Basics of Sound Quiz

Basics of Sound

• Sound is energy in the form of pressure waves, originating from mechanical actions and categorized as mechanical waves.
• Created by a vibrating source, sound causes medium molecules to oscillate back and forth.
• Requires a medium (solid, liquid, or gas) for propagation; does not travel in a vacuum.
• Recognized as a mechanical, longitudinal wave.

Historical Perspective in Ultrasound

• Medical ultrasound emerged shortly after World War II.
• Dr. Karl Theodore Dussik published the first work on transmission ultrasound for brain investigations in 1942.
• Clinical ultrasound technology was developed in Glasgow in 1956 by Ian Donald and Tom Brown, utilizing industrial flaw detection techniques.
• By the end of the 1950s, ultrasound was standard practice in Glasgow hospitals.
• Commercial ultrasound systems became available in the mid-1960s.

Acoustic Variables

• Acoustic variables represent changes within a medium due to sound propagation.
• Three primary acoustic variables include:
  • Pressure: Variations in molecules' closeness during sound wave propagation.
  • Density: Changes in mass per unit volume due to compression and rarefaction.
  • Distance: Measurement of particle motion, also called vibration or displacement.

Wave Characteristics

• Each complete wave cycle consists of two phases:
  • Compression: Molecules are pressed closely together.
  • Rarefaction: Molecules are pushed farther apart.
• Wavelength: Horizontal distance between successive crests or troughs of a wave.
• Amplitude: Maximum displacement of the wave from its mean position.
• Propagation: Direction in which the wave travels, typically indicated in diagrams.

Parameters of Sound

• Parameters represent measurable quantities and can have direct or inverse relationships.
• Key parameters of sound waves include:
  • Period
  • Frequency
  • Amplitude
  • Power
  • Intensity
  • Propagation speed
  • Wavelength

Period and Frequency

• Period (T): Time taken for one complete wave cycle, measured in microseconds (μs).
• Frequency (f): Number of cycles that occur in one second, expressed in Hertz (Hz), kilohertz (kHz), or megahertz (MHz).

Propagation Speed

• Propagation speed (c): Velocity at which a sound wave travels through a medium, measured in meters per second (m/s) or millimeters per microsecond (mm/µs).
• Sound travels fastest in solids, particularly bone, and slowest in gases, such as within the lungs.
• Average speed of sound in soft tissue is approximately 1540 m/s or 1.54 mm/µs.

Factors Influencing Propagation Speed

• Propagation speed is affected by two main properties:
  • Stiffness (elasticity): Ability of the medium to resist compression, relating to its hardness.
  • Density (inertia): Amount of mass in the medium, affecting how sound travels through it.