Question

Calculate the position of the Near field region boundary for a transducer operating at 3MHz, with
a crystal diameter of 1 cm. What is the approximate beam width at a distance of 10 cm from the
transducer surface?

Answer 1

Given,

Crystal diameter (D)= 1 cm

Transducer operating frequency (F) = 3MHz

where, V is velocity of sound in air = 343 m/s

= 0.218658 m

= 21.8658 cm

The position of the Near field region boundary for a transducer operating at 3MHz, with a crystal diameter of 1 cm is 21.8658 cm.

b) to calculate divergence angle ( from center line to spread line)

= 0.01372

= 0.786^o

Same spread will be below center line too.

Beam width cab be given as,

tan = 2 x distance / beam width

0.0137 = 2 x 0.1 / beam width

beam width = 14.5758 m

So, approximate beam width at a distance of 10 cm from the transducer surface is 14.5758 m.