Sound Waves and Interference Quiz
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Questions and Answers

What occurs when waves combine to form a wave larger than the original waves?

  • Diffraction
  • Out-of-phase interference
  • Constructive interference (correct)
  • Destructive interference

    • Destructive interference can lead to complete cancellation of the wave if the waves have equal amplitude.

    True

    Define frequency in the context of sound waves.

    The number of events that occur in a specific duration of time; cycles per second.

    The time from the start of one cycle to the start of the next cycle is known as the ______.

    <p>period</p> Signup and view all the answers

    Match the following acoustic parameters with their descriptions:

    <p>Period = Time from start of one cycle to another Frequency = Number of cycles per second Amplitude = Maximum displacement of the wave Wavelength = Distance between consecutive peaks of a wave</p> Signup and view all the answers

    What is the frequency range for ultrasound typically?

    <p>2 MHz-15 MHz</p> Signup and view all the answers

    Out-of-phase waves occur when peaks and troughs align at the same time.

    <p>False</p> Signup and view all the answers

    What happens to sound waves during interference?

    <p>They lose their individual characteristics and combine to form a new wave.</p> Signup and view all the answers

    What is the typical range for Pulse Repetition Period (PRP)?

    <p>100 µs - 1 ms</p> Signup and view all the answers

    Pulse Repetition Frequency (PRF) refers to the number of pulses transmitted per second.

    <p>True</p> Signup and view all the answers

    What happens to the Pulse Repetition Period when the imaging depth is increased?

    <p>Pulse Repetition Period increases.</p> Signup and view all the answers

    What is the relationship between wavelength and frequency?

    <p>They are inversely related</p> Signup and view all the answers

    The typical value for Pulse Repetition Frequency is between __ and __ Hz.

    <p>1,000; 10,000</p> Signup and view all the answers

    Higher frequencies result in longer wavelengths.

    <p>False</p> Signup and view all the answers

    Match each term with its correct description:

    <p>On-Time = Duration when the ultrasound is actively pulsing Off-Time = Duration when the ultrasound system is listening Pulse Repetition Period = Total time from one pulse to the next Pulse Repetition Frequency = Number of pulses transmitted per second</p> Signup and view all the answers

    What is the relationship between period and frequency?

    <p>They are reciprocally related.</p> Signup and view all the answers

    Which component can the sonographer adjust to change the Off-Time?

    <p>Imaging depth</p> Signup and view all the answers

    What is the speed of sound in soft tissue?

    <p>1.54 mm/µs</p> Signup and view all the answers

    The reciprocal of a period of 1 second results in a frequency of 1 Hz.

    <p>True</p> Signup and view all the answers

    A sound wave with a frequency of 5 MHz has a wavelength of ______ mm.

    <p>0.308</p> Signup and view all the answers

    Shallow imaging results in a longer Pulse Repetition Period (PRP).

    <p>False</p> Signup and view all the answers

    What is the equation relating period and frequency?

    <p>Period x Frequency = 1</p> Signup and view all the answers

    What is the typical value range for Pulse Repetition Period (PRP) in milliseconds?

    <p>0.1 to 1</p> Signup and view all the answers

    Match the transducers with their respective wavelengths:

    <p>GE Curved Transducer = 0.308 mm GE TV Transducer = 0.171 mm</p> Signup and view all the answers

    The typical unit of power in acoustic measurements is _____

    <p>Watts</p> Signup and view all the answers

    Which statement about sound wave penetration is correct?

    <p>Longer wavelengths provide less penetration.</p> Signup and view all the answers

    What does peak-to-peak amplitude measure?

    <p>Difference between maximum and minimum values</p> Signup and view all the answers

    Propagation speed refers to how quickly a sound wave travels through a medium.

    <p>True</p> Signup and view all the answers

    Amplitude is adjustable by the sound source.

    <p>True</p> Signup and view all the answers

    Wavelength (mm) can be calculated using the formula: Wavelength = ______ / Frequency (MHz).

    <p>1.54</p> Signup and view all the answers

    What is the peak-to-peak amplitude if the maximum value is 2 MPa and the minimum value is -2 MPa?

    <p>4 MPa</p> Signup and view all the answers

    What is the speed of sound in soft tissue expressed in mm/µs?

    <p>1.54 mm/µs</p> Signup and view all the answers

    Sound travels faster in solids than in liquids.

    <p>True</p> Signup and view all the answers

    What two characteristics of a medium determine the speed of sound?

    <p>Stiffness and Density</p> Signup and view all the answers

    The speed of sound in soft tissue is ___ km/s.

    <p>1.54</p> Signup and view all the answers

    Match the following materials with their corresponding speed of sound:

    <p>Air = Slowest Liquids = Medium speed Soft Tissue = Faster than liquids Solids = Fastest</p> Signup and view all the answers

    What is the formula to calculate the speed of sound?

    <p>Speed (m/s) = Frequency (Hz) x Wavelength (m)</p> Signup and view all the answers

    Density is defined as the ability of an object to resist compression.

    <p>False</p> Signup and view all the answers

    What happens to the pulse repetition frequency (PRF) when the imaging depth increases?

    <p>PRF decreases</p> Signup and view all the answers

    The pulse repetition period (PRP) and pulse repetition frequency (PRF) are directly related.

    <p>False</p> Signup and view all the answers

    What is the typical duty factor range for pulsed wave ultrasound?

    <p>0.2% to 0.5%</p> Signup and view all the answers

    The formula for calculating the duty factor is ___ / PRP.

    <p>Pulse Duration</p> Signup and view all the answers

    Match the imaging type with its appropriate characteristics:

    <p>Shallow Imaging = Less listening time, Higher PRF Deep Imaging = More listening time, Lower PRF</p> Signup and view all the answers

    What is the maximum duty factor for continuous wave ultrasound?

    <p>100%</p> Signup and view all the answers

    Pulsed wave ultrasound has a duty factor greater than 1.

    <p>False</p> Signup and view all the answers

    Define the duty factor in ultrasound imaging.

    <p>The percentage or fraction of time that the system transmits a pulse.</p> Signup and view all the answers

    Study Notes

    Introduction to Ultrasound Physics

    • This module introduces the fundamental physics of ultrasound.
    • Stars are used to highlight information likely to appear on the SPI board exam.
    • Sound is a mechanical wave requiring a medium to travel.
    • Sound waves cannot travel through a vacuum.

    Types of Waves

    • Waves, including heat, sound, magnetic, and light, carry energy from point A to point B.
    • Sound waves are mechanical waves—they need a medium to travel.

    Sound Waves

    • Sound waves are mechanical waves requiring a medium, like air or tissue, to transfer energy.
    • They cannot travel in a vacuum.
    • Medium affects wave propagation properties and vice versa.
    • Medium also has biologic effects.

    Acoustic Variables

    • Sound waves result from oscillations in acoustic variables (pressure, density, distance).
    • Pressure is the concentration of force in an area, measured in Pascals (Pa).
    • Density is the concentration of mass in a volume, measured in kg/cm³.
    • Distance measures the particle's motion, in cm or mm.

    Transverse vs. Longitudinal Waves

    • Transverse waves—particle movement is perpendicular to wave propagation (think ripples).
    • Longitudinal waves—particle movement is parallel to wave propagation (sound waves).
    • Sound waves are longitudinal.

    In-Phase and Out-of-Phase Waves and Interference

    • In-phase waves have peaks and troughs at the same location and time.
    • Out-of-phase waves have peaks and troughs at different locations and/or times.
    • Interference occurs when multiple sound waves travel at the same location simultaneously.

    Interference

    • Constructive interference—in-phase waves combine to produce a larger wave.
    • Destructive interference—out-of-phase waves combine, potentially eliminating the wave entirely if amplitudes are equal.

    Acoustic Parameters

    • Parameters describing a sound wave's characteristics include period, frequency, amplitude, power, intensity, wavelength, and propagation speed.
    • These parameters are influenced by transducer and medium properties.

    Period

    • Period is the time taken for one complete cycle of a wave.
    • Units are microseconds (µs).
    • Period is determined by the sound source.
    • Period is not adjustable, whereas frequency is.
    • Period and frequency are reciprocals of each other thus, their multiplication gives 1.

    Frequency

    • Frequency is the number of cycles per second.
    • Units are Hertz (Hz), or cycles per second (cps).
    • Frequency is determined by the sound source.
    • Typical ultrasound frequency values range from 2 MHz to 15 MHz.
    • Frequency and wavelength are inversely related.

    Period and Frequency

    • Period and frequency are reciprocally related (inverse).
    • Their product equals 1.
    • Formula: Period (µs) x Frequency (MHz)= 1.

    Amplitude

    • Amplitude is the difference between maximum and baseline values of a wave; it's a measure of “bigness.”
    • Peak-to-peak amplitude is twice the regular amplitude.
    • Units depend on the acoustic variable being measured.
    • Amplitude is adjustable, controlled by the sound source.

    Power

    • Power is the rate of energy transfer.
    • Units are Watts (W).
    • Power is determined by the sound source and is adjustable.
    • Power is directly proportional to amplitude squared (formula: Power=Amplitude²).

    Intensity

    • Intensity is energy concentration in a sound beam.
    • Units are Watts per square centimeter (W/cm²).
    • Intensity is determined by source and medium.
    • Intensity is adjustable and is proportional to amplitude squared.
    • Formula: Intensity (W/cm²) = Power (W) / Area (cm²).

    Wavelength

    • Wavelength is the length of one complete cycle of a wave.
    • Units are millimeters (mm), centimeters (cm), etc.
    • Wavelength is determined by both the sound source and the medium.
    • The relationship between wavelength and frequency is inversely related.
    • Formula to calculate wavelength is: Wavelength (mm) = Speed (mm/μs) / Frequency (MHz).

    Propagation Speed

    • Propagation speed is the rate at which a sound wave travels through a medium.
    • Units are meters per second (m/s), millimeters per microsecond (mm/μs), etc.
    • Propagation speed is determined by the medium (tissue, fluid, etc.) and is not adjustable.
    • The speed of sound in soft tissue is 1.540 m/s.

    Pulsed Sound

    • Pulsed sound is a collection of ultrasound cycles traveling together.
    • It has "on" (transmitting) and "off" (receiving) time components.

    Pulsed Wave Parameters

    • Pulsed wave parameters include pulse duration, pulse repetition period, pulse repetition frequency, duty factor, and spatial pulse length.
    • These characteristics determine how ultrasound pulses are transmitted and received.

    Pulse Duration

    • Pulse duration is the time from the start of a pulse to the end.
    • Units are microseconds (μs).
    • Pulse duration is determined by frequency and number of cycles in the pulse.
    • Formula to calculate pulse durations is: Pulse Duration (μs) = # cycles in the pulse x period (μs) or Pulse Duration(µs)= #cycles/Frequency(MHz).

    Spatial Pulse Length

    • Spatial pulse length is the distance from the start of a pulse to the finish.
    • The units are normally in millimeters (mm).
    • Spatial pulse length is determined by the number of cycles and wavelength.
    • SPL increases with increasing number of cycles in the pulse and increasing wavelength.

    Pulse Repetition Period (PRP)

    • The time from the start of one pulse to the start of the next pulse.
    • This refers to the entire pulse cycle, including transmitting and receiving parts.
    • When imaging deeper structures, the amount of time taken to do “listening" (receiving) is increased meaning the PRP is increased, and PRF decreased.

    Pulse Repetition Frequency (PRF)

    • The number of pulses transmitted into a medium each second.
    • Units are in Hertz (Hz).
    • PRF is inversely related to PRP.
    • Changing the pulse depth changes the PRF (and vice versa).
    • Formula: PRF x PRP = 1.

    Duty Factor

    • Duty factor is the percentage of the time during which the system transmits a pulse.
    • Duty factor (%) = Pulse Duration/PRP.
    • Typical values are about 0.2%–0.5%.

    Ultrasound Imaging

    • Shallow imaging means shorter PRP, and higher PRF. Deeper imaging means longer PRP and lower PRF.

    Stiffness and Density

    • Stiffness and density affect sound wave speed.
    • Stiffness and speed are directly proportional; denser materials and stiffer materials mean faster speed.
    • Density and speed are inversely proportional.
    • Denser materials mean slower speeds.

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    Related Documents

    Ultrasound Physics Module One Lecture PDF

    Description

    Test your knowledge on the principles of sound waves and interference. This quiz covers topics such as wave combination, frequency, and pulse repetition, helping you understand complex acoustic parameters. Perfect for students studying acoustics or related fields.

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