17.1 Exercise 12

A sound wave produced by an ultrasonic transducer, moving in air, is modeled with the wave equation $s \left(x , t\right) = 4.50 \text{nm} \text{cos} \left(\right. 9.15 \times 10^{4} \text{m}^{−1} x -$
$2 \pi \left(5.00 \text{MHz}\right) t \left.\right) .$ The transducer is to be used in nondestructive testing to test for fractures in steel beams. The speed of sound in the steel beam is $v = 5950 \text{m}/\text{s} .$ Find the wave function for the sound wave in the steel beam.