The formation of echoes can take place when the reflecting surfaces are located at a distance greater than ______

The rate of ventilation depends on both the wind effect and the stack effect.

Which of the following is not a property of good acoustic materials?

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

______________ is a measure of quantity of sound energy.

Calculate the transmission loss given the sound levels measured on either side of the wall is 60 dB and 40 dB.

For comfortable working, the _______ content should be limited to about 0.6% by volume.

________________ are made of sheet metal of suitable size and shape to convey the conditioned air.