Acoustic Measurement
Acoustic measurement is given in terms of decibels (dB) which increase on a logarithmic scale, i.e. it cannot be manipulated in conventional arithmetical ways. (For example, 45dB + 45dB equals 48dB, not 90dB.)
The human ear does not perceive all frequencies of sound to the same extent; to allow for this, a weighting correction is applied to dB measurements. Hence the weighting correction for doorsets is Rw. Weighted apparent sound reduction index (Rw) is a single-number index which characterises the frequency-dependent airborne sound insulation performance of building elements.
Adding/subtracting decibels
Addition –
If the levels differ by The following should be added to the higher level
0 to 1dB 3dB
2 or 3dB 2dB
4 to 9dB 1dB
10dB or over 0dB
Subtraction –
If the levels differ by The following should be subtracted from the higher level
more than 10dB 0dB
6 to 9dB 1dB
6 or 4dB 2dB
3dB 3dB
2dB 5dB (approx)
1dB 7dB (approx)
Examples –
- 34dB + 37dB = 39dB
- 41dB – 36dB = 39dB
Please do not hesitate to get in contact if you require any guidance. Doorset Technology strive to provide the best level of service possible.
