Session J Monday, May 14 8:30 - 13:00 hr Room C/D
Room Acoustics & Sound Reinforcement
Chair: Rinus Boone, Technical University Delft, Delft, The Netherlands
8:30 hr J-1
A permanent large scale audio system for sound
reinforcement and zoned announcements was installed in the 760 Hectare (1900
acre) Sydney Olympic Park precinct, the site of 14 major venues for 2000
Olympic Games events. During the Games,
up to 450,000 people were present on the site at any time. Around the site, 550
distributed loudspeakers are driven from 56 adjacent dual channel amplifiers.
Networked digital audio directly accesses loudspeaker amplifiers, carried
across the site on both optic-fiber and copper data links. The paper discusses
benefits of this approach, including flexible signal routing, distributed
signal processing, direct to network digital message play-out and centralized
or local control alternatives.
9:00 hr J-2
The office sound in open spaces can be consequently
designed to obtain confidence and acceptance. The improvement of listening
conditions includes the avoidance of interfering speech from adjacent working
places, disturbing noise from computers or telephones, sound from air conditioning
outlets, or noise from photocopy machines. Sound design is defined as the build
up of a pleasant and well accepted soundfield within the office area. The tools
implemented are absorption, distance and desk orientation combined with
artificial ambient noise for masking purposes. A field of confidence can be
found within limits of acceptance. Beyond these limits, disadvantages occur
with the consequence of negative judgments and rejections. The limits are
sometimes so strong that little adjustments must be made and overcome with
other measures. Some open-planned offices need to be continuously monitored,
checking the important influencing factors. The goal is privacy for every
office working place with different privacy requirements. A scale of privacy exists
and must be used properly.
9:30 hr J-3
The combination of a well-known electro acoustical
simulation software with a state-of-the-art room acoustical simulation engine
merging the advantages of both to form a multi-purpose simulation tool, is
introduced. The new tool is useful for consultants for application in complex
situations in medium sized and large rooms. Advantages of combining a high
quality speaker database and a powerful 3D-CAD interface with a hybrid image
source/ray tracing algorithm including diffuse scattering will be discussed.
Details about the room acoustical model and its limitations as well as the
extended possibilities of the system are the main topics of this paper.
10:00 hr J-4
Modes in small rooms may lead to uneven frequency
responses and extended sound decays at low frequencies. In critical listening
environments this often causes unwanted coloration effects, which can be
detrimental to the sound quality. Choosing an appropriately proportioned room
may reduce the audible effects of modes. This paper details a new methodology
for determining the room dimensions for small critical listening spaces. It is
based on numerical optimization of the room dimensions to achieve the flattest
possible frequency response. The method is contrasted with previous techniques.
10:30 hr J-5
This paper presents a novel method to extract Speech
Transmission Index (STI) from reverberated speech utterances using an
artificial neural network. The convolutions of anechoic speech signals and
simulated impulse responses of rooms of various kinds are used to train the
artificial neural network. A time to frequency domain transformation algorithm
is proposed as the pre-processor. A multi-layered feed forward neural network
trained by back-propagation is adopted. Once trained, the neural network can
accurately estimate Speech Transmission Index from speech signals received by a
microphone in rooms. This approach utilizes a naturalistic sound source,
speech, and hence has potential to facilitate occupied measurement.
11:00 hr J-6
New speaker designs use active phase
shifts to optimize line or plane arrays for better directivity control of the
device. To simulate these new speakers in EASE the phase information of such a
system must be measured and stored. Also, in case that measured data is not
available, EASE will calculate phase data assuming minimum phase behavior. EASE
for Windows saves these sets of complex data and allows to present phase balloons
in a wrapped or unwrapped form. A new cluster routine shows the resulting
balloons of complex arrays in magnitude and phase. Special post processing
allows to examine the phase data in many different ways to distinguish real
physical phase jumps from mathematical ones only caused by phase wraps.
11:30 hr J-7
This paper is a proposal for an extension of the WFS
method towards a new direction in adaptive sound reinforcement systems. The
positions of sound sources may be found using array signal processing
techniques. Analysis of an acoustic field can be performed on a microphone
array using the Direction of Arrival algorithm, which can estimate angle of
arrival of acoustic waves, like tones or speech signals. This paper presents
real time analysis of an acoustic field based on the implementation of DOA
algorithms on the DSP board.
12:00 hr J-8
The paper will describe a series of acoustic measurements
in Finnish concert halls. The measurements were made using the IRMA system
described in another paper offered for presentation at the conference. Both
traditional single channel measurements as well as binaural measurements were
taken in all halls. In some halls, also multidimensional measurements were made
using the special probe also described in the above-mentioned paper. The
measurement results are used in a comparison of the acoustic conditions in
Finnish concert spaces with other spaces.
12:30 hr J-9
Sydney 2000 Olympic Games were held in Australia from
September 15 to October 1, 2000 with more than 10,000 athletes in 300 events.
We have designed the sound systems for 34 venues where included not only indoor
but also outdoor events. Computer Acoustic Simulation software was originally
developed to support designing sound system for each venue. It summarizes to
maintain high quality sound and good intelligibility in case of long distance
transmission even for outdoor venues by using digital technology. Furthermore
sound pressure level (SPL) of each venue was measured during the actual Games.
This paper describes how sound systems for the Sydney 2000 Olympic Games were
designed and performed.