Modo axial de sala

Axial room mode

A room mode is an eigenfrequency that builds up whenever a sound wavelength lines up with one of the room's dimensions. For axial modes the formula is f = n · c / (2 · L), with c ≈ 343 m/s (speed of sound at 20 °C) and L the room length in metres. Take a 5 m room: its first-order axial mode lands at 34.3 Hz, with harmonics following at 68.6, 103, 137 Hz. Every pair of parallel walls produces its own series like this. The trouble is that small rooms pile up low-frequency resonances that boom and bury detail. Corners are where pressure peaks, so that's where bass traps go to soak up the energy. To check whether those modes spread evenly across the spectrum, acousticians lean on the Bonello criterion.

Applications

Designing home theatres, mixing rooms and mastering suites. Picking balanced room ratios such as Sepmeyer, Louden or Bolt. Running a Bonello analysis before anything gets built. Working out speaker and subwoofer placement so you don't end up parked on a null. And choosing where to put bass traps and tube traps at the pressure maxima.

FAQ

What about tangential and oblique modes? They're real, but usually 3–6 dB quieter than the axial ones, so it's the axial modes that cause most of the trouble you actually hear.

Why is my room boomy at 80 Hz? Most likely a wall pair has a mode sitting near that frequency. Try moving the listening position, shifting the sub, or dropping a bass trap into the corner.

Do square rooms sound bad? They tend to. Equal dimensions stack several modes onto the same frequency, which gives you huge peaks and deep nulls. Steer clear of 1:1:1 and 1:2:4 ratios.