Relation of acoustical parameters with and without audiences in concert halls and a simple method for simulating the occupied state

Five acoustical parameters-reverberation time RT, early decay time EDT, clarity C80, strength G, and interaural cross-correlation coefficient IACC-were measured using identical procedures with and without audiences in six concert and opera halls. Reverberation times without audiences were measured in 15 additional halls using the same measuring techniques as for the six halls above, but for full occupancy the data were taken from musical stop chords at symphonic concerts. This paper shows that in all halls (1) the occupied RT can be predicted from the unoccupied RT using a linear regression equation, y = a - b exp(x), within acceptable limits, at low- and mid-frequencies. It is also shown for the six halls that (2) occupied C80's are predicted accurately from unoccupied values by the newly proposed equation; (3) G's with and without audiences are highly correlated by a first degree linear regression equation; and (4) IACCs have nearly the same value in both occupied and unoccupied halls. As a separate subject, the successful use of a cloth covering for seats in a concert or opera hall to simulate the occupied condition has been developed.     

Acoustic Features of Organ Concert Halls: Trends and Problems

Acoustical Physics - The main acoustic requirements in organ concert halls, their evolution in recent decades, and the problems arising in the creation and rebuilding of these halls are considered....     

On the combined effects of early- and late-arriving sound on spatial impression in concert halls

This paper describes six new experiments involving subjective ratings of the listener envelopment, LEV, and the apparent source width, ASW, of simulated sound fields. Previous work has identified LEV and ASW as the principal components of spatial impression in concert halls and has shown that ASW is primarily influenced by the level of early lateral reflections and LEV by late-arriving lateral reflections. The new results in this paper show that LEV can result from nonlateral late-arriving sounds and demonstrate the conflicting effects of early- and late-arriving lateral sound on ASW and LEV when both are present, as would occur in real halls. While it is possible to create simulated sound fields with only either LEV or ASW, in typical concert halls, the balance between early- and late-arriving lateral sound will determine the relative importance of LEV and ASW. LEV and ASW are shown to be perceived when the critical components of the sound field are salient relative to other components. The results of the new subjective studies were used to estimate expected ASW and LEV in 16 halls. In these halls LEV is predicted to be the stronger component of spatial impression.     

A group of objective acoustical criteria for concert halls

To establish a definite list of the most important objective criteria for concert halls is not easy, but it is suggested that a group of four or five criteria may be sufficient to characterise, in general, the ‘acoustics’ of a specific hall. Comparing various concert halls by means of their measured objective criteria indicates that a rather simple method of ranking is feasible.     

Wall diffuser designs for acoustical renovation of small performing spaces

This paper investigates the material characteristics of diffusers for acoustical renovation of existing small performing spaces. Consideration is given to acoustical effects on sound fields through the practical cases of two performing halls: the Chamber Hall (450 seats) and the M-Theater (630 seats) in the Sejong Performing Arts Center, Seoul. The Chamber Hall was completely refurbished into a recital hall from its previous shape of a rectangular conference space. The saw-tooth shaped wall diffuser profile in the Chamber Hall was designed using glass-fiber reinforced concrete for mid-frequency sound diffusion. The M-Theater was renovated as a live and intimate space for dramatic performances with a design that included more seats on the upper floors and additional spaces above ceiling reflectors. The vertically-patterned diffuser profile with protruded cubic surfaces in the M-Theater was designed using glass-fiber reinforced gypsum for sound diffusion in the major speech frequency range. Designed diffuser profiles were evaluated for both halls by measurements of scattering and diffusion coefficients of the 1:10 scale model diffusers. The effects of diffusers in both halls were also investigated by covering the lateral walls close to the stages with reflective materials to control diffusive surfaces. As a result, spatial uniformity increased with diffusive wall profiles in both halls.     

Influence of source directivity on noise levels in industrial halls: Simulation and experiments

Noise exposure of workers in industrial halls is mainly induced by noisy machines whose acoustical features are often globally known by Sound Pressure Level. The evaluation of the directivity of these noise sources can help to anticipate specific solutions for noise reduction.This study shows how the directivities of three wood-working machines have been characterized. Some characterisations have been achieved with a simple and fast acoustical intensity mapping which meets the constraints of industrial areas.When source directivity is evaluated, its influence on the noise field in industrial halls can be assessed. Some simulations and some experiments allowed the estimation of the noise field induced in workshops by both directional and omnidirectional sources. Comparison of the fields prove that the noise distribution is influenced by the source directivity if the halls are empty. As soon as the halls contain scattering objects, the directivity effect is reduced a lot and the noise field remains nearly the same far from the source whatever source used. Nevertheless, workers close to a machine are exposed to noise according to their position with respect to the machine. Exposure at the workplace can vary from 4 to 8 dB(A) according to the directivity of machines such as those measured in the trials.     

音乐厅音质设计

本文简要介绍音乐厅建筑实践的发展史和四个最近设计成功的大厅。简要叙述现在于大厅内能测量且与主观响应有关的客观参数，即混响时间、初始时间延迟间隙、响度、扩散、侧向反射和早期对后期能量比。最后，简短地报道近来声场模拟方法的发展，用这些方法可以预测某些声学特性。     

Monaural and binaural parameters of Rudolfinum concert halls in Prague

Objective parameters for the evaluation of the Rudolfinum concert hall in Prague, Czech Republic are the focus of the present article. The measured results for Reverberation parameters, Energy parameters, Intelligibility parameters, and Spatial parameters of the building’s two halls are presented and discussed including a comparison with recommended values or theory, as well as several unique architectural and acoustical qualities of the halls. The early lateral energy fraction parameter is measured by the intensity probe method discussed in the supplement. The performance is verified by tests in anechoic and reverberant rooms.     

活动场所的语言清晰度和鸡尾酒会效应

本文讨论人们活动场所的语言清晰度，鸡尾酒会效应和它对语言清晰度的影响，对会议厅，剧院，教室，侯机大厅，侯车厅，体育馆，溜冰场等处的测量和清晰度试验，建立了主观评价和清晰度得分关系并给出一些这类场所不引起鸡尾酒会效应的允噪声级阈值，最后讨论了鸡尾酒会效应的计算机模型。     

Taking account of loudness constancy for the loudness criterion for concert halls

One of the surprises from analysis of results of an objective and subjective study of British concert halls (1988 Acustica 66, 1–14) was that the subjective judgement of loudness in concert halls is influenced not only by sound level but also by the source–receiver distance. This response implies that the same sound level is judged louder at positions further from the orchestra platform. Whereas level decreases with distance in actual halls, loudness is judged more-or-less independent of position in average halls (except at positions close to the platform and seats overhung by balconies). As an observation it ties in with evidence from experimental psychologists for loudness constancy throughout a space. The sound strength G is the sound level in an auditorium normalised to the sound power level of the source; the traditional criterion of acceptability for level is that G ? 0 dB. The paper proposes that, on the basis of subjective evidence and objective behaviour in auditoria, the criterion for G should not be a unique value of G but rather a function of source–receiver distance.     

座位数在音乐厅和歌剧院计算中的作用

在对Leo Beranek著《音乐厅和歌剧院》一书中所提供的80余所音乐厅和歌剧院声学参数的测定结果数据分析的基础上,经过简单的数学处理和简化,提出一些个人见解:强度因子G和座位数N的关系;对于N小于和等于2000的音乐厅,空场早期衰变时间EDT等于空场混响时间。文中给出在N＜ 2000的情形下空场EDT的计算。座椅数是决定厅堂容积的出发点,由此做出两个厅堂的初步设计实例。      

Structures symplectiques sur les espaces de courbes projectives et affines

A symplectic structure on the space of nondegenerate and nonparametrized curves in a locally affine manifold is defined. We also consider several interesting spaces of nondegenerate projective curves endowed with Poisson structures. This construction connects the Virasoro algebra and the Gel'fand-Dikii bracket with the projective differential geometry.     

Room acoustical parameters: A factor analysis approach

In this study, we determined the most representative acoustical parameters for halls intended for verbal or music audition. Our study was carried out in nine halls of different shapes and designed for different uses. We measured the impulse response at a great number of points (many more than the minimum required by the ISO 3382 norm). From a physical viewpoint, all halls are enclosed three-dimensional areas. Our work hypothesis is that objective (measurable) acoustical parameters, or a combination of such parameters, must provide the acoustical information specific to each hall and must make it possible to grade each hall. Factor analysis was used to obtain these grading parameters and the considerable number of measurements we determined guaranteed the application of this type of analysis. The convergence provides corroboration of the main correlations between parameters. A group of orthogonal parameters was thus obtained, made up of three factors that group the parameters used by different outstanding researchers. These factors provide a clear acoustical interpretation. We have termed the first of these “intelligibility” as it contains intelligibility parameters; the second is associated with spaciousness; the third and last parameter has been termed “strength” as it is a linear combination of the parameters that measure the amplification (G) and the bass ratio (BR). The optimal scores of these factors for different uses of halls make it possible to grade any hall, independently of its shape, for its corresponding use.     

Etude par spectrometrie Raman des complexes de l'iode dans les alcools et les ethers

Laser Raman spectra of iodine-alcohol and iodine-ether solutions have been studied. It was found a new line at 167 cm^?1 for alcohols and at 170 cm^?1 for ethers which is tentatively attributed to an intermediate Hassel complex.     

Audience noise in concert halls during musical performances

Noise generated by the audience during musical performances is audible and sometimes disturbing. In this study, an attempt to estimate such audience noise was carried out. From the recordings of performances in five performance spaces (four concert halls and one opera house), probability density functions of the sound pressure levels were obtained in octave bands, which were fitted with three Gaussian distribution curves. The Gaussian distribution curve with the lowest mean value corresponds to a mixture of the technical background noise and audience generated noise, which is named the mixed background noise. Finally, the audience noise distribution is extracted by energy subtraction of the technical background noise levels measured in an empty condition from the mixed background noise levels. As a single index, L(90) of the audience noise distribution is named the audience noise level. Empirical prediction models were made using the four orchestra concert halls, revealing that the audience noise level is significantly correlated with the technical background noise level. It is therefore concluded that a relaxation of the current background noise recommendations for concert halls is not recommended.     

Engaging concert hall acoustics is made up of temporal envelope preserving reflections

Strong, exciting, and engaging sound is perceived in the best concert halls. Here, it is shown that wideband early reflections that preserve the temporal envelope of sound contribute to the clear and open acoustics with strong bass. Such reflections are fused with the direct sound due to the precedence effect. In contrast, reflections that distort the temporal envelope render the sound weak and muddy because they partially break down the precedence. The presented findings are based on the earlier psychoacoustics research, and confirmed by a perceptual evaluation with six simulated concert halls that have same monaural room acoustical parameter values according to ISO3382-1.     

Sound strength and reverberation time in small concert halls

Sound strength and reverberation time measurements have been carried out in six small concert halls in Cambridge, UK. The sound strength G is a measure of the physical sound level in a concert hall and is closely related to the subjective sensation of loudness. It compares integrated impulse responses at a point in the measured room with that measured at ten metres distance in the free field.The aim of the measurements is to investigate the acoustic characteristics of the halls concerning sound strength and reverberation time. Furthermore the effect of the variable acoustics in the halls on these parameters is discussed in this paper. Especially for bigger ensembles it is often desirable to reduce the sound level in a small concert hall. The measurement results show that for a fixed hall volume, this can primarily be achieved by decreasing the reverberation time in the hall. However, with regard to the sound quality of a hall and the recommended reverberation times for chamber music, reverberation time cannot be reduced by an arbitrary extent. Therefore reverberation time and strength have to be balanced very carefully in order to obtain sufficient reverberation whilst at the same time avoiding excessive loudness. Finally the measured strength levels are compared to values derived from traditional and revised theory [Barron M, Lee L-J. Energy relations in concert auditoriums. J Acoust Soc Am 1988;84(2):618-28] on strength calculations in order to assess the accuracy of the theory for small chamber music halls. Possible reasons for the low measured strength levels observed are discussed with reference to related design features and objective acoustic parameters.     

Facteurs de structures partiels et grandeurs thermodynamiques dans les alliages liquides

From the calculation of partial structure factors in liquid alloys developed by Bhatia and Thornton, the authors establish a generalized relationship between these structure factors and the thermodynamic parameters in dilute solutions by introducing Wagner's interaction coefficients. The validity of using models describing the interactions in solution to establish such relationship is discussed.     

Subjective preference tests for sound fields in concert halls simulated by the aid of a computer

In the context of optimal acoustic design of concert halls, preference tests for simulated sound fields with various combinations of early discrete reflections and subsequent reverberation were conducted and the results compared with objective parameters. The results show that lateral early reflections which yield a small value of the interaural cross correlation give more preferred judgments than do non-lateral ones. The most preferred initial time delay (or scale factor for the dimensions of concert halls) can be determined by the long-time autocorrelation function of a music motif and by the total amplitude of both early reflections and the subsequent reverberation. As a comprehensive design concept, an “overall preference” for listeners is introduced here from the preference results.     

Analysis of Sabine and Eyring equations and their application to concert hall audience and chair absorption

Historically, two equations have been used for predicting reverberation times, Sabine and Eyring. A precise means is presented for determining Eyring absorption coefficients alpha(eyring) when the Sabine coefficients alpha(sabine) are known, and vice versa. Thus, either formula can be used provided the absorption coefficients for the Sabine formula are allowed to exceed 1.0. The Sabine formula is not an approximation to the Eyring equation and is not a shortcoming. Given low reverberation times, the ratio of alpha(sabine) to alpha(eyring) may become greater than 2.0. It is vital that, for correct prediction of reverberation times, the absorption coefficients used in either formula must have been determined in spaces similar in size and shape, with similar locations of high absorption (audience) areas, and with similar reverberation times. For concert halls, it is found that, when the audience area (fully occupied) and midfrequency reverberation time are postulated, the hall volume is directly proportional to the audience absorption coefficient. Approximately 6% greater room volumes are needed when choosing nonrectangular versus classical-rectangular shaped halls and approximately 10% greater volumes when choosing heavily upholstered versus medium upholstered chairs. Determinations of audience sound absorption coefficients are presented, based on published acoustical and architectural data for 20 halls.