geometrical design studies
DESCRIPTION
GEOMETRICAL DESIGN STUDIES. ACOUSTICS OF CONCERT HALLS AND ROOMS. Handbook of Acoustics, Chapter 9 Long, Architectural Acoustics, Chapter 19. THE LISTENING ENVIRONMENT. • STRONG LATERAL REFLECTIONS SO AUDIENCE FEELS ENVELOPED • A STRONG REVERBERANT FIELD - PowerPoint PPT PresentationTRANSCRIPT
GEOMETRICAL DESIGN STUDIES
ACOUSTICS OF CONCERT HALLS AND ROOMS
Handbook of Acoustics, Chapter 9
Long, Architectural Acoustics, Chapter 19
THE LISTENING ENVIRONMENT
• STRONG LATERAL REFLECTIONS SO AUDIENCE FEELS ENVELOPED
• A STRONG REVERBERANT FIELD
• CLARITY AND DEFINITION FOR RAPID MUSICAL PASSAGES
• ADEQUATE LOUDNESS THROUGHOUT THE HALL
• ROOM MUST NOT COLOR THE NATURAL INSTRUMENT SPECTRA
• LOW BACKGROUND NOISE (NC 20 OR LESS)
•SMOOTH DECAY WITHOUT ECHOES
• PERFORMERS SHOULD BE ABLE TO HEAR EACH OTHER (ENSEMBLE)
HALL SIZE
SEATING CAPACITY PAYS THE RENT
HOWEVER THE “BEST LIKED” CONCERT HALLS HAVE CAPACITIES OF ABOUT 1800-1900 SEATS
“LEAST LIKED” HALLS AVERAGED 2800 SEATS
BASIC ROOM SHAPES
FAN-SHAPED GREEK/ROMAN THEATER
CIRCUS OR ARENA
SIMPLE PLAN FORMS FOR
CONCERT HALLS IN NORMAL AND SURROUND
CONFIGURATIONS
NORMAL SURROUND
DIRECTIONS OF SIDE-WALL REFLECTIONS
DEPENDING ON ROOM
SHAPE
RECTANGULAR FAN-SHAPE
GRAZING INCIDENCE (LESS THAN 5O)
FOR REFLECTION AT A HARD SURFACE, REFLECTED WAVE IS IN PHASE WITH INCIDENT WAVE AND PRODUCES AN INCREASE (OR DECREASE) IN SOUND LEVEL
10-20 dB IN FOR REFLECTION AT A SOFT SURFACE (SUCH AS THE HEADS OF THE AUDIENCE) REFLECTED WAVE IS 180O OUT OF PHASE WITH INCIDENT WAVE AND WAVE INTERFERENCE CAN AMOUNT TO 10--20 dB IN THE 100--800 Hz RANGE (GADE, 2007)
SEATING ARRANGEMENT
GRAZING INCIDENCE ATTENUATES NOT ONLY THE DIRECT SOUND BUT ALSO THE FIRST-ORDER REFLECTIONS FROM THE SIDE WALLS. THIS RESULTS IN WEAKER EARLY REFLECTIONS AND REDUCED CLARITY, INTIMACY and WARMTH IN THE ORCHESTRA SEATS (“STALLS”)
NORMALLY A CLEARANCE OF 8 cm WILL SUFFICE TO AVOID GRAZING-INCIDENCE ATTENUATION, BUT SIGHT LINES WILL STILL BE UNSATISFACTORY (UNLESS SEATS ARE STAGGERED), INCREASING THE CLEARANCE TO 12 cm WILL MAKE BOTH ACOUSTIC AND VISUAL CONDITIONS SATISFACTORY, BUT THIS IMPLIES A STEEPER FLOOR SLOPE.
CALCULATION OF A FLOOR SLOPE WITH CONSTANT CLEARANCE
A CURVED FLOOR SLOPE WITH CONSTANT CLEARANCE MAY PREVENT EXCESS CLEARANCE IN SEATS CLOSE TO THE SOURCE
SECTION OF A HALL WITH A REAR BALCONY AND CONSTANT CLEARANCE. THE RESULT IS AN INCREASED
SLOPE FOR THE ELEVATED BALCONY
FOR SAFETY THE SLOPE SHOULD NOT EXCEED ABOUT 35O
IMPORTANT PARAMETERS FOR MAINTAINING PROPER SOUND IN SEATS OVERHUNG BY BALCONIES
FOR THEATERS, H>2D
FOR CONCERT HALLS H>D
(GADE, 2007)
UNDER BALCONY EARLY DECAY TIME EDT (Barron, 1993)
VOLUME AND CEILING HEIGHT
VOLUME INFLUENCES BOTH REVERBERANCE AND LOUDNESS. FOR HALLS OF HIGH CAPACITY, A LOW VOLUME PER SEAT HELPS PRESERVE ACOUSTICAL ENERGY.
THOSE WHO PREFER THE MODEL OF BOSTON SYMPHONY HALL PREFER AROUND 9 m3 (320 cu ft) PER SEAT. HALLS SUCH AS McDERMOTT AND BIRMINGHAM (WITH OPENABLE REVERBERATION CHAMBERS) ARE AT OR ABOVE 11 m3 (400 cu ft). THESE HALLS INCLUDE A LARGE MOVEABLE REFLECTOR ABOVE THE ORCHESTRA WHICH OFFSETS SOME OF THE EFFECTS OF A HIGH VOLUME (Long, 2006)
VOLUME PER SEAT FOR SEVERAL HALLS (Long)
ECHO ELIPSES DRAWN WITH SOURCE AND RECEIVER POINTS AT THE FOCI, AND THE SUM OF DISTANCES FROM THE FOCI EQUAL DISTANCE BETWEEN FOCI PLUS 17 m. IF A SURFACE OUTSIDE AN ELLIPSE REFLECTS SOUND TO A LISTENER, IT SHOULD BE MADE ABSORBING (Gade, 2007)
RESHAPING OF CEILING PROFILE TO AVOID FOCUSING AND PROVIDE MORE EVEN SOUND
DISTRIBUTION
DIFFUSION BY GEOMETRIC SHAPES:
TRIANGULAR RECTANGULAR
PROTRUSIONS SEMI-CYLINDRICAL
SURFACE
CROSS SECTION OF A PHASE GRATING (QUADRATIC RESIDUE) SOUND DIFFUSER, AS
SUGGESTED BY SCHROEDER (1975)
MAXIMUM DEPTH OF THE WELLS DETERMINES THE LOW-FREQUENCY LIMIT OF THE DIFFUSER. WELL DEPTH SHOULD BE 12 TIMES WAVELENGTH AT THE LOWEST FREQUENCY.THE HIGHEST FREQUENCY IS DETERMINED BY WELL WIDTH, WHICH IS A HALF WAVELENGTH AT THE HIGHEST FREQUENCY.
SYMPHONYHALLBOSTON
V =18,750 m3
39 m x23.6 m x18.6 m
2625 seats
Furthest seat: 40.5 m
T60 = 1.85 s
V/N = 7.14 m3
NEUES GEWANDHAUS
LEIPZIG
CONCERTGEBAUW
AMSTERDAM
BERLIN PHILHARMONIC HALL
CHRISTCHURCH TOWN HALL, NEW ZEALAND BUILT 19722662 seats, V = 20,000m3, T = 2.4s
SEGERSTROM HALL, ORANGE COUNTY
Seats 2900Acoustic Design, Marshall, Hyde, Paoletti
STANFORD MEMORIAL CHURCH