The Reference Listening Level of the rooms in which audio engineers mix programmes is very important, as it influences how the audio engineer perceives - and thus mixes - the audio. For many years EBU Tech 3276 and its supplement EBU Tech 3276 s1 have been the recommended way of setting up equipment in professional reproduction rooms, but recent experience has shown that this traditional method is not convenient in the context of loudness normalization and thus should be revised.
New EBU reference noise signal
To help production staff to set up rooms correctly when normalizing to the EBU recommended Loudness Level of -23 LUFS, the EBU specifies that each main loudspeaker should be adjusted to 73 dBC SPL, respectively, when playing back this EBU reference noise signal (500-2000 Hz @ -23 LUFS). The signal is appropriate for average size mixing rooms ranging from 125 to 250 cubic meters.
It should be noted that the reference level used in other types of rooms (e.g. master control rooms) or rooms with different sizes than indicated above may deviate in level. The main requirement in such cases is to consistently use the listening level, so that audio engineers still establish their own 'inner loudness reference'.
More details can be found in paragraph 8.2 of the EBU Guidelines for Production of Programmes in accordance with R 128 (EBU Tech 3343). The reference noise signal is also included in the new version (5) of the EBU Loudness Test Set.