Page 11 - Winter 2011

IN SEARCH OF A NEW PARADIGM:
HOW DO OUR PARAMETERS AND MEASUREMENT TECHNIQUES CONSTRAIN APPROACHES TO CONCERT HALL DESIGN?
Larry Kirkegaard and Tim Gulsrud
Kirkegaard Associates 801 W. Adams Chicago, Illinois 60607 and
954 Pearl Street Boulder, Colorado 80302
“Our computers can collect terabytes of data at blazing speeds, but those data must be guided by artful listening, with deep conviction that there is much more that we need to learn.”
Introduction
Concert hall design is known to be
part art and part science. While
the development of the science
side of concert hall design has brought
real and significant progress to the field
especially over the last 50 years, the
quest to reduce concert hall acoustics
to a set of parameters has also nar-
rowed our vision and range of enquiry
from what is truly required to achieve
excellent acoustics. In this article we
take a critical view of the current scien-
tific paradigm for concert hall design,
explore some of its shortcomings, and offer suggestions for new ways to approach this complex subject in a more holis- tic and multidisciplinary manner. Real progress in concert hall design will require not only building on the scientific understanding already achieved, but also making closer connections to the art forms being performed there.
The problem is not that scientifically developed parame- ters are incorrect, but that they are insufficient for the task of designing acoustically superior concert halls.
What do the parameters miss?
Acoustics researchers have contributed to the develop- ment of parameters that many acousticians use in their design of concert halls and other performance spaces. While these parameters have been helpful in focusing designers’ attention to important acoustics qualities, rigorous applica- tion of these parameters does not guarantee excellent acoustics.
A wide range of acoustics parameters is found in the lit- erature. A good example is the ISO 3382 international stan-
dard, which includes a helpful summary
of the most widely used parameters in
1
room acoustics. In addition to the clas-
sic reverberation time, this standard divides parameters into other categories including sound strength, early decay time, balance of early and late energy, and early lateral energy. Table 1 below summarizes and describes the subjec- tive definition of these basic room acoustics parameters, along with some other widely used ones.
Notwithstanding the apparent validity of these parameters, we main- tain that they are insufficient. They simply do not address all the acoustical qualities that are critically important to achiev- ing great concert hall acoustics. During our interactions with musicians and other critical listeners in concert halls, we reg-
ularly hear comments such as:
Clarity measurements are in the correct range, but the
sound is muddled and unclear...
The sound is unbearably harsh above a mezzo forte dynamic...
The bass sounds emasculated and lacks impact...
The celli are strong, but I cannot hear the double basses... The core of the tympani sound is missing...
I cannot hear the soloist above the orchestra...
Some instruments sound disembodied, like their sound is coming from the wrong direction...
The balance between winds and strings is not right...
I cannot hear my colleagues across the orchestra...
These of course are just a few examples of the many com- ments we encounter in our consulting practice. But, they illustrate how very real acoustics issues tend not to fit very
Table 1. Summary of frequently used room acoustics parameters
Category
Parameter
Subjective Definition
Room decay time
T30, T60
Lingering of sound when music stops
Early decay time
EDT
Sense of reverberance
Sound strength
G
Loudness
Early/late energy balance
C80, D50, Ts
Clarity, definition, balance between clarity and reverberance
Early lateral energy
LF, IACC
Spatial impression, apparent source width
Onstage hearing
STearly, STlate
Musicians’ hearing of selves and others
In Search of a New Paradigm 7