AES Los Angeles 2014
Paper Session P11
P11 - Room Acoustics
Saturday, October 11, 9:00 am — 11:30 am
Doyuen Ko, Belmont University - Nashville, TN, USA
P11-1 Development of a Sound Field Diffusion Coefficient—Alejandro Bidondo, Universidad Nacional de Tres de Febrero - UNTREF - Caseros, Buenos Aires, Argentina; Mariano Arouxet, Universidad Nacional de Tres de Febrero - Buenos Aires, Argentina; Sergio Vazquez, Universidad Nacional de Tres de Febrero - Buenos Aires, Argentina; Virtual Things; Javier Vazquez, Universidad Nacional de Tres de Febrero - Buenos Aires, Argentina; Germán Heinze, Universidad Nacional de Tres de Febrero - Buenos Aires, Argentina; Adrián Saavedra, Universidad Nacional de Tres de Febrero - Buenos Aires, Argentina
This research addresses the development of an absolute descriptor and its associated calculation software algorithm with user interface, which quantifies the degree of diffusion, in a third octave band basis and globally, of a sound field from a monaural impulse response. The degree of sound field diffuseness is related with the probability of getting accumulated energy in discrete reflections compared to the total energy contained in all the reflections of an impulse response, after extracting its decay and normalizing it in respect to its reverberation time. The coefficient range varies between 0 and 1, zero being “no diffuseness” and one being a maximum absolute reference obtained from analyzing different types of rooms. The challenge has been not only to develop this coefficient theoretically but converting its theory in a mathematical numerical calculation through a dedicated software. This coefficient may be used both to study the effects of sound diffusers coatings as well as coated surfaces and the degree of perception of different values which may appear within sound fields.
Convention Paper 9155
P11-2 Simulating Talker Directivity for Speech Intelligibility Measurements—Peter Mapp, Peter Mapp Associates - Colchester, Essex, UK
The research investigated how both the frequency response and directivity of a talker or voice simulator can affect the measured and predicted speech intelligibility within a given situation. Current sound system and acoustic standards provide little guidance as to the required acoustic characteristics of a simulator or the effects that its directivity and frequency response parameters may have. It is shown that the both driver size and format as well as the overall frequency response can have a marked effect on speech intelligibility measurements. A range of talker loudspeaker simulators was investigated in both real and simulated environments. The research shows that the characteristics of several commonly used simulators varied significantly which markedly affected the resultant intelligibility measurements. The results of the work are used to formulate a number of recommendations for talker and voice simulator electroacoustic characteristics and standardization of measurement methods.
Convention Paper 9156
P11-3 Visualization of Early Reflections in Control Rooms—Malcolm Dunn, Marshall Day Acoustics - Auckland, New Zealand; Daniel Protheroe, Marshall Day Acoustics - Auckland, New Zealand
Measurements were undertaken in a variety of control rooms with a system utilizing a compact microphone array and sound intensity technique to estimate the direction of early reflections. This paper presents the results of these measurements including 3D intensity plots that provide a visual representation of sound arrivals at the listener position. The effectiveness of this type of system for the detection of problematic reflections and the evaluation of the listening environment is discussed.
Convention Paper 9157
P11-4 Holistic Acoustic Absorber Design: From Modeling and Simulation to Laboratory Testing and Practical Realization—Rob Toulson, Anglia Ruskin University - Cambridge, UK; Silvia Cirstea, Anglia Ruskin University - Cambridge, UK
In developing a new acoustic absorber, a number of practical design challenges are experienced. Complex mathematical models for many acoustic absorbing methods have previously been developed, however there is very little accessible data describing how those models perform in a practical implementation of the design. This project describes a holistic approach to the development of a novel slotted film sound absorber and presents the results at each design iteration. Initially a number of mathematical models are considered, in order to optimize the design geometry for a maximum sound absorbing effect. Second, the modeled designs are laboratory tested with an impedance tube system. Finally, the practical acoustic absorber design, including framing and mounting methods, is finalized and tested in an ISO accredited reverberation chamber. The results of the modeling, impedance tube testing, and the room testing are all considered. It is seen that the simulation and impedance tube results match very closely, whereas the practical implementation performance is lower in terms of acoustic absorption. This research therefore presents a valuable case study for acoustic absorber designers in helping to better predict the final performance of their designs.
Convention Paper 9158
P11-5 Oscillating Measurement Motion – Myth or Magic?—Wolfgang Heß, Fraunhofer Institute for Integrated Circuits IIS - Erlangen, Germany; Stefan Varga, Fraunhofer Institute for Integrated Circuits IIS - Erlangen, Germany
Acoustical reproduction in cars is different to acoustical reproduction in rooms or other larger environments. This is caused by the size of the car cabin, by surrounding materials as well as non-ideal loudspeaker enclosures, and reproduction positions. In order to achieve a well balanced sound system, for most sound system tuning engineers, acoustical measurements are essential in the process of designing and optimizing an audio system. This paper analyses and describes different methods of measuring the frequency-gain behavior of single or multiple loudspeakers. When measured at a single position, often dips and notches in the form of comb-filters can be observed in the frequency response. This work focuses on practical aspects: In which way is it possible to measure a frequency response that describes the sound at the listening area as correct as possible, how can we reduce comb-filter effects? In which way is a fast and adequate measurement possible? Results showed a significant reduction by movement of the measurement microphone. An evaluation by listening tests showed that frequency response averaging by microphone movements led not only to smoother magnitude responses but also to better sound experience through less equalization.
Convention Paper 9159