FDTD/K-DWM simulation of 3D room acoustics on general purpose graphics hardware using compute unified device architecture (CUDA)

The growing demand for reliable prediction of sound fields in rooms have resulted in adaptation of various approaches for physical modeling, including the Finite Difference Time Domain (FDTD) and the Digital Waveguide Mesh (DWM). Whilst considered versatile and attractive methods, they suffer from dispersion errors that increase with frequency and vary with direction of propagation, thus imposing a high frequency calculation limit. Attempts have been made to reduce such errors by considering different mesh topologies, by spatial interpolation, or by simply oversampling the grid. As the latter approach is computationally expensive, its application to three-dimensional problems has often been avoided. In this paper, we propose an implementation of the FDTD on general purpose graphics hardware, allowing for high sampling rates whilst maintaining reasonable calculation times. Dispersion errors are consequently reduced and the high frequency limit is increased. A range of graphics processors are evaluated and compared with traditional CPUs in terms of accuracy, calculation time and memory requirements

Studies in modal density – its effect at low frequencies

The ability to objectively measure the reproduction quality of a small room at low frequencies has long been desired. Over many years, there have been attempts to produce recommendations, metrics, and criteria by which to define a particular room. These have often concentrated on some aspect of the modal distribution, such as spacing or density. Other attempts have focused upon the deviation from a desired frequency response. Whilst the subjective validity of objective measures such as these has often been questioned, the notion that a transitional region between a modal and diffuse sound fields exists, dependant on the room volume and reverberation time continues to permeate much thinking. The calculation of this transitional frequency relies on the calculation of a desired modal density. In the case of the most well known definition, the Schroeder Frequency1, the transitional frequency is that point where the density becomes sufficient that three modes lie within one bandwidth. Although this idea may well be useful in some instances, such as defining points for the use of statistical sound field analysis, recent thought has cast some doubt over its relevance as a subjective frequency above which we may ignore modal issues2. This paper highlights a number of studies along with a new listening test, which help us to better understand the role of modal density upon subjective perception of modal soundfields

A study on acoustics of critical audio control rooms

Since the advent of Radio Broadcast that acoustic designers have tried to define a standard for control rooms. Although many years have passed since the first control rooms were built and many different solutions have been tried and tested, a final standard design has not yet been devised. The purpose of this report is to define and demonstrate that a proposed route of investigation will present novelty, address an important issue in this industry and fulfil the necessary requirements for the attainment of a PhD degree. The report is subdivided in chapters. Chapters 2 and 3 are an extended Literature Review of Designs (Chapter 2) and Specifications (Chapter 3) previously published on this type of listening spaces. A detailed description of each paper is given. This is done in order to better identify problems and reasons for specific requirements on Critical listening spaces. Chapter 4 is a personal view of the author on critical listening spaces. It is an organisation of the ideas brought forward in previous chapters, and its relevance is on the identification of generally accepted concepts and their application on the successful design of a critical listening space. Currently accepted design steps are listed. Chapter 5 presents results from a survey performed by the author on a panel of professional recording engineers and producers in the UK. This represents the main subject of this project during the past year. The result of this survey gives an indication of research routes that are important in order to solve eminent problems on the design of critical listening spaces. Finally, Chapter 6 gives a plan of investigation detailing a specific area of research in order to continue this project with the objective of attaining a PhD degree. In this chapter, the author feels that a short literature review should be presented. The reason for another literature review at this stage of the report is mainly to show that previous research done in the field is not comprehensive and therefore leaves scope for further investigation. Additionally, it also indicates which publications will be the basis to start from on the current research. This chapter also presents the relevant points to be investigated, expected results and explains how this will bring originality and novelty to the academic community. Methods to be used, practical work to be carried out and possible problems are described