Experimental Investigation of the Use of Equivalent Sources Model in Room Acoustics Simulations

As an alternative to models based on geometrical acoustics and the computationally intensive Finite Element or Boundary Element methods, the Equivalent Sources Model (ESM) has recently been modified and extended from its original application in acoustical holography to room acoustics simulations. Previous numerical simulation results have demonstrated the advantages of room acoustics ESM’s (especially when higher order sources are used as its equivalent sources) as a flexible reduced order modeling procedure in room acoustics. In the present work, an experimental investigation of the room acoustics ESM was conducted in which the sound field generated by a loudspeaker in a small room was measured. The ESM prediction of total sound field in the room is calculated by coupling a free-space ESM (which gives the source information) with a room acoustics ESM (to account for the room effect). The ESM predictions are compared with the measurements to show the validity of the room acoustics ESM in a realistic application

Real-time Evaluation of Room Acoustics using IFC-based Virtual Reality and Auralization Engines

Virtual Reality and Auralization are commonly used for separate types of simulation and evaluation in todays’ building industry. Combining the two technologies in order to evaluate room acoustics through real time auraliza-tion is, however, still a novel approach in the industry. Through a case study of a major engineering company with branch offices in both Denmark and Norway, we identified common practises in designing room acoustics, used in the developing of a combined audio-visual system. The system is devel-oped to support dialog between designers and end-users, with no or limited expertise in designing room acoustics. The system is, additionally, developed to widen the use of virtual reality with auralization, by providing a tool mak-ing such use possible.Virtual Reality and Auralization are commonly used for separate types of simulation and evaluation in todays’ building industry. Combining the two technologies in order to evaluate room acoustics through real time auraliza-tion is, however, still a novel approach in the industry. Through a case study of a major engineering company with branch offices in both Denmark and Norway, we identified common practises in designing room acoustics, used in the developing of a combined audio-visual system. The system is devel-oped to support dialog between designers and end-users, with no or limited expertise in designing room acoustics. The system is, additionally, developed to widen the use of virtual reality with auralization, by providing a tool mak-ing such use possible

Loudness of the singing voice: A room acoustics perspective

This thesis is examining ectophonic (sounds created outside the human body) and autophonic (sound from one’s own voice) loudness perception for the operatic voice, within the context of room acoustics. Ectophonic loudness perception was modelled within the context of room acoustics for the operatic voice in chapter two. These models were then used to explore the loudness envelope of the messa di voce (MDV), where psychoacoustically based measures were shown to perform better than physical acoustic measures used in previous studies. The third chapter addressed autophonic loudness perception, while presenting limitations in modelling it in a manner similar to ectophonic loudness models. Some of these limitations were addressed in chapter four with two experiments where autophonic loudness of opera singers was explored using direct psychoacoustical scaling methods, within simulated room acoustic environments. In the first experiment, a power law relationship between autophonic loudness and the sound pressures produced was noticed for the magnitude production task, with different power law exponents for different phonemes. The contribution of room acoustics for autophonic loudness scaling was not statistically significant. Lombard slope, as it applies to autophonic perception and room acoustics was also studied, with some evidence found in support. The second experiment in chapter four explored autophonic loudness for more continuous vocalisations (crescendi, decrescendi, and MDV) using adapted direct scaling methods. The results showed that sensorimotor mechanisms seem to be more important than hearing and room acoustics in autophonic loudness perception, which is consistent with previous research. Overall, this thesis showed that the room acoustics effect on the loudness of the singing voice needs to be assessed based on the communication scenario. This has relevance for voice analysis, loudness perception in general, room acoustics simulation, and vocal pedagogy

Surface diffusion coefficients for room acoustics : free-field measures

A surface diffusion coefficient is needed in room acoustics to enable the quality of diffusing surfaces to be evaluated. It may also facilitate more accurate geometric room acoustic models. This paper concentrates on diffusion coefficients derived from free-field polar responses. An extensive set of two- and three-dimensional measurements and predictions was used to test the worth of different diffusion coefficient definitions. The merits and problems associated with these types of coefficients are discussed, and past parameters reviewed. Two new coefficients are described. The new measure based on the autocorrelation function is forwarded as the best free-field coefficient. The strengths and weaknesses of the coefficient are defined. © 2000 Acoustical Society of America

Efficient Synthesis of Room Acoustics via Scattering Delay Networks

An acoustic reverberator consisting of a network of delay lines connected via scattering junctions is proposed. All parameters of the reverberator are derived from physical properties of the enclosure it simulates. It allows for simulation of unequal and frequency-dependent wall absorption, as well as directional sources and microphones. The reverberator renders the first-order reflections exactly, while making progressively coarser approximations of higher-order reflections. The rate of energy decay is close to that obtained with the image method (IM) and consistent with the predictions of Sabine and Eyring equations. The time evolution of the normalized echo density, which was previously shown to be correlated with the perceived texture of reverberation, is also close to that of IM. However, its computational complexity is one to two orders of magnitude lower, comparable to the computational complexity of a feedback delay network (FDN), and its memory requirements are negligible