Mixing consoles, which are usually of large dimensions, are essential equipment in a mixing room of a production studio. This large obstacle always has to be placed nearby the listening position in a mixing room. A significant dip at around 100 Hz is often observed on the monitoring response, the transfer function from the loudspeaker to the listening position, in a small/medium sized mixing room. This paper studies the relationship between the dip at around 100 Hz and the effect of the presence of the mixing console. The generating mechanism of the dip is investigated by numerical simulations and experimental measurements. The results show that the reflection sound from the floor and the behavior of the mixing console as a cross over filter are important when considering the dip. Examples of trials for improvement of the dip are also examined.
Measurements that attempt to predict the perceived spatial impression of musical signals in concert halls typically are conducted by calculating the interaural cross-correlation coefficient (IACC) of an impulse response. The causes of interaural decorrelation are investigated and it is found that this is affected by frequency dependent interaural time and level differences and variations in these over time. It is found that the IACC of impulsive and of narrowband tonal signals can be very different from each other in a wide range of acoustical environments, due to the differences in the spectral content and the duration of the signals. From this, it is concluded that measurements made of impulsive signals are unsuitable for attempting to predict the perceived spatial impression of musical signals. It is suggested that further work is required to develop a set of test signals that is representative of a wide range of musical stimuli.
A modally-reactive panel in a room absorbs and radiates sound at the same time when it is excited acoustically by the enclosed sound field. The absorption of sound occurs when only part of the incident sound is reflected by the panel, but when the entire panel vibrates, the radiation of sound is also produced. In this paper, Statistical Energy Analysis (SEA) is used to establish a relationship between the acoustic-structural coupling of the panel with the sound field and the Sabine absorption coefficient of the panel. It is shown that the coefficient does not only consist of the sound absorption by the panel from the room but also, the sound radiation from the vibrating panel back into the room. Computational and experimental examples are presented for different acoustical properties of the panel and the sound field to illustrate the extent of influence of the sound radiation on the coefficient. The results provide a basic understanding of the conditions in both cases where the sound radiation has significant effects and negligible effects on the determination of the Sabine absorption coefficient of modally-reactive panels in rooms.
A method of predicting the area effect of an absorbent surface with finite dimensions by using a boundary integral equation is proposed and the reason why the area effect occurs is shown. In order to check the effectiveness of the method, some experiments are carried out in a reverberation room. These results are in good agreement with those obtained numerically from the proposed method.
Representative values of acoustical parameters in rooms for music performance are obtained from measurements in many halls. Discussed are the effects of source locations and positions of receivers on the results. The parameters studied are reverberation time RT, early decay time EDT, strength G, clarity C80, and interaural-cross-correlation coefficient IACC, which were measured using identical procedures, and where possible, according to international standard ISO 3382. Separate ranges and positions are suggested for symphony halls, chamber music halls and opera houses. It is indicated that the minimum number of positions given in ISO 3382 should be exceeded when measuring some parameters.
In order to evaluate the scattering coefficients of architectural surfaces, a numerical technique based on Mommertz’s definition is developed with employing a 3-dimensional boundary element method. Numerical examination on the setting of parameters in computation and the conditions of samples is performed so as to ensure accurate calculation with this technique. As a result, criteria for the numerical parameters and for the test arrangement are clarified, and additionally, illustrating the behavior of directional and random-incidence scattering coefficients. Furthermore, in comparison between the values with the present method and those for an infinite periodic surface, general correspondence is confirmed although some differences appear due to the edge diffraction by the finite sample.
The basic principle of common room acoustics computer models is the energy-based geometrical room acoustics theory. The energy-based calculation relies on the averaging effect provided when there are many reflections from many different directions, which is well suited for large concert halls at medium and high frequencies. In recent years computer modelling has become an established tool in architectural acoustics design thanks to the advance in computing power and improved understanding of the modelling accuracy. However concert hall is only one of many types of built environments that require good acoustic design. Increasingly computer models are being sought for non-concert hall applications, such as in small rooms at low frequencies, flat rooms in workplace surroundings, and long enclosures such as underground stations. In these built environments the design issues are substantially difference from that of concert halls and in most cases the common room acoustics models will needed to be modified or totally re-formulated in order to deal with these new issues. This paper looks at some examples of these issues. In workplace environments we look at the issues of directional propagation and volume scattering by furniture and equipment instead of the surface scattering that is common assumed in concert hall models. In small rooms we look at the requirement of using wave models, such as boundary element models, or introducing phase information into geometrical room acoustics models to determine wave behaviours. Of particular interest is the ability of the wave models to provide phase information that is important not only for room modes but for the construction of impulse response for auralisation. Some simulated results using different modelling techniques will be presented to illustrate the problems and potential solutions.
In order to investigate the effect of a hall response on music players, we have made various experimental studies up to now. In order to develop this research, one of the most important subjects is to understand the musicians’ perception of the acoustic effects of halls. Musicians generally perceive the acoustic properties of a concert hall by keeping their performing action and by adjusting their playing technique subconsciously. This kind of interactive relationship between musicians and acoustic environment is really important when considering the acoustic values of concert halls for musicians. In this study, musicians’ awareness of concert halls was investigated through interview survey and the cognitive psychological phenomena of musicians were interpreted by applying the “tacit knowing” theory. Then the process to extract the musicians’ perception in experimental studies on concert hall acoustics is discussed.
The current version of the standard ISO 3382 has now been in existence for seven years, yet for many the contents of Annexes A and B on newer measures remain confusing. A major issue is the use to which these measures are put. Where the ‘new’ measures for auditoria differ from other acoustic parameters is that they refer to a range of subjective effects, which are perceived simultaneously. Using the newer measures requires a good understanding of the multi-dimensional nature of music perception. Measurement data requires interpretation. When measurements are made in unoccupied auditoria, the data requires correction to the situation with full audience. Another issue is how to condense data measured across audience areas. The simplest approach is to present mean values of the different quantities, but this ignores the fact that many quantities vary significantly with location; the disappointment of sitting in a poor seat in an auditorium is no less for the knowledge that the overall mean is good. Several of these issues are discussed here with the aim of promoting more uniformity in the way the objective measures proposed in the Standard are applied by different research groups and companies.
Application of the ISO 3382 standard can lead to the acquisition of large amounts of data describing conditions in a hall. The data could include the values of a number of measures at 6 or more octave band frequencies and for many combinations of source and receiver location. This paper discusses and gives examples of using this data to find important acoustical features. The amount of data can be reduced by calculating average values over the entire data set or for each sub-area of the hall. Various important spatial variations can often be better understood from plots of values versus source-receiver distance. The analysis approach will depend on the purpose of the study, which could be for comparisons with various criteria, for investigations of problems, or to better understand the acoustical properties of the hall. The significance of new measurements can be determined by comparing values: with proposed ideal criteria, with values in well-known halls, or with theoretical predictions. The importance of differences between two values should be considered in terms of published just noticeable differences for particular measures. Separately examining early- and late-arriving sound levels can be a useful diagnostic tool for better understanding the acoustical properties of halls.
There has been a demand for measuring the degree of interaural cross-correlation (ICC) as a physical measure for auditory (apparent) source width (ASW). Standardization of the measurement has been also discussed by ISO. One of the important problems in measurements of ICC is the selection of frequency bandwidth. Following ISO, ICC is defined with a wide frequency band and generally measured in 1/1 octave bands. This paper reports two experiments that compare ASW with ICC measured by different methods, so as to determine the best physical measure in terms of correlation with the subjective effect. The experimental results show that the use of 1/3 octave bandwidth is preferred to the use of a wide bandwidth and 1/1 octave bandwidth for measuring ICC as a physical measure of ASW.
In order to describe the acoustics of enclosed spaces and to quantify the properties of sound fields, single number parameters are commonly used. These are calculated from impulse responses which were previously recorded with special microphones. Even though current research suggests that most parameters vary severely from one listening position to another in the same sound field, there is currently only a rough concept regarding if and how changes in these parameters are perceived. Aim of this study is to derive the difference limen for aspects of spatial impression in regard to their absolute value. In two steps sound fields of different auditoria are being recorded in different listening positions with suitable microphones and, at the same position, with an artificial head. In listening tests listeners are being asked to judge apparent source width and envelopment of binaurally presented sound fields. These statements are used to derive the difference limen for the corresponding parameters.
The definition and measurement of sound spatialisation have been strongly enhanced in last years, as nowadays spatial properties of sound propagation are considered quite important during design of auditoria. Besides, a proper description of spatiality is requested during virtual audio reproduction of sound quality in dedicated listening rooms for 3D reproduction purposes. Normally, only binaural measurements are performed, by means of a dummy head, even though international standards like ISO 3382 require measuring some spatial parameters (i.e. LE, LF, IACC). 3D impulse responses are rarely measured and utilised for sound reproduction. In this paper, an innovative procedure of measuring spatial sound characteristics is presented. The application of this new technique in virtual 3D sound reconstruction is emphasized. Furthermore, the methodology is compared with other techniques of 3D sound reproduction. Finally, the results of a wide campaign of measurements of spatial parameters among different auditoria all over the world, and conducted with the novel methodology, are compared with the results of standard binaural and 3D measurements. The possibility to enhance the spatial reproduction of sound quality in real spaces and the comprehensibility of spatial parameters is then considered and presented in different cases.