The coefficient of effectiveness decreases with the relative size of the larger opening.

A ___________ is produced when part of the atmosphere is compressed suddenly.

Clean air should contain less than ______ of suspended impurity per cubic metre.

For atmospheric air medium, the sound velocity at 20°C is about ____

Rock wool comes under which of the following classifications of absorbents?

The range of audible sound too painful noise varies from ____ decibel.

In summer, it is necessary to supply _______ air inside the room before it enters the room.

The speed at which the sound wave travels or passed through any medium is termed as the __________