Church, Worship Facility

Church of San Gerardo hospital

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On April 14, 2012 the church of the new San Gerardo hospital in Monza - designed by the architect Edrisio Bruletti - was inaugurated. As soon as the concrete structure was built, strong reverberation and resonance problems appeared deriving from the particular geometry of the room. Therefore, we intervened with an acoustic treatment proposal, flanked by Mauro Lavazza of Leading Technologies - for electric sound system - and the GGP Sound Alberto Ferraris for the installation of the sound absorbing false dome.

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When we have been called, only the concrete structure was done: the church had obvious acoustic problems because of the focusing effect of the dome. It was so annoying that it was impossible to catch the words of a person placed at over a meter and a half away. With the first acoustic surveys we measured extremely long T30 reverberation time values, of about 12 s, especially at low and low-medium frequencies. The situation looked rather critical especially considering that, at the time of the first measures, the room was not entirely closed, since it lacked doors and windows (for a total of at least 1/3 of the entire lateral surface).

The acoustic treatment design that we presented with the architect Edrisio Bruletti was based on three interventions:

  1. creation of a false ceiling in the shape of an inverted dome inside the dome: the system works as a low frequencies trap. This surface is convex and not concave, so it spreads the acoustic field homogeneously and not concentrated as before. The inside of the false dome is filled with sound-absorbing material and its surface is in perforated wood;
  2. coating of the walls with sound-absorbing plaster;
  3. choice of the sound diffusion system: a JBL CBT100LA line array. We made this choice for the efficiency of speakers in the reproduction of speech, for the narrow angle of vertical spread (which is useful not to work the dome in a negative way) and for the ease of inclination and mounting. We set up 4 speakers looking for the best way to create a homogeneous sound field throughout the church.

Details

Architectural design: Arch. Edrisio Bruletti Audio: Leading Tech. Inverted dome: GGP Sound

Info
Details
Architectural Acoustics Church, Worship Facility
Rooms The church
Audio System JBL CBT100
Layout Layout
Planimetria - Church of San Gerardo hospital
The church
Area 300 m2 Volume 1200 m3
Reverberation time Ante-operam 11s; Post-operam 2.7s sala vuota, 1.9s sala piena
Description
The results we obtained after the acoustic correction were optimal: under the dome we measured reverberation times of about 2.5 s at 500 Hz. It should also be considered that we measured the empty room, without people nor furnishing. The full room reverberation times will be even lower (about 1.8 √∑ 2.2 s at 500 Hz) and perfectly in line with the acoustic CAD simulated results. The coloring of the reverberation seemed also much more natural, with a perfect balance of mid and high frequencies; before the correction we had the maximum sound energy at medium-low frequencies (which were the most emphasized by the "focus" of the dome), while the highest were damped, and thus speech intelligibility was affected.

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