OWA suspended ceilings acoustic fibre metal entrance ceilings

Reverberation time is the time taken for the sound pressure level to drop by 60 dB after the generated noise has been stopped. Areas with a long reverberation time are referred to as being `live', e.g. cathedrals and churches. Those with a short reverberation time are referred to as being 'dead', e.g. offices with thick carpets and absorbent ceilings. Suspended ceilings improve the insulation value of a soffit. With an OWAcoustic ceiling this can be up to 10 dB, i.e. a reduction of half of the audible sound. Noise from flanking paths.

A reduction of 60 dB in the sound pressure level is equivalent to the reduction of acoustic energy by a factor of one million. As a rough guide the reverberation time of a room is approximately equal to the time it takes for loud clapping to become inaudible.

Sound absorption is the reduction of sound energy. The sound absorption coefficient provides the relationship between absorption and reflection of a sound. A value of 0 represents total reflection and a value of 1 represents total absorption.

Multiplying the sound absorption coefficient by 100 provides the percentage of sound energy being absorbed, e.g. a sound absorption coefficient of 0.75 stands for a sound absorption of 75% and a sound reflection of 25%. A great deal of attention is given to ensuring that the ceiling provides the maximum level of sound insulation but it should be remembered that sound will also find its way through the walls (flanking paths). Attention should therefore be given to the room as a whole when addressing the issue of sound insulation. Various services such as HVAC, plumbing, electrical and telecommunication systems can be concealed in a ceiling void. However some may create sufficiently high levels of noise to be disconcerting, as well as annoying, to the occupants below. Dependent on the type selected, an OWAcoustic panel can

In 1920 W C Sabine published an article describing the relationship between reverberation time, the volume of a room and sound absorption. Today, there are complex computer programs to calculate the acoustic behaviour of rooms. Nevertheless, in practise most people still use Sabine's equation.

It is important to remember that the equation is based on a diffused sound field, i.e. an evenly distributed sound field in a room of equal proportions and not exceeding 2000 m3 in volume. Where service elements such as light fittings, loudspeakers and grilles break into the ceiling plane, care should be taken to ensure that any gaps or holes left are stopped or at least kept to a minimum. The room to room insulation between two adjacent rooms that have a common ceiling void is described in EN 20 140-9.