Actual barrier attenuation in case of a low transmission loss
In principle, the calculation of the attenuation by a barrier assumes a high transmission loss (TL>40 dBA). If this is not the case, the effectiveness of the barrier is reduced. You can use the table below to estimate the actual attenuation, based on the calculated one (assuming TL>40 dBA) and on the actual TL of the barrier. For example, a calculated attenuation of 20 dB (for a barrier with TL>40 dBA) should be reduced to 18.8 dB for a barrier with TL=25 dBA.
Table. Estimation of the actual barrier att., based on the SLIP-calculated one and the actual barrier's TL.
| SLIP-calc. barrier att. [dB] | att. for the actual TL [dBA] |
| TL>40 (dBA) | TL=30 | TL=25 | TL=20 | TL=15 | TL=10 |
| 20 | 19.6 | 18.8 | 17.0 | 13.8 | 9.6 |
| 15 | 14.9 | 14.6 | 13.8 | 12.0 | 8.8 |
| 10 | 10.0 | 9.9 | 9.6 | 8.8 | 7.0 |
| 5 | 5.0 | 5.0 | 4.9 | 4.6 | 3.8 |
| 3 | 3.0 | 3.0 | 2.9 | 2.7 | 2.2 |
| ❑ | Anmerkung: Rule of thumb for the design of a barrier: TL must be at least 10 dB higher than the (needed) barrier attenuation. |