The Golden Ratio (φ = 1.618) is a mathematical principle from ancient Greek geometry, describing a proportion where the ratio of the whole to the larger part equals the ratio of the larger part to the smaller. Applied to room design, it spaces the three major room resonant nodes so they differ by a golden progression — preventing nodes from stacking at the same frequency and causing bass problems.

Developed by Argentine acoustician Oscar Juan Bonello in 1981, the Bonello Criterion evaluates a room's modal distribution by dividing the frequency range into 1/3 octave bands and counting the number of room modes in each band. For a room to be considered acoustically well-behaved, each successive band must contain at least as many modes as the previous one — a monotonically non-decreasing sequence. When a band contains fewer modes than the one before it, that frequency region is under-represented, causing audible bass coloration and uneven modal energy. A room that passes the Bonello Criterion has well-distributed low-frequency resonances, meaning no single frequency region dominates or goes missing from the listening experience.