This study reports on subjective and objective acoustical field measurements made in a major survey of 36 Roman Catholic churches in Portugal built in the last 14 centuries. Monaural acoustical measurements (RT, EDT, C80, D50, TS, L, and RASTI) were taken at several source/receiver locations in each church. A group of college students was asked to judge the intelligibility of speech by evaluating live speech at similar locations in each room. This paper complements those presented at the 1996 Indianapolis and Honolulu ASA Meetings and concentrates exclusively on the relationships of the speech intelligibility averaged values with the objective room acoustics measures and with some architectural features of the churches. The averaged results by church are graphed and analyzedby comparisons. Correlation analyses and statistical modeling identified some relationships among the measures. For instance, squared cor- relation coefficients (R2) of 0.67 were found for the relationships: SPEECH-RT AND SPEECH-TS. Between SPEECH and RASTI only a maximum R2 of 0.50 was found. Regarding the churches’ architectural features, the maximum R2 found was 0.52 between SPEECH and NAVE HEIGHT. A general linear model including several architectural features increased the R2 to 0.72. [Work supported by FEUP and ESMAE/IPP–Portugal.] [See NOISE-CON Proceedings for full paper.]
This study reports on subjective and objective acoustical field measurements made in a survey of 36 Catholic churches in Portugal built in the last 14 centuries. Monaural acoustical measurements (RT, EDT. C80, D50. TS and L) were taken at several source/receiver locations in each church and a group of college students was asked to judge the subjective quality of music. The listeners in each church evaluated live music performances at similar locations in each room. Evaluation sheets were used to record the listeners' overall impressions of room acoustic quality and also Loudness, Reverberance. lntimacy, Envelopment, Directionality, Balance, Clarity Echoes and Background Noise. This paper concentrates on the relationships of the subjective pararneters with the objective room acoustics measures and with the architectural features of the churches. Correlation analyses and statistical modeling identified significant relationships among the measures. For instance, linear correlation coefficients ( | R I ) of 0.8-0.9 were found for the relationships: Reverberance/RT and Clarity/C80; the maximum | R | found was 0.93 for Echoes/RT. Regarding architectural features the maximum | R | found was 0.87 between Intimacy and Total Volume.
This study reports on subjective and objective acoustical field measurements made in a survey of 36 Catholic churches in Portugal built in the last 14 centuries. Monaural acoustical measurements (RT, EDT. C80, D50. TS and L) were taken at several source/receiver locations in each church and a group of college students was asked to judge the subjective quality of music. The listeners in each church evaluated live music performances at similar locations in each room. Evaluation sheets were used to record the listeners' overall impressions of room acoustic quality and also Loudness, Reverberance. lntimacy, Envelopment, Directionality, Balance, Clarity Echoes and Background Noise. This paper concentrates on the relationships of the subjective pararneters with the objective room acoustics measures and with the architectural features of the churches. Correlation analyses and statistical modeling identified significant relationships among the measures. For instance, linear correlation coefficients ( | R I ) of 0.8-0.9 were found for the relationships: Reverberance/RT and Clarity/C80; the maximum | R | found was 0.93 for Echoes/RT. Regarding architectural features the maximum | R | found was 0.87 between Intimacy and Total Volume.
Small rooms, such as the ones specifically designed for listening to amplified music, like control rooms in recording studios, face the problem of lowfrequency over-enhancement by acoustic resonances. Several devices have been developed to tackle this problem, such as Helmoltz resonators. The number of controlled acoustic modes depends on several factors among which are the central frequency chosen, the modal density in that frequency range, and the coupling between the resonator and the room. In this paper we suggest that the efficiency of such resonators may be significantly improved if, instead of using basic Helmholtz or devices with uniform cross-section, more complex shapeoptimized resonators are used, in order to cope with a larger number of undesirable acoustic modes. We apply optimization techniques to the uncoupled resonator, developed in our previous work, in order to obtain the optimal shapes for devices that resonate at a design set of acoustic eigenvalues, within imposed physical and/or geometrical constraints. One-dimensional and threedimensional finite element models were implemented. The one-dimensional model was coupled to optimization techniques in order to achieve the design goal. We illustrate the proposed approach with two examples of resonator shapes and different design sets of absorption frequencies. © 2007 Institute of Noise Control Engineering.
The design of musical instruments is still mostly based on empirical knowledge and costly experimentation. One interesting improvement is the shape optimization of resonating components, given a number of constraints (allowed parameter ranges, shape smoothness, etc.), so that vibrations occur at specified modal frequencies. Each admissible geometrical configuration generates an error between computed eigenfrequencies and the target set. Typically, error surfaces present many local minima, corresponding to suboptimal designs. This difficulty can be overcome using global optimization techniques, such as simulated annealing. However these methods are greedy, concerning the number of function evaluations required. Thus, computational times can be unacceptable if complex problems, such as bell optimization, are tackled. Those issues are addressed in this paper, and a method for improving optimization procedures is proposed. Instead of using the (local) parameters Pf(r) as searched variables, the system geometry is modeled in terms of truncated series of orthogonal space-functions Pj(r)=∑najnψjn(r), and optimization is performed on the (global) coefficients ajn. Fourier series and orthogonal polynomials are typical functions ψjn(r). This technique reduces considerably the number of search variables, and has a potential for significant computational savings in complex problems. It is illustrated by optimizing the shapes of both current and uncommon marimba bars.
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