Lecture Notes: Sound Waves

Introduction

• Presented by Sano Nerds
• Focus: Understanding sound waves, specifically ultrasound.

Key Characteristics of Sound Waves

1. Wave Type: Carries energy
2. Mechanical Wave: Requires a medium to travel
3. Longitudinal Wave: Particles move parallel to wave direction
4. Straight Line Travel: Can only travel linearly
5. Cannot Travel Through Vacuum: Requires a medium

Energy Transfer and Ultrasound

• Waves transfer energy from one location to another.
• Ultrasound: High-frequency waves sent from the machine into the body; energy reflects back to create images.
• Focus on acoustic propagation properties and bioeffects.

Types of Waves

• Mechanical Waves: Require a medium (e.g., sound, ropes, springs, seismic activity, water)
• Electromagnetic Waves: Do not require a medium (e.g., light, microwaves, x-rays)

Mechanical Waves

• Must have a medium
• Transverse Waves: Particles move perpendicular (e.g., ocean waves)
• Longitudinal Waves: Particles move parallel (e.g., sound waves)

Sound Waves

• Mechanical Longitudinal Waves: Require medium
• Compression and Rarefaction:
  • Compression: High density and pressure
  • Rarefaction: Low density and pressure
• Acoustic Variables: Pressure, density, and particle motion

Identifying Sound Waves

• Cyclical change in acoustic variables required
• Represented by sinusoidal waves

Acoustic Parameters (To be discussed in next unit)

• Frequency
• Period
• Wavelength
• Amplitude
• Power
• Intensity
• Propagation speed

Wave Interference

• Constructive Interference:
  • In-phase waves add together
  • Example: Wave A + Wave B = Larger Wave C
• Destructive Interference:
  • Out-of-phase waves subtract
  • Special case: 180° out-of-phase waves cancel each other completely

Conclusion

• Review workbook activities and conduct the nerd check.

• Reminder: Constructive interference amplifies wave, while destructive interference can diminish or nullify waves.