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 France�s 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
