Sound Wave Period and Frequency
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Sound Wave Period and Frequency

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Questions and Answers

What is the symbol used to represent the period of a sound wave?

T

If one cycle of a sound wave takes 0.2 μs to occur, what is the frequency of the wave?

5 MHz

What is the unit of measurement for wavelength?

millimeters

Can the wavelength of a sound wave be controlled by the sonographer?

<p>No</p> Signup and view all the answers

What is the formula to calculate wavelength?

<p>λ = c ÷ f</p> Signup and view all the answers

What is the effect of shorter-wavelength sound waves on the diagnostic quality of ultrasound images?

<p>Superior spatial resolution but less penetration</p> Signup and view all the answers

What is the propagation speed of a sound wave dependent on?

<p>Medium through which it travels</p> Signup and view all the answers

What is the speed of sound wave propagation in a specific medium?

<p>Consistent regardless of frequency</p> Signup and view all the answers

What is the primary effect of a decrease in area on the intensity of an ultrasound pulse?

<p>It increases the power of the pulse</p> Signup and view all the answers

What is the term used to describe the weakening of an ultrasound pulse as it travels through a medium?

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

What is the maximum amount of variation that occurs in an acoustic variable, such as pressure, in an ultrasound wave?

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

What is the primary purpose of the dead time in a pulsed ultrasound wave?

<p>To allow for the reception of echoes</p> Signup and view all the answers

What is the term used to describe the range of frequencies emitted by a pulsed ultrasound transducer?

<p>Frequency bandwidth</p> Signup and view all the answers

What type of ultrasound diagnostic images are generated by pulsed wave transducers?

<p>Both real-time and static images</p> Signup and view all the answers

What is the primary application of continuous wave ultrasound?

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

What is a limitation of continuous wave ultrasound?

<p>It is unable to create anatomic images</p> Signup and view all the answers

What is the effect on PRF when the imaging depth is increased?

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

What is the relationship between PRP and PRF?

<p>PRP is inversely proportional to PRF</p> Signup and view all the answers

What is the typical unit of measurement for PRP?

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

What happens to the pulse-repetition period when PRF increases?

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

What is the formula to calculate pulse duration?

<p>PD = n × T</p> Signup and view all the answers

What is the effect on pulse duration if the number of cycles in a pulse is decreased?

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

What is the duty factor in terms of PRP?

<p>The fraction of the PRP that the sound is on</p> Signup and view all the answers

What is the typical range of PRP values in clinical imaging?

<p>100 microseconds to 1 millisecond</p> Signup and view all the answers

What is the primary purpose of the listening time in pulsed ultrasound?

<p>To receive echoes that form a scan line on the instrument display</p> Signup and view all the answers

What is the unit of measurement for pulse duration in the calculation of duty factor?

<p>Microsecond (µs)</p> Signup and view all the answers

What is the typical range of duty factors for Doppler ultrasound?

<p>0.5% to 5.0%</p> Signup and view all the answers

What determines the axial resolution in ultrasound imaging?

<p>Spatial pulse length</p> Signup and view all the answers

What is the formula to calculate the spatial pulse length (SPL)?

<p>SPL = wavelength × number of cycles</p> Signup and view all the answers

How does the spatial pulse length (SPL) change with increasing frequency?

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

What is the primary factor that determines the spatial pulse length (SPL)?

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

Can the sonographer adjust the duty factor during an ultrasound examination?

<p>Yes, by changing the imaging depth</p> Signup and view all the answers

What is the approximate speed of sound in fat?

<p>1450 m/sec</p> Signup and view all the answers

Which of the following best describes amplitude in relation to a sound wave?

<p>The strength or intensity of a sound wave.</p> Signup and view all the answers

What is the unit of power commonly used in diagnostic ultrasound?

<p>Milliwatt (mW)</p> Signup and view all the answers

What happens to intensity when the area over which the power is spread increases?

<p>It decreases.</p> Signup and view all the answers

What is the primary factor that determines the speed of sound in different materials?

<p>All of the above.</p> Signup and view all the answers

What is the purpose of power in ultrasound?

<p>To facilitate the displacement of particles within the medium.</p> Signup and view all the answers

What is the unit of intensity?

<p>Milliwatt per centimeter squared (mW/cm²)</p> Signup and view all the answers

What is the relationship between power and intensity?

<p>Power is the rate of energy transfer, while intensity is the rate of energy passage per unit area.</p> Signup and view all the answers

Study Notes

Sound Wave Parameters: Period

  • The period (T) is determined by the sound source and cannot be altered by the sonographer.
  • Each cycle occurs in a specific time, and the period is the time for one cycle to occur.
  • If one cycle takes 0.2 μs to occur, the frequency is 5 MHz.

Sound Wave Parameters: Wavelength

  • Wavelength (λ) is the length of a cycle in space.
  • Units for wavelength are measured in meters, millimeters, or any standard unit of length.
  • Typical values in soft tissue range from 0.1 to 0.8 mm.
  • The wavelength cannot be modified by the sonographer.
  • Wavelength is calculated as Speed divided by Frequency (λ = c / f).

Sound Wave Parameters: Propagation Speed

  • Propagation speed (c) refers to the rate at which a sound wave moves through a medium.
  • Within a specific medium, sound waves travel at a consistent speed, regardless of their frequency.
  • The speed of sound wave propagation varies across different mediums.
  • The average propagation speed of sound in tissues:
    • Air: 330 m/sec
    • Fat: 1450 m/sec
    • Water: 1480 m/sec
    • Soft tissue: 1540 m/sec
    • Bone: 4100 m/sec

Sound Wave Parameters: Amplitude

  • Amplitude is created by the number of molecules displaced by a vibration.
  • Amplitude is indicative of the strength or intensity of a sound wave.
  • Amplitude is typically measured in units of pressure, such as Mega Pascals (MPa).

Sound Wave Parameters: Power

  • Power is the rate at which work is performed or energy is transferred.
  • In ultrasound, power refers to the generation of ultrasound waves by the transducer and their propagation through tissues.
  • The standard unit of power is the Watt (W).
  • Power in diagnostic ultrasound is commonly expressed in milliwatts (mW).

Sound Wave Parameters: Intensity

  • Intensity (I) is the rate at which energy passes through a unit area.
  • Intensity is equal to the power in a wave divided by the area (A) over which the power is spread.
  • Intensity units include milliwatts per centimeter squared (mW/cm²) and watts per centimeter squared (W/cm²).

Pulsed Wave

  • A pulse has a distinct beginning and end.
  • Pulsed ultrasound comprises two main components: The Cycle (the "on" or "transmit" time) and The Dead Time (the "off" or "receive" time).
  • Pulsed transducers are designed to generate multiple, sequential, short pulses, allowing for the simultaneous use of the same crystal or group of crystals for both sound transmission and echo reception.

Pulsed Repetition Frequency (PRF)

  • Pulse Repetition Frequency (PRF) refers to the number of sound pulses generated by the transducer per second.
  • The determination of PRF is attributed to the sound source and can be adjusted by the sonographer.
  • There is an inverse relationship between imaging depth and PRF, meaning as imaging depth increases, PRF decreases.

Pulse Repetition Period (PRP)

  • Pulse-repetition period (PRP) refers to the time from the beginning of one pulse to the beginning of the next one.
  • PRP is the reciprocal of Pulse Repetition Frequency (PRF), expressed in milliseconds or any unit of time (PRP = 1 / PRF).
  • The determination of PRP is influenced by the sound source, and it can be adjusted by the operator.

Pulse Duration (PD)

  • Pulse duration (PD) is the time that it takes for one pulse to occur.
  • PD is equal to the period (the time for one cycle) times the number of cycles in the pulse (n) and is expressed in microseconds (PD = n × T).
  • Sonographic pulses are typically two or three cycles long, while Doppler pulses are typically 5 to 30 cycles long.

Duty Factor (DF)

  • The duty factor is the percentage of time that the ultrasound system transmits sound.
  • DF is the fraction of the PRP that the sound is on.
  • Typical DFs for sonography are in the range of 0.1% to 1.0%, and for Doppler ultrasound, the range is 0.5% to 5.0%.
  • The sonographer can adjust the duty factor when changing imaging depth.

Spatial Pulse Length (SPL)

  • SPL is the length of a pulse from front to back.
  • SPL is equal to the length of each cycle times the number of cycles in the pulse (SPL = n × wavelength).
  • SPL determines axial resolution.
  • Because wavelength decreases with increasing frequency, SPL decreases with increasing frequency.

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Understanding the period of a sound wave and its relation to frequency. Learn how to calculate frequency from period and vice versa.

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