Strutt|Mechanical Services|Duct Breakout|Duct Breakin inserts the sound power level of sound transmitted into a duct into the active row of the worksheet.
The sound power level associated with sound transmitted into a duct through the duct walls from the space outside the duct is given by:
`L_(W,"in") = L_(W,out) + TL - 3`
`L_(W,"in")` is the sound power level of sound transmitted into the duct and then transmitted upstream or downstream of point of entry, dB
`L_(W,out)` is the sound power level of sound incident on outside of duct walls, dB. Strutt calculates this from the incident reverberant sound level `L_(p,rev)` as:
`S` is the exposed surface area of the duct (mē)
`TL` is the duct break-in transmission loss, dB (this can be input manually or via Duct TL function).
Note: TL values must be negative for formula to calculate correctly.