UP, Ch 3 Parameters of Sound Waves

Parameters of Sound Waves

• Definition of Parameters: Features that describe sound waves.

• Seven Key Parameters:

  • Period

  • Frequency

  • Amplitude

  • Power

  • Intensity

  • Wavelength

  • Speed

• Importance of Units: Each parameter has specific units of measurement.

  • Examples of Units:

  • Age: years, seconds, minutes, decades.

  • Height: inches, feet, millimeters, miles.

• Synonyms: Some parameters may have alternate names, thus it is crucial to be familiar with various terminologies.

Source and Medium

• Source of Sound Waves:

  • Ultrasound System and Transducer: These establish certain parameter levels but some parameters can also be adjusted by the sonographer.

• Medium: The tissue through which sound travels can also affect parameters.

Parameter Adjustability

• Control of Parameters: Understanding whether a parameter can be altered by the sonographer using the ultrasound system is essential. Not all parameters can be adjusted.

• Typical Values: Familiarity with common values in clinical medicine helps in effective diagnostics.

Detailed Examination of Parameters

1. Period

• Definition: Time taken for one complete cycle of a wave.

• Units: Measured in microseconds, seconds, hours, or days.

• Typical Value in Ultrasound: $0.06$ to $0.5$ microseconds.

• Determination:

  • Controlled by the sound source only.

  • Not adjustable by the sonographer.

2. Frequency

• Definition: Number of cycles occurring in one second.

• Units: Measured in Hertz (Hz). 1 Hz = 1 cycle/second.

• Typical Values: Range from $2 ext{ MHz}$ to $15 ext{ MHz}$ (or $2,000,000 ext{ Hz}$ to $15,000,000 ext{ Hz}$).

• Determination:

  • Determined solely by the sound source.

  • Not adjustable by the sonographer.

3. Sound Classification Based on Frequency

• Infrasonic: Frequency < $20 ext{ Hz}$ (inaudible).

• Audible Sound: Frequencies between $20 ext{ Hz}$ and $2,000 ext{ Hz}$.

• Ultrasonic: Frequencies > $20,000 ext{ Hz}$ (inaudible to humans).

• Ultrasound importance: Affects penetration and image quality, which is essential in sonography.

Frequency and Period Relationship

• Inversely Related: As frequency increases, period decreases.

• Reciprocal Relationship:

  • The product of the period and frequency is one.

  • Example: If frequency is $8 ext{ Hz}$ , then period = $rac{1}{8} ext{ seconds}$.

• Clarification on Hertz: Understanding Hz as events per second; for instance, $100 ext{ Hz}$ means 100 cycles (events) per second.

Conclusion

• Understanding these parameters and their relationships is crucial for effective usage of ultrasound technology in clinical settings. Familiarization with standard values and the physical principles behind them will benefit sonographers in their practice.