What do you understand by the term sound energy?

Explain how the human ear works in the transmission of sound waves to the brain.

$A$ sound wave of length $70 \ cm$ travels $840 \ m$ in $2.5 \ s$. What is the velocity and frequency of the sound?

State whether the following statement is true or false:
The wavelength of $5\, MHz$ ultrasound in a medium where the velocity is $1540\, m s^{-1}$ is $0.3\, mm$.

State three conditions necessary for sound to be heard.

$A$ hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in a tissue in which the speed of sound is $1.7 \, km \, s^{-1}$? The operating frequency of the scanner is $4.2 \, MHz$ $(1 \, MHz = 10^{6} \, Hz)$.