds travels in a _______ line.

Straight

Sound waves are ________ waves.

Longitudinal

Areas of compression on a sound

wave are:

Squeezed Together

A rarefied area of a sound wave is:

Stretched Apart

Acoustic Variables

Pressure (Pascals, Pa)

Density (kg/cm )

Distance (cm, mm)

Pressure

Concentration of force in an area

Units: Pascals (Pa)

Density

Concentration of mass in a volume

Units: kg/cm

Distance

Measure of a particle motion

Units: cm, feet, mile...

What is an Acoustic Parameter?

A characteristic that describes

a sound wave

What are the 7 Acoustic Parameters?

Period

Frequency

Ampitude

Power

Intensity

Wavelength

Propagation Speed

Transverse Wave

Particles move in a direction that is perpendicular to the direction the wave propagates.

Longitudinal Wave

Particles move in the same direction that

the wave propagates

Sound is a Longitudinal Wave

Out-of-Phase Waves

When two waves peaks occur at different times, resulting in destructive interference.

In-Phase Waves

When a pair of waves peaks occur at the same

time and location, resulting in Constructive Intereference

Constructive Interference

The interference of a pair of in-phase waves that results in a single wave of greater amplitude.

Destructive Interference

The interference of a pair of out-of-phase waves that results in a single wave of lesser amplitude.

Period

 The time it takes a wave to complete one cycle.

Units: Time (microseconds, s..)

Typical Values: .06 to .5 microseconds (   )

Determined By: Source

Adjustable: NO

Frequency

The number of cycles that occur in 1 second.

Units: Hz (per second)

Typical Values: 2 MHz to 15 MHz (Imaging)

Determined by: Source

Adjustabe: NO

Infrasound

Less than 20 Hz

Audible Sound

Between 20 Hz and 20 kHz

(20,000 Hz)

Ultrasound

Greater than 20 kHz

*Cannot image under 2 MHz (2 million Hz)*

Period and Frequency are ______ related.

Inversely

As FQ increases, Period decreases.

As FQ decreases, Period increases

Preiod and Frequency are _______.

Reciporicals

Period x Frequency = 1

What is the meaing of a sound wave with a frequency of 100 Hz?

A frequency of 100 Hz means there are 100 cycles per second.

Three "Bigness" Parameters

Amplitude

Power

Intensity

Amplitude

The "bigness" of a wave. The difference between the max value and the average value of an acousitc variable.

Units: Pa, decibels (dB), density (g/cm )

Typical Values: 1 million Pascals (1MPa) to 3Mpa.

Determined by: Source

Adjustable: Yes

Power

The rate at which work is performed.

Units: Watts

Typical Values: .004 watts to .090 watts

(4 to 90 milliwatts)

Determined by: Sound Source

Adjustable: Yes

How are Power and Amplitude related?

Power is proportional to the

amplitude squared.

Intensity

Concentration of energy in a sound beam.

Beams Power / beams cross sectional area

Units: W/cm

Typical Values: .01 to 300 W/cm

Determined by: Source

Adjustable: Yes