A student is testing a loudspeaker connected to a signal generator. An observer is listening to the tone produced.

Initially, the observer stands at a certain distance. The observer then moves to a new position closer to the loudspeaker.

(i) State what, if anything, happens to:

1. the pitch of the sound heard.
2. the loudness of the sound heard.

(ii) What adjustment, if any, should be made to the two controls of the signal generator so that the sound heard at the new closer position is the same as it was at the original position?

• frequency control
• amplitude control

A boy stands at a distance from a tall, vertical concrete wall of a gymnasium. He claps his hands loudly once. After a brief delay, he hears the sound of the clap again.

(i) Explain why the sound returned to him. (ii) Explain why there was a short time delay before the boy heard this second sound.