definitions Flashcards
a type of wave that carries energy , not matter from place to place
Sound
the effects of the medium upon the sound wave
acoustic propagation properties
the effects of the sound wave upon the biologic tissues
biological effects
acoustic variables
Pressure, density, distance
concentration of force within an area, Force/area
Units= Pascals (Pa)
Pressure
concentration of mass within a volume
Units= Kg/cm^3
Density
measure of particles in motion
Units=cm, feet, miles
Distance
particles move in a perpendicular direction (right angle) to the direction of the sound wave
Transverse waves
particles move in the same direction as the wave
Longitudinal wave
regions of higher density and pressure
compressions
regions of lower density and pressure
rarefractions
inform us of which waves are sound waves
acoustic variables
describe the features of a particular sound wave
acoustic parameters
the time required to complete a single cycle
can also be described as the time from the start of a cycle to the start of the next cycle
period
number of certain events that occur in a particular time duration
Frequency
waves with frequencies exceeding 20,000Hz (20KHz)
This frequency is so high that the sound is not audible
Ultrasound
infrasound
sound with frequencies less than 20Hz
audible sound
heard by man, frequencies between 20Hz and 20,000Hz
the difference between the average value and the maximum value of an acoustic variable. The variation of an acoustic variable
amplitude
the concentration of energy in a sound beam
the beams power divided by the beam’s cross-sectional area
Intensity
the rate that work is performed, or the rate of energy transfer
power
the length or distance of a single cycle
wavelength
the rate that sound travels through a medium.
Also called velocity and speed
Propagation speed
opposites of stiffness
compressibility and elasticity
same as stiffness
Bulk modulus
a collection of cycles that travel together
a pulse
the time from the start of a pulse to the end of that pulse
the actual time that the pulse is on
Pulse duration
the length or distance that an entire pulse occupies in space
The distance from the start to the end of one pulse
Spatial pulse length
the time from the start of one pulse to the start of the next pulse
It includes one pulse duration and one “listening time”
Pulse repetition period
the number of pulses created by the system in one second
Pulse repetition frequency
the percentage or fraction of time that the system transmits sound
Duty factor
the concentration of the power in a beam
intensity
a logarithmic scale
a relative scale
a comparison, therefore, two intensities are needed to calculate decibels
Decibels
the decrease in intensity, power and amplitude of a sound wave as it travels
This is unrelated to speed
attenuation
the amount of attenuation per centimeter
*a way to report attenuation without dealing with distance
attenuation coefficient
transmission with a bend
a change in direction as sound transmits from one medium to another
refraction
any device that converts one form of energy into another
transducer
when PZT is heated above this temperature (approximately 360C degrees or 680F degrees), it loses its piezoelectric properties, ( the PZT is depolarized)
Curie temperature / Currie point
the complete destruction of all living microorganisms by means of exposure to heat, chemical
sterilization
the application of a chemical agent to reduce or eliminate infectious organisms on an object, such as a transducer
disinfection
the piezoelectric crystal, also called the ceramic, PZT, or crystal
1/2 wavelength thick
Active element
the range of frequencies
bandwidth
a unitless number representing the extent of damping
Quality factor
the location where the beam reaches its minimum diameter
Focus or focal point
the distance from the transducer face to the focus. also called focal length or near zone length
focal depth
the region or zone in between the transducer and the focus
*sound beams converge here
Near zone (Fresnel zone)
the region or zone deeper than the focus, beyond the near field
*sound beams diverge here
Far zone (Fraunhofer zone)