The effects of seating on the acoustics of auditoria

Davies, WJ

Abstract

The two main attributes of seating in auditoria have been investigated. Tle first
is random incidence absorption. The second is the low-frequency selective
attenuation which seating can impart to sound travelling over it at grazing
incidence: the so-called "seat dip" effect.
It was found that there was a need for a more accurate laboratory measurement
method to predict auditorium seat absorption. The traditional method tended to
overpredict the absorption of the exposed front and sides of seating blocks. A new
method was studied which involves the use of barriers to obtain realistic
measurements of front and side absorption. The new method was validated by
comparing measurements of seats made in a reverberation chamber with in-situ
absorption data for the same seats, calculated from reverberation time
measurements in ten auditoria with and without the seats present. The accuracy of
the new method was found to be satisfactory in all cases, although a severe lack of
diffusion in two of the halls hindered the validation process.
The important physical factors affecting seat dip attenuation were investigated by
measurements in a concert hall and on scale model seats. A scheme for reducing
the attenuation with resonant absorbers was evaluated, and a simple theoretical
model developed. 'Ibe subjective significance of the effect was established with a
panel of ten subjects and a fully simulated auditorium sound field. The absolute
threshold of perception of the seat dip effect was found to be 7.1 ± 0.6 dB
attenuation in the 200 Hz octave band of the early field. It was found that seat dip
attenuation might be made less audible in a hall by: (i) supplying early energy along
paths remote from the seating, (ii) increasing the vertical angle of incidence of the
direct sound and (iii) installing resonant absorbers in the floor between seat rows.

Citation

Davies, W. The effects of seating on the acoustics of auditoria. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Aug 18, 2011
• Publicly Available Date: Aug 18, 2011
• Award Date: Jan 1, 1992