Combined Acoustic Rating (Rw) for Glass + Frame
Glass + Frame Combined Rw — Sample Report
This page shows how to combine the acoustic performance of a glass + frame assembly and how to report it according to ISO. The calculation follows ISO 12354-3 (area-weighted energy summation) and the reporting follows ISO 717-1 (Rw, C, Ctr).
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Method & Standards [ ISO 12354-3 & ISO 717-1 ]
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ISO 12354-3: For façades composed of multiple parts (glass,
frame, joints), the combined transmission is computed with
area-weighted energy summation:
R = 10·log₁₀( Stotal / Σ Si·10^(−Ri/10) ). - ISO 717-1: From 1/3-octave band data you obtain the single-number Rw and the spectrum adaptation terms C, Ctr. Reporting format: Rw(C;Ctr).
When to use C vs Ctr? Use Rw + C for speech/office (mid-high frequencies), and Rw + Ctr for traffic/urban noise (low-frequency content). C/Ctr are not used in the combination step; they are used to interpret the combined result against the noise source.
Glass + Frame — Combined Rw [ Combined Reduction Index ]
Inputs
Results
How the Calculator Works (ISO 12354-3 & ISO 717-1)
This tool implements the energy summation principle in ISO 12354-3:2017 to combine multiple façade parts (glass, frame, joints). The final presentation follows ISO 717-1 (Rw and, where band data exist, C and Ctr).
1) Contribution of each element (ISO 12354-3 §4.2)
For “other elements” (glass, frame, panels) the sound power ratio is:
$$\tau_{e,i}=\frac{S_i}{S}\,10^{-R_i/10}\qquad\text{(Eq. 15, §4.2.2)}$$For “small elements” (vents, grilles):
$$\tau_{e,k}=\frac{A_0}{S}\,10^{-D_{n,e,k}/10},\quad A_0=10\,\text{m}^2\qquad\text{(Eq. 14, §4.2.1)}$$2) Total transmission and single-band R (ISO 12354-3 §4.1)
Sum all contributions and obtain R per band:
$$\tau_e=\sum_i \tau_{e,i}+\sum_k \tau_{e,k}\quad\Rightarrow\quad R(f)=-10\log_{10}\!\big(\tau_e\big)\qquad\text{(Eq. 1, §4.1)}$$3) Practical form for glass + frame (no small elements)
Combining the above gives the widely used expression:
$$\boxed{\,R(f)=10\log_{10}\!\left(\frac{S}{\sum_i S_i\,10^{-R_i(f)/10}}\right)}$$Here \(S=\sum_i S_i\). If only single-number data exist, use each element’s Rw as an approximation.
Reporting & adaptation (ISO 717-1)
From the combined spectrum, compute Rw and, where 1/3-octave data are available, the spectrum adaptation terms C and Ctr. These do not enter the combination step; they are used to interpret the result for speech (Rw + C) or traffic noise (Rw + Ctr).
References: ISO 12354-3:2017 — §4.1 (Eq. 1), §4.2.1 (Eq. 14), §4.2.2 (Eq. 15). ISO 717-1 — single-number quantities and spectrum adaptation terms.