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Ch 3-Des Sound Waved
Ultrasound Physics
| Question | Answer |
|---|---|
| ________ describe features of a sound wave. | Parameters |
| The _____ of a sound wave is the ultrasound system and transducer. | source |
| The tissue through which the sound is traveling is the _______. | medium |
| ______ is the time it takes a wave to vibrate a single cycle, or the time from the start of a cycle to the start of the next cycle. | Period |
| Period is reported in units of time such as: | seconds |
| The typical value of period is: | 0.1 to 0.5 microseconds or ms |
| Can the sonographer adjust period? | No |
| Period is determined by the ______. | source |
| ________ is the number of particular events that occurs in a specific duration of time. | Frequency |
| Frequency is reported in units of _________. | hertz |
| What is the typical value of frequency? | 2-14 MHz |
| Frequency of a sound wave is determined by the _______ _______ only. | sound source |
| Is frequency adjustable? | No |
| Period and frequency are ______ related. | inversely |
| What is the audible range? | 20Hz-20kHz |
| A frequency so high that humans cannot hear it is called ________. | ultrasound |
| What is the frequency range of ultrasound? | greater than 20 kHz |
| Sound waves with frequencies so low that humans can not hear them are called _________. | infrasound |
| What is the frequency range of infrasound? | less than 20 Hz |
| As frequency increases, period _________. | decreases |
| As frequency decreases, period _________. | increases |
| Period X Frequency= | 1 |
| What are the 3 parameters that describe the size, magnitude or strength of a sound wave? | amplitude, power and intensity |
| Amplitude is determined only by the: | sound source |
| Is amplitude adjustable? | yes |
| __________ _________ is the difference between maximum and minimum values of an acoustic variable> | Peak-to-peak amplitude |
| What is the difference between the minimum value and the average value of the acoustic variable? | amplitude |
| What is the rate of energy transfer or the rate at which work is performed? | power |
| Power has units of ______. | watts |
| What is the typical value for power? | 0.004 to 0.090 watts |
| Power is determined by ________. | source |
| Is power adjustable? | Yes |
| If amplitude increases by a factor of 3, what happens to intensity? | it increases 9-fold |
| If amplitude increases by a factor of 3, what happens to power? | it increases 9-fold |
| If a sonographer decreases the amplitude of a wave to 1/2 of it's orginal value, how has the power changed? | decresed to 1/4 of it's original value |
| What is the concentration of energy in a sound beam? | Intensity |
| What is the unit of intensity? | watts/cm2 |
| What is the typical value of intensity? | 0.01 to 300 W/cm2 |
| What is intensity determined by? | sound source |
| Is intensity adjustable? | Yes |
| When intensity increases, _______ and ________ also increase. | power,amplitude |
| _________ is the distance or length of one complete cycle. | Wavelength |
| _________ is measured in units of mm, meters, or any other unit of length. | Wavelength |
| What is the typical value of wavelength? | from 0.15 to 0.8mm |
| Wavelength is determined by: | both the source and the medium |
| Is wavelength adjustable? | No |
| As frequency increases, _______ decreases. | wavelength |
| What is the wavelength of 1 MHz sound in soft tissue? | 1.54mm (1540 m/s) |
| If you have a 10MHz transducer what is the wavelength? | 0.154mm |
| ________ wavelength sound usually produces ________ quality images with greater detail. | Shorter,higher |
| Propagation ________ is the distance that a sound wave travels through a medium in 1 second. | speed |
| ______ is measured in units of meters per second (m/s) or any distance divided by time. | speed |
| What determines speed? | medium |
| Is speed adjustable? | No |
| What is the speed of sound? | 1,540 m/s (1 mile per second) |
| What is the average speed of sound in soft tissue? | 1,540 m/s |
| What is the speed of sound in bone? | 4080 m/s |
| What is the speed of sound in air? | 330 m/s |
| _______ = frequency (Hz) x wavelength (m) | speed (m/s) |
| What are the 2 characteristics of a medium that affect the speed of sound? | stiffness and density |
| ______ describes the ability of an object to resist compression. | Stiffness |
| ______ describes the relative weight of a material. | Density |
| How are stiffness and speed related? | Directly |
| How are density and speed related? | inversely |
| When stiffness increases what happens to speed? | increases |
| When density increases what happens to speed? | decreases |
| If compressability increases what happens to speed? | decreases |
| True or False. A wave with a frequency of 15,000 MHz is ultrasonic. | True. |
| True or False. If the amplitude of a wace is increased to 3 times it's original value, the intensity is increased by 6 times. | False. Intensity is proportional to the amplitude squared. If we triple the amplitude, we increase by a factor of 9. |
| True or False. If the power of a wave if halved, the intensity is reduced to one-forth it's original value. | False. Intensity is the power of a beam divided by it's cross-sectional area. If we halve the power, we will halve the intensity. |
| True or False. Propagation speed increases as frequency increases. | False. Propagation speed is determined by the medium only. Frequency is unrelated to speed. |
| Medium 1 has a density of 9 and a stiffness of 6.Medium 2 has a density of 8 and a stiffness of 6.In which medium will sound travel slower? | Medium 1. Since both media hace the same stiffness, the medium with the greater density has the lower propagation speed. |
| _____ density and _____ stiffness create the fastest speed of sound. | low,high |
| _____ density and _____ stiffness create the slowest speed of sound. | high,low |
| If intensity remains the same while the power is doubled, what has happened to the beam area? | doubled |
| A sound beam travles a total of 10 cm in 2 seconds. What is the speed of sound? | 10 cm/2 sec= 5cm/sec |
| True or False. Propagation speed increses as frequency increases. | False |
| True or False. Propagation speed increases as frequency decreases. | False |
| True of False. Propagatin speed does not change as frequency increases. | True. Propagation speed and frequency are unrelated. |
| What is the wavelength of 3 Mhz sound in soft tissue? | 0.51mm, In soft tissue, wavelength is 1.54mm divided by the frequency in MHs. |
| The effects of sound waves on tissue in the body are called _______. | bioeffects |
| The effects of tissue on sound waves are called _______ _______ _______. | acoustic propagation properties |
| The effects of a medium on an ultrasound wave are called ________ _______ _______. | acoustic propagation properties |
Created by:
jady1999