The lowest axial room mode frequency equals 172 divided by the room dimension in meters

A standing wave forms when a bass wavelength fits exactly between two parallel walls, floor and ceiling, or other parallel surfaces. The first (fundamental) axial mode occurs when the dimension equals half the wavelength: f = c/(2L), where c ≈ 344 m/s. Simplified: f ≈ 172/L_meters. Subsequent modes occur at integer multiples (harmonics) of this frequency. Understanding this formula lets a mix engineer predict which frequencies will be problematic in a given room and plan acoustic treatment accordingly, or at minimum know which low-end bass judgments to trust less.

Examples

Room length 4 m → first axial mode at 172/4 = 43 Hz. Second mode at 86 Hz, third at 129 Hz, etc. A 2.42 m ceiling gives first vertical mode at 71 Hz.

Assessment

Calculate the first axial room mode for a room that is 5 meters long. State what happens to the perceived bass level at a node versus an antinode of that mode.