Porous Absorber Calculator

The Porous Absorber calculator computes absorption characteristics for materials with an open porous structure: mineral wool, fiberglass, and acoustic foam. Key input parameters are material thickness in millimeters, specific airflow resistivity (in Pa·s/m²), and the air gap behind the panel. The model accounts for the quarter-wavelength absorption maximum effect. Why it matters: porous absorbers are the most common and financially accessible acoustic treatment tool in studios and residential spaces. Yet their effectiveness depends critically on thickness and mounting method. A 50 mm panel pressed flat against a wall is virtually useless below 500 Hz. The same panel with a 50 mm air gap begins absorbing from 250 Hz. The calculator helps you find the optimal combination of thickness and gap for your target frequency range. How to read results: the absorption curve shows the coefficient from 0 to 1 across frequency. Note the "onset frequency" — the point where the coefficient exceeds 0.5. It should be below the lower bound of the problem range in your room. Common mistakes: choosing material by brand or appearance rather than acoustic parameters; mounting panels flush against the wall without a gap; using material that is too thin for bass control; confusing material density (kg/m³) with specific airflow resistivity. Next steps: compare the result with a membrane absorber for the same range, or calculate a multi-layer construction for broader bandwidth.