From: SFPhysics@aol.com
Date: Sat Jan 22 2000 - 10:45:45 PST
From: SFPhysics@aol.com Message-ID: <f.88009a.25bb54d9@aol.com> Date: Sat, 22 Jan 2000 13:45:45 EST Subject: Re: Davies Hall Acoustics
As some of you may know I have a pipe organ business on the side. I have
worked on the Davies Hall Rufatti Fres. pipe organ. It is considered a junk
organ in a barn by those in the profession. Half of what an organ sounds
like is in the acoustics of the room in which it speaks. From the opening
day at Davies the acoustics have been terrible. All the laws of acoustical
phsyics were ignored. Parallel surfaces allowed for "slap echo", there were
objectionable amounts of constructive and destructive interferences in the
tenor C octaves, square corners above the orchestra became corner reflectors,
etc., and a new group of acoustic engineers were brought in to help with the
unacceptable acoustics. They moved walls, removed seats, installed plexiglas
flying saucers so the orchestra could actually hear itself, installed more
moveable drop curtains from the ceiling to absorb sound reflections, etc.,
and there were other small improvements. The organ still sounded like crap
but now you could hear it better! The orchestra still had serious
directionality problems that were frequency (pitch) related. Where you sat
in the hall determined what part of the orchestra you would hear. After
having many seasons of season tickets in various locations, my wife and I
gave up and did not renew our subscription. The problem you describe is from
the corner reflector effect and from the lower pitches which acoustically
couple to the walls. The opposite occurs on the mezzanine level seats where
you see some musicians playing frantically but do not hear a single note of
their efforts.
Why do some of the older halls do so well, e.g.: The late great San
Francisco FOX Theatre? Large parabolic plaster surfaces were located over
the orchestra pit. Even the indirect lighting alcoves with the hand painted
artistic scenes in the ceiling were parabolic. When the sound went up it was
reflected directly back down into the audience. There were no flat or
parallel surfaces in the house. The orchestra pit was at the focus of a
large pie wedge shaped auditorium so sound would radiate outward evenly. In
effect the auditorium had no square corners. The sound was even and so well
propagated that a person on stage of that near 5,000 seat house could talk
unaided by electronics on stage and have every seat hear him or her.
Davies was designed by the new architects who depart from the lessons learned
from the past and figure that the hall can be altered by the electronics
which have been employed in most new halls. This is fine unless you are near
one of the speakers designed to put out cancellation signals and you are not
at the null point. You get blasted. Davies still needs a lot of work to
make it a decent hall fit for San Francsico but, like the emperor's new
cloths, not many are talking about it.
Al Sefl
Acoustics was once a serious part of university Physics........
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