On what factor does the loudness of a sound depend?

Calculate the time period of a pendulum which is vibrating with a frequency of 10 hertz.

How can you show that a sounding tabla is vibrating?

When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?

Why sound cannot travel through vacuum (or through outer space)?