1	Acoustics 08 Experimental analysis of the acoustical behaviour of Musikverein in concert and ballet configurations A. Farina, D. E. Commins and N. Prodi (a) University of Parma, Via delle Scienze 181/A, Industrial Engineering Dept., 43100 Parma, Italy (b) Commins Acoustics Workshop, 15 rue Laurence Savart, 75020 Paris, France (c) Engineering Dept. - Univ. of Ferrara, Via Saragat, 1, 44100 Ferrara, Italy
2	Topics Configurations of the room Standard room acoustics measurements Coupling with the storage space under the stalls Surface intensity measurements Analysis of the results
3	Concert configuration
4	Concert configuration
5	Ballroom configuration
6	Ballroom configuration
7	Measurement method: Exponential Sine Sweep
8	Exponential Sine Sweep method x(t) is a sine signal, which frequency is varied exponentially with time, starting at f₁ and ending at f₂.
9	Test Signal – x(t)
10	Measured signal - y(t) The not-linear behaviour of the loudspeaker causes many harmonics to appear
11	Inverse Filter – z(t) The deconvolution of the IR is obtained convolving the measured signal y(t) with the inverse filter z(t) [equalized, time-reversed x(t)]
12	Deconvolution of Exponential Sine Sweep The “time reversal mirror” technique is employed: the system’s impulse response is obtained by convolving the measured signal y(t) with the time-reversal of the test signal x(-t). As the exp. sine sweep does not have a “white” spectrum, proper equalization is required
13	Result of the deconvolution The last impulse response is the linear one, the preceding are the harmonics distortion products of various orders
14	IR Selection After the sequence of impulse responses has been obtained, it is possible to select and insulate just one of them:
15	Maximum Length Sequence vs. Sweep
16	Hardware: loudspeaker & microphone
17	Equipment: computer & sound interface
18	Directivity of transducers LookLine D200 dodechaedron
19	pressure-velocity microphone The Soundfield microphone allows for simultaneous measurements of the omnidirectional pressure and of the three cartesian components of particle velocity (figure-of-8 patterns)
20	Directivity of transducers
21	Measurement method: B-format Impulse Response
22	3D Impulse Response (Gerzon, 1975)
23	Measurement positions
24	ISO3382 Parameters
25	Results
26	Results
27	Results
28	Results
29	Results
30	Storage room under the stalls
31	Sound reduction index
32	Reverberation time of storage room (empty)
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35	Conclusions Musikverein is a truly variable acoustics room The Ballroom configuration exhibit reverberation times significantly larger than the Concert configuration, particularly at medium frequencies Also G is significantly different However, C80 and LF do not change remarkably, ensuring good acoustical quality also in Ballroom configuration The storage room under the stalls is heavily insulated, hence it cannot have any effect The effect of the audience should be taken into account, particularly in Ballroom configuration, where it would be probably much larger than in Concert configuration.