Definition of Sound:
Sound is a form of mechanical energy and is transmitted by longitudinal pressure waves in a material like gas, liquid or solid.
Sound energy is said to be mechanical; as it exists in the form of physical movements of the molecules and particles in the medium. It alloys rapid back and forth displacements or vibration of molecules in the medium.
Another Point in the definition of sound is that it involves propagation through a material medium. It only exists in the media containing molecules and particles including air, water and tissue in the body.
Longitudinal Sound Waves
Sound waves that travel though tissue are longitudinal waves. It’s the form of wave motion in which the particle motion of the medium is parallel to the direction of the wave (energy) travel or propagation. Its composed of two portions.
of compression, the particles are squeezed together, resulting in increased pressure. In areas of rarefaction, the particles are drawn apart, resulting in decreased pressure. Compression and rarefaction are defined in terms of pressure because sound is transmitted
the time is takes to complete a single cycle. It is reciprocal of frequency. The unit for period is microseconds (µS). As the frequency increases (cycles/second), the period (time to complete a cycle) decreases.
Velocity of Sound
Stiffness (Resistance or Hardness) = C
Density = r
throughout the beam and variations within a plus. Intensity is not uniform across the ultrasound beam and not uniform throughout the time. The power of an ultrasound beam can remain the same while the intensity can either increases or
decrease depending upon the area size. If the ultrasound beam is measured at its smallest area, this will be the area of
cannot be measured, but movements have found that the biological ..