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GEOMETRICAL DESIGN STUDIES ACOUSTICS OF CONCERT HALLS AND ROOMS Handbook of Acoustics, Chapter 9 Long, Architectural Acoustics, Chapter 19

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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 Presentation

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Page 1: GEOMETRICAL  DESIGN STUDIES

GEOMETRICAL DESIGN STUDIES

ACOUSTICS OF CONCERT HALLS AND ROOMS

Handbook of Acoustics, Chapter 9

Long, Architectural Acoustics, Chapter 19

Page 2: GEOMETRICAL  DESIGN STUDIES

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)

Page 3: GEOMETRICAL  DESIGN STUDIES

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

Page 4: GEOMETRICAL  DESIGN STUDIES

BASIC ROOM SHAPES

FAN-SHAPED GREEK/ROMAN THEATER

CIRCUS OR ARENA

Page 5: GEOMETRICAL  DESIGN STUDIES

SIMPLE PLAN FORMS FOR

CONCERT HALLS IN NORMAL AND SURROUND

CONFIGURATIONS

NORMAL SURROUND

Page 6: GEOMETRICAL  DESIGN STUDIES

DIRECTIONS OF SIDE-WALL REFLECTIONS

DEPENDING ON ROOM

SHAPE

RECTANGULAR FAN-SHAPE

Page 7: GEOMETRICAL  DESIGN STUDIES

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)

Page 8: GEOMETRICAL  DESIGN STUDIES

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.

Page 9: GEOMETRICAL  DESIGN STUDIES

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

Page 10: GEOMETRICAL  DESIGN STUDIES

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

Page 11: GEOMETRICAL  DESIGN STUDIES

IMPORTANT PARAMETERS FOR MAINTAINING PROPER SOUND IN SEATS OVERHUNG BY BALCONIES

FOR THEATERS, H>2D

FOR CONCERT HALLS H>D

(GADE, 2007)

Page 12: GEOMETRICAL  DESIGN STUDIES

UNDER BALCONY EARLY DECAY TIME EDT (Barron, 1993)

Page 13: GEOMETRICAL  DESIGN STUDIES

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)

Page 14: GEOMETRICAL  DESIGN STUDIES

VOLUME PER SEAT FOR SEVERAL HALLS (Long)

Page 15: GEOMETRICAL  DESIGN STUDIES

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)

Page 16: GEOMETRICAL  DESIGN STUDIES

RESHAPING OF CEILING PROFILE TO AVOID FOCUSING AND PROVIDE MORE EVEN SOUND

DISTRIBUTION

Page 17: GEOMETRICAL  DESIGN STUDIES

DIFFUSION BY GEOMETRIC SHAPES:

TRIANGULAR RECTANGULAR

PROTRUSIONS SEMI-CYLINDRICAL

SURFACE

Page 18: GEOMETRICAL  DESIGN STUDIES

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.

Page 19: GEOMETRICAL  DESIGN STUDIES

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

Page 20: GEOMETRICAL  DESIGN STUDIES

NEUES GEWANDHAUS

LEIPZIG

Page 22: GEOMETRICAL  DESIGN STUDIES

BERLIN PHILHARMONIC HALL

Page 23: GEOMETRICAL  DESIGN STUDIES

CHRISTCHURCH TOWN HALL, NEW ZEALAND BUILT 19722662 seats, V = 20,000m3, T = 2.4s

Page 24: GEOMETRICAL  DESIGN STUDIES

SEGERSTROM HALL, ORANGE COUNTY

Seats 2900Acoustic Design, Marshall, Hyde, Paoletti

Page 25: GEOMETRICAL  DESIGN STUDIES

STANFORD MEMORIAL CHURCH