State whether the following statement is true or false:
The audible range of frequencies for human beings is $20 \, Hz - 20 \, kHz$.

$A$ 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.

Two friends were playing on identical guitars whose strings were adjusted to give notes of the same pitch. Will the quality of the two notes be the same? Give a reason for your answer.

Why can we hear echoes in long galleries and big halls?

Name the waves of frequency greater than $20,000 \,Hz$. Give one use of these waves.

$(i)$ Which property of sound wave determines:
$(a)$ loudness
$(b)$ pitch?
$(ii)$ $A$ $SONAR$ station picks up a return signal after $3 \ s$. How far away is the object? (Speed of sound in water is $1440 \ m \ s^{-1}$)
$(iii)$ How can reverberations in a big hall or auditorium be reduced?