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

Concrete floor floating construction provides good insulation against ______ sounds.

The branch of science which deals with origin and propagation of sound is called as _______

In __________ system, the partial vacuum is created inside of the room by exhausting the vitiated inside air by fans or …

In __________ system, the use is made of doors, windows, ventilators and skylights to make the room properly ventilated.

_________ is the number of cycles made by a sounding body per unit time.

The rate of flow of air arising due to the difference in temperature of outside and inside is given by the expression __…

Hard materials used for sound insulation are good absorbers.