# SPI Reiview

 what does an ellipse measure? area length cm, feet area cm^2, ft^2 volume cm^3, ft^3 percent is not a unit "increase by a factor of" means multiply decrease by a factor of means divide 10^9 = billion giga = G 10^6 = million mega = M 10^3 = thousand kilo = k 10^2 = hundred hecto = h 10^1 = ten deca = da 10^-1 = tenth deci = d 10^-2 = hundreth centi = c 10^-3 = thousandth milli = m 10^-6 = millionth micro = μ 10^-9 = billionth nano = n acoustic propagation properties the effects of the medium upon the sound wave biologic effect the effects of the sound wave upon the biologic tissue sound a type of wave that carries enery, not matter from place to placemust travel through a mediumis mechanical, longitudinal wavetravels in a straight line compressions are areas of increased pressure or density rarefactions are areas of decreased pressure or density three acoustic variables pressure = concentration of force w/i area force / area units= pascal (Pa)density = concentration of mass w/i volume units = kg/cm^3distance = measure of particle motion units = cm, ft, miles transverse wave particles move in a perpendicular direction (right angles or 90) to the direction of the wave sound is longitudinal wave particles move in the same direction as the wave acoustic parameters periodfequencyamplitudepowerintensityspeedwavelength period the time required to complete a single cycle (the start of a cycle to the start of the next)units = any unit of timedetermines by = sound sourcecan not be changed by sonographer frequency number of certain events that occure in a particular time durationunits = per second, 1/second = Herts (Hz)determined = sound sourcecan not be changed by sonographerfrequency affects penetration and axial resolution ultrasound a wave with a frequency exceeding 20,000Hz (20 kHz)frequency is so high that is not audible audible sound heard by man, frequencies btwn 20Hz and 20,000Hz infrasound sound with frequencies less than 20Hzfrequency is so low that is not audible frequency and period are reciprocalsfrequency (Hz) x period (sec) = 1period (sec) = 1/ frequency (Hz)frequency (Hz) = 1/period (sec)when one goes down the other goes up Three bigness parameters amplitudepowerintensity amplitude the difference btwn the average value and the maximum value of an acoustic variable. the variation of an acoustic variableunits = same as acoustic variablespressure=pascalsdensity=grams/cubic cmparticle motion=cm,inches,units of distancemay be expressed in decibels (dB)determined by sound source (initially)can be changed by sonographer power the rate that work is performed, or the rate of energy transferunits = wattsdetermined by sound source (initially)can be changed by sonographer power & amplitude power is porportional to the wave's amplitude squared ex: if amplitude is tripled, the power is increase by a factor of nine: 3 x 3 = 9 intensity the concentration of energy in a sound beam. the beam's power devided by the beam's cross-sectional area. intensity depends upon bothe the power and the cross-sectional area of the beam Authormonkies ID67978 Card SetSPI Reiview DescriptionEdelman Updated2011-02-22T04:23:21Z Show Answers