Unit 2: Sound Waves

Introduction

• Presenter: M from Sano Nerds
• Topic: Understanding Sound and Ultrasound

Basics of Sound

• Sound is a type of wave that carries energy
• *Five Key Characteristics of Sound:
  1. Sound is a wave that carries energy
  2. Sound is a mechanical wave
  3. Sound is a longitudinal wave
  4. Sound travels in a straight line
  5. Sound cannot travel through a vacuum

Sound and Ultrasound

• Ultrasound uses high-frequency waves
  • Machine sends out high-frequency wave
  • Acoustic energy in the wave is transferred into the patient
  • Energy is transferred back to the machine to create images
• Study Areas in Ultrasound:
  • Acoustic propagation properties: How the body affects the wave
  • Biological effects/Bio effects: How the energy affects biological tissue

Types of Waves

• Mechanical Waves: Require a medium to propagate
  • Examples: Sound, ropes, springs, seismic activity, and water
• Electromagnetic Waves: Do not need a medium to travel
  • Examples: Light, microwaves, X-rays, infrared rays, ultraviolet rays, and radio waves
• *Key Difference:
  • Mechanical waves need a medium
  • Electromagnetic waves can travel through a vacuum or medium
• Mechanical Waves Types:
  • Transverse Waves: Particles move perpendicular to wave direction (e.g., ocean waves)
  • Longitudinal Waves: Particles move parallel to wave direction (e.g., sound waves)

Transmission of Sound Waves

• Sound waves cause particles in the medium to undergo cyclical compressions and rarefactions
  • Compression: High density and high pressure
  • Rarefaction: Low density and low pressure
• *Sound Wave Representation:
  • Sinusoidal waves represent sound waves; peaks (compressions) and troughs (rarefactions)

Acoustic Variables

• Pressure: Measured in Pascals; force in an area
• Density: Mass per unit volume; measured in kg/cm³
• Particle Motion (Distance): Distance a particle moves as it interacts with sound energy; measured in units like cm, mm, ft, or miles

Acoustic Parameters of Sound Waves

• *Seven Acoustic Parameters:
  1. Frequency
  2. Period
  3. Wavelength
  4. Amplitude
  5. Power
  6. Intensity
  7. Propagation Speed
• These will be discussed in more detail in the next unit

Interference of Sound Waves

• Sound waves can interact through Interference
  • Constructive Interference: Occurs when two waves in phase (peaks and troughs line up) add together to make a larger wave
  • Destructive Interference: Occurs when two waves out of phase (peaks and troughs do not line up) subtract from one another making the new wave smaller
  • Special Case: If two waves of the same strength and frequency are 180 degrees out of phase, they cancel each other out completely

Summary

• Review workbook and activities for better understanding
• Complete the "nerd check" for self-assessment