Reference level difference

Professional Definition

A magnitude determined according to a formula that takes into account the difference in sound pressure levels adjusted for reverberation time in the receiving room.

This refers to a parameter designated as DnT. It is the difference in sound pressure levels between the transmitting room and the receiving room, increased by a correction term depending on the reverberation time (T) measured in the receiving room relative to the reference time (T0, usually 0.5 seconds). The formula takes the form: DnT = L1 - L2 + 10 log(T/T0). With this procedure, the measurement result becomes independent of the acoustic absorbency (furnishings) of the specific room in which the measurement is taken.

Acoustics in Simple Words

Imagine you are testing the airtightness of car windows. If you do this in a tunnel (where there is a lot of echo), the noise inside will seem louder than in an open meadow, even with the same windows. The reference difference in levels is like a “mathematical filter” that allows the acoustician to say: “If we were testing this wall under ideal, standard conditions, the result would be this.” This allows us to compare the sound insulation of a wall in a carpet-filled living room with that of a wall in a lovely tiled bathroom and receive a fair verdict regarding the quality of the partition itself, rather than the interior design.

Summary

The reference difference in levels (DnT) is a key parameter in assessing sound insulation in finished buildings. It allows for an objective check to see if walls and ceilings meet building standards, eliminating the impact of whether the room is empty or fully furnished.