RT60n

RT60n is a normalized reverberation-time metric used in acoustics to compare how rooms will sound independent of their size or absorption characteristics. The “n” indicates that the standard RT60 value has been adjusted to a reference condition, such as a chosen reference volume and total absorption, or a standard frequency band. Because there is no universally accepted definition, implementations of RT60n vary between studies and software tools.

Calculation and interpretation: RT60 is the time required for sound to decay by 60 dB. To obtain RT60n, a normalization factor is applied to RT60 to remove or reduce the influence of room size and absorption loading. In practice, normalization often relies on the Sabine relation T60 = 0.161 V / A, and the normalization aims to map a room’s RT60 to a reference condition (for example a reference volume Vref and a reference absorption Aref). Some definitions report RT60n per octave band (125 Hz to 4 kHz) or as an overall average, depending on the measurement approach.

Applications: RT60n is used to enable direct comparisons of acoustic performance across spaces that differ in size, shape, or material composition. It can support design decisions in architectural acoustics, auditoria planning, and room validation, as well as research comparing reverberant properties under consistent reference conditions.

Limitations: The lack of a single standard means RT60n values are not universally interchangeable. Accurate normalization relies on reliable estimates of room volume, absorption, and scattering, and the chosen reference condition should be clearly documented in any reporting. See also RT60, Sabine equation, and room acoustics.