Sample Thesis Paper
Ultrasound vibrations travel in the form of a wave, similar to the way light travels. However, ultrasound requires a medium (gas, liquid or a solid) for its transmission. Ultrasonic waves are generated by piezoelectric crystal that vibrates mechanically by applying alternating current across the crystal. These vibrations take place by sequence of compressions and rarefaction within the medium. The intensity of ultrasound along the beam is influenced by constructive and destructive wave interference.
The typical shape of the acoustic waveform is divided into two zones, the near field and the far field. The near field is the region directly in front of the source where the amplitude of the acoustic waves oscillates along the axis of the source through a series of maximum and minimum amplitudes that ends at the last maximum, at distance N from the source[***]. The region lying beyond N is referred to as the far field. In the far field, the amplitude of the acoustic waves along the axis decline smoothly with small oscillations appearing in the radial direction.
Measurement of ultrasonic wave velocity in a certain medium requires prior information regarding the propagation path length, L, and the time flight, T. The velocity of sound, C, in the medium is calculated by the formula below
C = L / T (1)