Bonello Chart

The Bonello criterion evaluates how evenly room modes are distributed across third-octave bands. The method was proposed by Argentine acoustician Oscar Bonello in 1981 and remains widely used as a quick indicator of a room's acoustic proportional quality. The rule states that the number of modes in each successive third-octave band must not decrease from the previous band, and no band should contain coincident (degenerate) modes at the same frequency. Why it matters: even when room proportions fall within the Bolt Area, the modal distribution across frequency can still be uneven. The Bonello criterion specifically reveals problematic bands where modes are too sparse (causing a dip in frequency response) or too heavily concentrated (reinforcing boom). This analysis is especially useful during the design phase when room dimensions can still be adjusted on paper. How to read results: on the chart, each third-octave band is represented by a bar. A monotonically increasing graph indicates good distribution. Dips point to problematic ranges. Red markers flag bands with degenerate modes. Common mistakes: blindly trusting the criterion without considering other factors — Bonello evaluates only the count of modes, not their actual energy; dismissing the result when the graph "almost" increases — even a single violation of monotonicity can be audible. Next steps: if the criterion fails, try varying the room dimensions and recalculate. Open the Room Profile and Room Modes calculator for the full picture.