A man stands on the ground at a fixed distance from a siren which emits sound of fixed amplitude. The man hears the sound to be louder on a clear night than on a clear day.

Explanation

The intensity of sound at a given point is the enery per second received by a unite are perpendicular to the direction of propagation.
`I=1/2rhovomega^(2)A^(2)s`
Also intensity varies as distanc from the point source as `I prop1/r^(2)`
None of the parameters are changing incase of a clear night or a clear day.Therefore the intensity will remain the same.