Why do astronauts talk to each other through radio telephones?

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.

What do you understand by the term infrasonic vibrations?

$(a)$ What is reverberation? Write two ways of reducing reverberation.
$(b)$ Distinguish between tone and note.
$(c)$ With the help of a simple diagram,explain how defects in a metal block can be detected using ultrasound.

What is the audible range for human beings?

Write true or false for the following statement: Sound produced by a sounding body of frequency $300 \text{ Hz}$ covers $34 \text{ m}$ in the time the sounding body produces $30$ vibrations.