(a) State the three characteristics of sound and the factor on which each of them depends.

(b) Explain resonance as applied to sound.

(c) What role does echo play in the construction of a concert hall?

(d) The surface of an ear drum (assumed circular) has a radius 2.1 mm. It resonates with an amplitude of 0.8 x 10\(^{-7}\) in as a result of impulses received from an external body vibrating at 2400 Hz. If the resulting pressure change on the ear drum is 3.6 x 10\(^{-5}\) NM\(^{-2}\), calculate the:

(i) period of oscillation;

(ii) velocity;

(iii) acceleration;

(iv) force. [\(\pi\) = 3.14 ].