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This paper discusses the concept of the reverberation radius, also known as critical distance, in rooms with non-uniformly distributed sound absorption. The reverberation radius is the distance from a sound source at which the direct sound level equals the reflected sound level. The currently used formulas to calculate the reverberation radius have been derived by the classic theories of Sabine or Eyring. However, these theories are only valid in perfectly diffused sound fields; thus, only when the energy density is constant throughout a room. Nevertheless, the generally used formulas for the reverberation radius have been used in any circumstance. Starting from theories for determining the reverberation time in nondiffuse sound fields, this paper firstly proposes a new formula to calculate the reverberation radius in rooms with non-uniformly distributed sound absorption. Then, a comparison between the classic formulas and the new one is performed in some rectangular rooms with non-uniformly distributed sound absorption. Finally, this paper introduces a new interpretation of the reverberation radius in non-diffuse sound fields. According to this interpretation, the time corresponding to the sound to travel a reverberation radius should be assumed as the lower limit of integration of the diffuse sound energy.

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This paper describes the design of the Concert Hall of Barcelona, called “L'Auditori”. The acoustical design of the project was finished in 1990 but it was built later and finally opened on 22nd March 1999. The acoustics of the concert hall have been very well received by audiences. In this manuscript, we outline several acoustic features which had to be designed using old methods because the more modern systems had not yet been developed. However, construction was delayed nine years, which meant that new computer tools were available when work was coming to an end in 1990, it allowed us to carry out an overall review of many aspects of the design, A very important issue that required years of research before we discovered the cause of the problem was that musicians could not hear themselves on stage, yet Gade's measurements of ST1 made in 2001 were comparable with those found in the best reference halls. In this paper we discuss this issue, and conclude that the musicians were correct.

The original Orchestra Rehearsal Room of the Great Theater of the Liceu, inaugurated in October 1999, was sufficient to accommodate a medium sized orchestra but it was not suitable for a large orchestra because of its small volume and because the sound produced by the musicians was too loud. This initial deficiency has been corrected in many aspects by applying a new acoustic concept. We developed a 3D-Grid diffuser which resulted in a very significant increase in Reverberation Time and increased the clarity of communication between players and the subjective size of the room volume. 2. ROOM GEOMETRY The volume of the space was marginally increased from 1433 m 3 case 1), (see figure 1a and 1b) to 1748 m 3 case 2), (see figure 2) by removing a lowered ceiling. Acoustic measurements, were made in the space before and after the volume was increased, and then after the labyrinth diffuser was installed case 3) (figures 3 and 4). CASE 1) Rehearsal room before refurbishment Volume of room V: 1433.60 m 3 Floor area: 277.9 m 2 Mean height: 5.16 m The wood ceiling (shown in red) was removed, and the volume increased marginally-see case 2): CASE 2) Rehearsal room during refurbishment (without diffuser) New volume of room: 1747.99 m 3 Floor surface: 277.9 m 2 Mean height: 6.29 m 46 The Refurbishment of the Orchestra Rehearsal Room of the Great Theater of Liceu