Frequently Asked Questions

We can provide a large range of Acoustic and Sound Attenuating ventilators that can provide a sound reduction of anything from 26Dnew to 55Dnew whilst providing up to 33000mm2/m of Equivalent area. It is important to be able to provide an acoustical and ventilation performance in tandem.

Dnew or Rw as it is sometimes referred to is the weighted average result of a product when tested using the standard Kilohertz frequencies.

Sound waves vibrate at different rates or frequencies with either direct, when somebody directly speaks to you or reflective sound paths which are generated by sound that is reflected from walls ceilings or floors. These different frequencies are known as Hertz

Sound is measured in Decibels dB(A) and as the Human ear is very sensitive the scale is such that near silence is classed a 0 dB and if this sound was magnified by 1000 times more than near silence it would represent 30 dB.

The product is housed within a dividing wall and when testing acoustic ventilators, it is important that the product performance is tested when in the open position so that in practice the ventilator performance is known for both its sound reduction and its ventilation performance as that is what you want from a ventilator. Sound is generated from one side of the dividing wall at a controlled Hertz level and then the sound is recorded on the other side of the dividing wall known as the receiving room to measure what the sound reduction was at a given hertz level and this result is measured in dB.  The most common Hertz testing levels are 63Hz, 125Hz, 500Hz, 1000Hz, 2000Hz and 4000Hz. The measured sound results from the receiving room of each of the Hertz levels shown above are recorded and the weighted average results are then recorded to provide the product with a Dnew or Rw level of performance and the higher the Dnew or Rw level is then the better Acoustic performance the product will provide .

After any Dnew value you will have a value for C and for Ctr. C is a pink noise correction value and Ctr is a low frequency correction number for generally traffic noise and this sound correction number must always be a negative number and not zero.