When we change a feeble sound to a loud sound,we increase its:

$(a)$ What is the cause of the sensation of sound due to the rolling of thunder?
$(b)$ Give the audible range of the human ear.
$(c)$ What are infrasonic and ultrasonic waves?

Give four practical uses of ultrasonic vibrations.

$(a)$ What are the basic factors on which the speed of sound in a medium depends?
$(b)$ Why are sound waves called mechanical waves?
$(c)$ How will you differentiate a high-pitch sound from a low-pitch sound with the help of a graph?

$A$ person fires a gun in front of a building $167 \ m$ away. If the speed of sound is $334 \ m \ s^{-1}$,calculate the time in which he hears an echo. (in $s$)

What is a longitudinal wave?