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Session B Saturday, May 12 9:30 - 13:00 hr Room C/D

Instrumentation and Measurement

Chair: Menno van der Veen, Ir.Buro Vanderveen, Zwolle, The Netherlands
9:30 hr B-1
The Sound Design System
Shokichiro Hino
Etani Electronics, Tokyo, Japan

The system combines a sound field measurement system and a convolution processing unit with a computer as the central controlling unit. The sound design tool enables equalizers to be generated by directly editing the measured frequency characteristics as seen on the graph. The resulting sound is immediately convoluted for comparative listening tests. An application example of the system adopted for the acoustic design of cars is illustrated.
Paper 5288

10:00 hr B-2
Sound Power: The Forgotten Loudspeaker & Sound System
Peter Mapp
Peter Mapp Associates, Colchester, UK

The Sound Power radiation characteristic of a loudspeaker is shown to be an essential but forgotten parameter in sound system design and loudspeaker characterization. A study has been made of the Sound Power radiation characteristics of a wide range of devices. Data is presented which suggests that in most commercial/industrial and professional applications, it is the sound power response that dominates the situation. The parameter is shown to directly relate to speech intelligibility and it is concluded that this useful parameter should be included in manufacturers data sheets and information.
Printed Paper not available

10:30 hr B-3
A System for Multi-Channel and Binaural Room Response Measurements
Tapio Lokki (1), Matti Karjalainen (1), Timo Peltonen (2), Benoit Gouatarbes (1) & Juha Merimaa (1)
(1) Helsinki University of Technology, Espoo, Finland
(2) Akukon Consulting Engineers, Helsinki, Finland

The development of a system for room acoustical measurements and analysis is described. The goal of the project was a versatile system for multi-channel and binaural investigations of room and concert hall acoustics. It consists of a portable PC-based workstation with multi-channel AD/DA data acquisition, an omnidirectional sound source, a 3-D microphone grid for directional response registration, a dummy head, standard omnidirectional and cardioid microphones, and MLS-based response computation. In addition to traditional room-acoustical attribute analysis, special algorithms have been developed to investigate the time-frequency behavior of responses in different directions, for example in concert halls. Analysis cases of interesting hall measurements are discussed.
Paper 5289

11:00 hr B-4
Estimation of Modal Decay Parameters from Noisy Response Measurements
Matti Karjalainen (1), Vesa V”lim”ki (1), Timo Peltonen (2), Aki M”kivirta (3) & Poju Antsalo (1)
Helsinki University of Technology, Espoo, Finland
Akukon Consulting Engineers, Helsinki, Finland
  Genelec, Iisalmi, Finland

Estimation of modal decay parameters from noisy measurements of reverberant and resonating systems is a common problem in audio and acoustics, e.g., in room and concert hall measurements or musical instrument modeling. In this paper, reliable methods to estimate the initial response level, decay rate, and noise floor level from noisy measurement data are studied and compared. A new method, based on nonlinear optimization of a model for exponential decay plus stationary noise floor, is presented. Comparison with traditional decay parameter estimation techniques using simulated measurement data shows that the proposed method outperforms in accuracy and robustness, especially in extreme SNR conditions. Three cases of practical applications of the method are demonstrated.
Paper 5290

11:30 hr B-5
Quality Evaluation in Broadcasting with Tocade Audio Monitor
Matthieu Latour
Consultant, Ile de France, France

The use of data reduction codecs and sound processors in broadcast does not allow traditional quality measurement methods such as THD, signal-to-noise ratio. In order to find an efficient and cost effective quality evaluation method, Radio Franceís Value Department experimented a tool called Tocade Audio Monitor (from CCETT research center). This device indicates the sound quality of a signal without any reference. It was tested with a CD that gives an image of Radio France programs (music, speech, location reports...). This CD test was used as a reference. All kinds of signal paths were simulated using actual sound processors and data rate reduction codecs encountered at Radio France.
Paper 5291

12:00 hr B-6
A Low Cost Intensity Probe
Ron Raangs, Erik Druyvesteyn & Hans-Elias de Bree
Technical University Enschede, Enschede The Netherlands

Sound Intensity is a useful measure in acoustics because in a reverberant environment free-field measurements can be done. The proposed low cost intensity probe combines a sound particle velocity sensor and a microphone, which can be used as separate devices or in one package. For the latter case the velocity and the pressure are measured at almost the same location. Since the intensity is calculated from the cross-correlation of the velocity and pressure, a very accurate phase matching, as for the p-p method, is not necessary; and its signal-to-noise ratio (SNR) is higher than for the separate sensors. The data-acquisition and processing is implemented on a standard personal computer, combined with a simple calibration, and thus creating a very powerful intensity measuring device.
Paper 5292

12:30 hr B-7
Health Impairing Aspects by Headphones Electro-Magnetic Fields
Florian Koenig
Ultrasone, Penzberg, Germany

Epidemiological studies about extremely-low-frequency electro-magnetic fields underlined human health impairing aspects. This work demonstrates multiply used headphones/headsets as not only near field sound reinforcing devices. Measurements of about 100 different headphones/headsets using Pink Noise at 70 dBSPL(C) reveal that the majority of objects produce a critical (see TCO`95) magnetic flux. Furthermore is illustrated a technique to reduce the head-related magnetic field emissions.
Paper 5293


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