AES London 2010
Poster Session P13

P13 - Room Acoustics, Sound Reinforcement, and Instrumentation

Sunday, May 23, 16:30 — 18:00 (Room C4-Foyer)
P13-1 Adaptive Equalizer for Acoustic Feedback Control—Alexis Favrot, Christof Faller, Illusonic LLC - Lausanne, Switzerland
Acoustic feedback is a recurrent problem in audio applications involving amplified closed loop systems. The goal of the proposed acoustic feedback control algorithm is to adapt an equalizer, applied to the microphone signal, to prevent feedback before the effect of it is noticeable. This is achieved by automatically decreasing the gain of an equalizer at frequencies where feedback likely will occur. The equalization curve is determined using information contained in an adaptively estimated feedback path. A computationally efficient implementation of the proposed algorithm, using short-time Fourier transform, is described.
Convention Paper 8053 (Purchase now)

P13-2 The Meshotron: A Network of Specialized Hardware Units for 3-D Digital Waveguide Mesh Acoustic Model Parallelization—Guilherme Campos, Sara Barros, University of Aveiro - Aveiro, Portugal
This paper presents the project of a computing network—the Meshotron—specifically designed for large-scale parallelization of three-dimensional Digital Waveguide Mesh (3-D DWM) room acoustic models. It discusses the motivation of the project, its advantages, and the architecture envisaged for the application-specific hardware (ASH) units to form the network. The initial stages involve the development of a software prototype based on the rectangular mesh topology, using appropriate hardware simulation tools, and the design and test of FPGA-based scattering units for air and boundary nodes.
Convention Paper 8054 (Purchase now)

P13-3 A Hybrid Approach for Real-Time Room Acoustic Response Simulation—Andrea Primavera, Lorenzo Palestini, Stefania Cecchi, Francesco Piazza, Università Politecnica delle Marche - Ancona, Italy; Marco Moschetti, Korg Italy - Osimo, Italy
Reverberation is a well known effect particularly important for music listening especially for recorded and live music. Generally, there are two approaches for artificial reverberation: the desired signal can be obtained by convolving the input signal with a measured impulse response (IR) or a synthetic one. Taking into account the advantages of both approaches, a hybrid artificial reverberation algorithm is presented. The early reflections are derived from a real IR, truncated considering the calculated mixing time, and the reverberation tail is obtained considering the Moorer‘s structure. The parameters defining this structure are derived from the analyzed IR, using a minimization criteria based on Simultaneous Perturbation Stochastic Approximation (SPSA). The obtained results showed a high-quality reverberator with a low computational load.
Convention Paper 8055 (Purchase now)

P13-4 Sensor Networks for Measurement of Acoustic Parameters of Classrooms—Suthikshn Kumar, PESIT - Bangalore, India
Measurement of acoustic parameters such as signal to noise ratio, reverberation time, and background noise is important in order to optimize classroom configuration and architecture. The classroom learning environment can thus be improved. The lecturers and students find comfort and assurance in knowing that the acoustic parameters of the classroom have been measured and indicate good acoustics. We propose sensor networks for acoustic measurement applications. The sensor network consists of an array of inexpensive sensor nodes which communicate and aggregate the acoustic parameters. The paper presents the sensor node architecture and illustrates the typical usage of the sensor networks for the measurement of acoustic parameters in classrooms. This paper will not be presented at the Convention.
Convention Paper 8056 (Purchase now)

P13-5 In Situ Directivity Measurement of Flush-Mounted Loudspeakers in a Non-Environment Listening Room—Daniel Fernández-Comesaña, Paúl Rodriguez-Garcia, Institute of Sound and Vibration Research (ISVR) - Southampton, UK; Soledad Torres-Guijarro, Laboratorio Oficial de Metroloxía de Galicia (LOMG) - Tecnópole Ourense, Spain; Antonio Pena, ETSE Telecomunicación, Universidade de Vigo - Vigo, Spain
Directivity is one important parameter to define the behavior of a loudspeaker. There are many techniques and standards about directivity measurements in anechoic chambers, but in situ measurements of flush-mounted loudspeakers show some specific problems. This paper develops a procedure to measure directivity under the special conditions of a non-environment listening room, introducing the techniques utilized, the problems found with the proposed solutions, and discussing the limitations of the process. The existence of reflections, baffling effects due to adjacent walls and a comparison to theoretical models of the radiation of a piston are discussed.
Convention Paper 8057 (Purchase now)

P13-6 Measurement of Loudspeakers without Using an Anechoic Chamber Utilizing Pulse-Train Measurement Method—Teruo Muraoka, Takahiro Miura, The University of Tokyo - Tokyo, Japan; Haruhito Shimura, Hiroshi Akino, Audio-Technica Corporation - Machida, Japan; Tohru Ifukube, The University of Tokyo - Tokyo, Japan
Generally, loudspeakers are measured in an anechoic chamber. However, those chambers are very expensive, which makes the sound engineer's easy acoustical measurements almost impossible. Thus the authors devised a new measurement without using any anechoic chamber. Traditionally, loudspeakers are measured in an anechoic chamber by installing in a proper speaker enclosure and by driving with swept sinusoidal wave. Loudspeaker's radiated sound is detected with an omnidirectional reference microphone, and the output of the microphone is displayed graphically. If a shotgun microphone is employed instead of omnidirectional microphone, an anechoic chamber will become unnecessary. Furthermore, if pulse-train is used as a test signal, noise in surrounding circumstances will be reduced by applying a synchronous-averaging algorithm. Based upon this idea, the authors measured loudspeaker in any acoustical circumstances and obtained very similar data with that by the traditional method.
Convention Paper 8058 (Purchase now)

P13-7 Acoustic Space Sampling and the Grand Piano in a Non-Anechoic Environment: A Recordist-Centric Approach to the Musical Acoustic Study—Grzegorz Sikora, Brett Leonard, Martha de Francisco, McGill University - Montreal, Quebec, Canada, Centre for Interdisciplinary Research in Music Media and Technology, Montreal, Quebec, Canada; Douglas Eck, Centre for Interdisciplinary Research in Music Media and Technology - Montreal, Quebec, Canada, Université de Montréal, Montreal, Quebec, Canada, International Laboratory for Brain, Music, and Sound Research, Montreal, Quebec, Canada
A novel approach to instrument acoustics research is presented in which the instrument is coupled with a room and both are measured as a single acoustical system, in juxtaposition to many anechoic and computer simulated studies of musical acoustics. The technique is applied to the ubiquitous concert grand piano, where spectral information is gathered through the process of “acoustic space sampling” (AcSS), using more than 1,330 microphones. The physical data is then combined with psychoacoustic predictors to generate a map of timbre. This map is compared to the preference of expert listeners, thereby correlating the physical measures obtained through acoustic space sampling to the application of the recording engineer.
Convention Paper 8059 (Purchase now)