Ultrasound Physics & Instrumentation - Waves

Sound is defined as:
- Mechanical energy transmitted by pressure waves in a medium.
- A mechanical disturbance that progressively propagates (travels) through a medium at a fixed speed.
- Mechanical vibrations that pass through a medium.
- A traveling disturbance that carries energy from one place to another.

Energy: The capacity to do work.
- Examples: Electric energy, Heat energy.
Mechanical Energy: A physical parameter that can be measured.
Wave: A coordinated disturbance moving through a medium at a fixed speed.
- Mechanical Waves: Transport energy (not matter) through a medium and utilize the medium's molecules.
- Waves represent a cyclical transfer of energy.
- Examples of waves include water waves, sound waves, light, x-rays, and radio signals.

Waves can be classified based on whether they require a medium to propagate.
Mechanical Waves:
- Require a medium for propagation.
- Further classified by their mode of propagation:
  - Longitudinal Waves (e.g., Sound waves).
  - Transverse Waves (e.g., Shear waves).
Electromagnetic Waves:
- Do not require a medium; can propagate in a vacuum.
Sound Waves are specifically classified as longitudinal, mechanical waves.

Sound Wave Production:
- All sources of sound involve a vibrating object (e.g., an ultrasound transducer).
- A vibrating object continually pushes and pulls adjacent molecules.
- These adjacent molecules then vibrate, leading to vibrations in other molecules.
- This creates a