Day 3 – Architectural Acoustics II
Acoustical Evaluation Of Berwick Preschool.
An investigation was made of the
acoustical environment in the Berwick Preschool, Vancouver, in response to
complaints by the teachers. Reverberation times (RTs), background noise levels
(BNL), and in-class sound levels (Lp) were measured
for acoustical evaluation both in the classroom. With respect to the measured RT
and BNL, none of the classrooms in the preschool were acceptable according to
the criteria relevant to this study. A questionnaire was administered to the
Preschool teachers to assess their subjective responses to the acoustical and
non-acoustical environments of the classrooms. Teachers agreed that the
non-acoustical environments in the classrooms were fair, but that the
acoustical environment had problems. In order to improve the acoustical
environments, eight different classroom configurations were simulated using the
CATT room acoustical simulation program. When the surface absorption was
increased, both the RT and speech levels decreased. High absorption was not
effective when the classroom was occupied. RASTI was dependent on the volumes
of the classrooms when the background noise levels were high; however it
depended on the total absorption of the classrooms when the background noise
levels were low. Ceiling heights are critical as well.
Class Talk System For Predicting, And Auralizing Speech In Noise In Classrooms
Murray Hodgson, School of Occupational and Environmental
Hygiene and Department of Mechanical Engineering, University of British
Columbia, 3rd Floor, 2206 East Mall, Vancouver, BC V6T 1Z3, Canada
This paper
discusses the development of the Class Talk system for predicting,
visualizing and auralizing classroom speech in noise. Empirical models used to predict speech and
noise levels, and RTs, are presented.
Male or female speech sources, and overhead, slide or LCD projectors, or
ventilation-noise sources, can have four output levels. Class Talk visualizes the floor-plan,
speech- and noise-source positions, and receiver position. The user can ‘walk through’ the room at will.
In real time, five quantities - background noise level, speech level,
signal-to-noise difference, STI and speech
intelligibility - are displayed, along with occupied and unoccupied
reverberation times. Technical issues
related to the development of the sound module, which will auralize speech in
noise with reverberation, are discussed.
Experimental
Validation Of Plant Noise Empirical Prediction
Models
Murray
Hodgson, School of Occupational and Environmental Hygiene and Department
of Mechanical Engineering, University of British Columbia, 3rd
Floor, 2206 East Mall, Vancouver, BC V6T 1Z3, Canada
The Plant
Noise system predicts noise levels and reverberation times in typical
industrial workrooms from values of the input prediction parameters. The objective of this paper was to evaluate
the empirical models experimentally.
Noise levels and reverberation times were measured in octave bands from
125-400 Hz in a number of different 'typical' workrooms without and with
sound-absorbing ceiling and wall treatments.
These were compared with predicted results to evaluate the models. For treated workrooms, treatment absorption
coefficients were estimated. In the case
of the fitting densities, which are not known a-priori, predictions were made
for a range of values. Values which gave
a best fit with prediction were thus determined and were generalized into an
empirical fitting-density prediction method.
Information was also obtained on how to make accurate predictions in the
case of workrooms with non-flat, inhomogeneous roofs.