Echo Sounding

Principle of Ultrasound waves.

- Ultrasound obeys the same law as of reflection and refractions at boundaries as sound and light waves.

- When an ultrasound wave meet a boundary, some of the wave energy is reflected and some is transmitted.

• The incident intensity I is the sum of reflected intensity IR and transmitted intensity IT

• The magnitudes of the reflected and transmitted waves depends on the:– Angle of incidence– Medium

I =IR + IT

• For any medium, a quantity known as specific acoustic impedance Z is defined.

Z=ρc

Unit: kg m-2 s-1

where,c = speed of waveρ = density

Calculating Intensity of reflected wave.

• When a wave is incident normally on a boundary, the two media having specific acoustic impedance of Z1 and Z2, the ratio IR/I is given by the expression,

• Using the ratio of IR/IO , the fraction of the intensity of the reflected waves can be determined.