Vibrations Induced by Ultrasound

Sound waves are usually represented as a series of vertical lines, with intensity being related to separation between them, or as a sine wave where intensity is related to the amplitude (Figure 2).

Ultrasonic irradiation of a liquid medium gives rise to an acoustic pressure (Pa) which is added to the hydrostatic pressure (Ph) which exists in the medium. The acoustic pressure depends on time according to the following expression:

Pa = PA sin 2nft where f is the frequency of the wave ( > 16 kHz), t is the time and PA is the maximum pressure amplitude of the wave. At the point where the lines are close to each other, pressure is higher than normal (i.e. compression region), whereas at the point where the lines are furthest apart, pressure is lower than normal (i.e. rarefaction region).

The intensity of the wave can be defined as the energy transmitted per second per cm2 of fluid and can be related to PA as follows:

Figure 2 Sound motion in a liquid medium.

where c is the velocity of sound in the medium and p is the density of the medium.

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Solar Panel Basics

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