Page 34 - Spring 2019
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Art Hf Cuncert Hall Acuuatica t . '
I‘ 1

dynamics, the spectrum also changes; at higher levels, more It J .,«v;_ ’ r .
overtones are present. These nonlinear radiation characteris- , It 5 . _ ‘g V. t. ‘ '
tics are not represented by an omnidirectional sound source, ! tttl ' - __ __v--. A   E ‘E t .
and the directivity of the sound source has a significant i.rn- l‘ ,"‘",.'“,-¢- | T —
pact on perception of room acoustics (Hochgraf et al., 2017). i _ I!’
This problem becomes more pronounced, complicated, and t, m,,__ A .
perceptually important when considering the radiation of an 

entire orchestra.

In the audience, the listener hears the orchestra spatially, not

rrr°rre“ra11Y- Birreurel and directional Parameters for SPetie1 Figure 3. Boston Symphnny Hall. Phntn by Peter Vamierwarker.
impression are helpful, but measurement of these param-  
eters can be unreliable due to the impacts of microphone V

calibration and orientation on the parametric calculation. —— —- ' "v 7 ‘ , V.’ l '

In addition to directivity mismatches between real sources g ‘

and receivers and those used to measure impulse responses, J/1 G

the frequency ranges of human hearing and radiation from

musical instruments are both significantly larger than the ca-

pabilities of most loudspeakers used for room acoustics mea- it  .

surements. Beyond the inherent limitations of the standard ' fl '

parameters, impulse responses are often measured in unoc-  a

cupied rooms and averaged across multiple seats. Occupied

rooms, however, are significantly different acoustically from ' ‘ '

unoccupied rooms, and acoustical conditions vary signifi-

cantly bgtwgen different seatst Figurz 4. Philharmanie de Paris. Phntn b}/Inmlh Sucks.

As the significance of these li.rnitations has become clearer,

acousticians have developed new ways of analyzing impulse

responses to obtain useful information. More emphasis is Haw DO  Goals and _

being placed on visual and aural inspection of the impulse paramatnc crll-’arla_I"f°r"l_ Deals"? _
response instead of on parameters that can obscure i.rnpor- The follll of l concert hall ls_ clelelmlllell l_)y a vallely of
tant acoustical details. Acousticians also modify standard pa- factors‘ ll-lcllllllllg‘ but l-lol ll'l-l-lll?d_ l°_‘ acousllm Ol-le_ llll llle
“meters in a Variety of ways, including Changing temporal greatest challenges and responsibilities of an acoustician is
increments, separating calculation for early and late parts of lo eclllcale llle lleslgl-l lealll olllle l'l-l-lpllC_all°lls ofloolll shape
the impulse response, and averaging over different frequency a_l-lll slze’ wlllcll lllll-lllammllllly llelellllllle llll? ling: of Pos-
rangest Although these adaptations may help an individual sible acoustical outcomes, so that design decisions are well-
acoustician make sense of data, it makes it diflicult to com- lllllolll-led and Collslslel-ll Wllll llle Perceptual goals‘

pare halls with each other—one of the primary reasons for Case Studies uf Two Camcert Halls:

documenting parameters in the first place. The Influence ufShupe, Size, and Parametric Criteria

New parameters are also emerging, including Griesingers Bolton _Syl-l-lpllolly l-lall _(Flgll" 3) and llle Pllllllalmollle de
(2011) localization metric (LOC) for predicting the ability of Falls (Flgllfl 4) were lllllll over ll Celllllly aparl’ and allllollgll
a listener to detect the position of a sound source and Bassu- llley are used llll llle same Purpose’ they are lllll-lllammllllly
et’s (2011) ratios between low/high (LH) and front/rear (FR) lllllelel-ll acousllcally

lateral energy arriving at the sides of a listeners head. The Constructed in 1900, the shoebox shape of Boston Sym-
potential utility of objective metrics that correlate well with phony Hall is the result of architectural evolution from royal
perception is undeniable, but as more parameters emerge courts, ballrooms, and the successful, similarly shaped Ge-
and their application among acousticians diverges, we are wandhaus Hall in Leipzig, Germany (Beranek, 2004). It was
continually faced by the question of whether parameters fun- the first hall built with any quantitative acoustical design in-
darnentally support or suppress excellent design. put, courtesy of Wallace Clement Sabine and his ti.rnely dis-
a2 1 AI:uuII:I:I Tbday 1 Spring 2019

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