If the amplitude of a wave is doubled, what will be the effect on its loudness?

Sound made in front of a tall building $18 \, m$ away is repeated. Name the phenomenon and briefly explain it.

The bells of a temple are made of large size. It is for

What is Galton's whistle? To what use can it be put?

What do you understand by the term echo?

$A$ sound wave with frequency higher than $20 \,kHz$ is not audible for human ear. Answer the following in respect of this statement:
$(i)$ What is the term used for such a sound?
$(ii)$ Name two organisms producing sound in this range.
$(iii)$ Write an application of such a wave.