Broadband Noise

Noise where the energy of the noise covers a wide range of the audible frequency.


Equivalent Sound Level: the Sound Pressure Level in decibels, dB, equivalent to the total amount of Sound Energy over a period of time.


Also known as standing waves or Eigentones. These are resonant frequencies that coincide with the dimensions of a room and are usually evident at low frequencies. Parallel walls and rooms that have two or three similar dimensions of width, breadth and height can cause modes to resonate. Treatment in small rooms can be problematic due to lack of space.

Noise Rating (NR)

NR curves, or Noise Rating curves, are a method of assessing the noise levels and thus suitability of indoor environments. Noise Ratings are measured by measuring the noise in an unoccupied room with the services, if any, operating at full demand. The noise measured will include noise from services as well as noise from outside of the room in adjacent spaces or the outdoor environment.

Reverberation Time

Often quoted as RT60 or T60, this is the time in seconds that it takes for a sound pressure level to fall by 60dB after the sound has stopped. Reverberation time can be both predicted and measured but both of these are often inaccurate when used with small rooms.


Sound Pressure Level Level: logarithmic measure of the RMS sound pressure of a sound relative to a reference value of 2.0 x 10 -5 ( or 0.00002) which is the threshold of hearing. Measured in decibels (dB).