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Acoustician Russ Cooper created this presentation to show the science behind the tuning of a hall.

Acoustician Russ Cooper created this presentation to show the science behind the tuning of a hall.

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  • This tells us a great deal about what to expect about how the acoustics will be in a given room
  • ADD OR REPLACE WITH FLORIDA GULF COAST

Skypac acoustic talk Skypac acoustic talk Presentation Transcript

  • ACOUSTICS AND THEPERFORMING ARTS Russ Cooper Jaffe Holden Acoustics Norwalk, CT FEBRUARY 14, 2012
  • ACOUSTICS 101
  • WHAT IS SOUND? ExpansionCompression
  • POINT SOURCE PRESSURE WAVES
  • PRESSURE WAVES FROM TUNING FORK
  • THE HUMAN EAR T T T T TT T T T T T T T
  • EAR DRUM RESPONSE TO PRESSURE WAVES
  • PROPERTIES OF SOUND θ θ θR θ θ θ O θθ θθ θR O P P R θR O P P R90 dB 75 dBθR O P θR O P θR O P
  • SOUND ABSORPTIVE MATERIALS
  • SOUND REFLECTIVE MATERIALS
  • THE SCIENCE OF ACOUSTICS• Wallace Clement Sabine, the father of acoustics uses organ pipes as sound sources and seat cushions in a Harvard University lab in 1898 to measure the properties of sound.• Sabine goes on to assist in the design of Boston Symphony Hall in 1900, considered the best acoustics for a concert hall in the world
  • BOSTON SYMPHONY HALL
  • TYPICAL REVERBERATION TIME DECAY CURVE60 Reverb Time = Volume Sound Absorption Rt60 = V 20 Sα0 0 2
  • ABSORBED - TRANSMITTED - REFLECTED SOUND SOUND % ABSORBED & ABSORPTION MATERIAL % REFLECTED TRANSMITTED COEFFICIENT (α ) Open Window 0 100 1.00 30 70 0.70 Acoustical Ceiling Tile ¾” Plaster On 93 7 0.07 Lath
  • SCIENTIFIC ACOUSTIC TERMS• Reverberation Time: RT60• Early Decay Time: EDT• Clarity: C80• Inter-aural Cross Correlation: IACC• Bass Ratio (Warmth): BR• Direction of Reflection: LF• Initial Time Delay Gap: ITDG• Gain (Loudness): G• Noise Criteria: NC
  • ACOUSTIC DESIGN OFPERFORMANCE HALLS
  • SCIENCE OF ACOUSTICS• We can predict and model how individual sources of sound radiating equally in all directions with equal energy levels at all frequencies will react at a given receiver position in a hall.
  • SCIENCE OF ACOUSTICS• However, most performances involve multiple sources in different locations with varying radiation patterns and different energy levels at different frequencies.
  • SCIENCE OF ACOUSTICSEqual Energy at every Frequency for Acoustic Model Actual Musical Instruments – Varying Energy at Different Frequencies
  • ARTISTIC APPLICATION OF ACOUSTICS• The art is in the application of the science•Experience with how sound should behave on stagein musical ensemble• Acoustic “Listening” – how the room will sound on the stage, in the pit, in the orchestra seats, in the balconies• Intuitive Auralization – The acoustician must “hear” the drawings• Tuning the Hall to achieve the acoustic goals• Interaction of artists with the hall
  • ACOUSTICS FOR MULTI-USE HALLS• Program, program, program• Acoustic Designs: – Proscenium Style – Platform Forward – Concert Hall “Shaper”• Adjustable Acoustic Systems – Draperies, Banners, Panels• Integration of acoustic reflectors, lighting and sound
  • PROSCENIUM STYLE
  • PLATFORM FORWARD
  • CONCERT HALL “SHAPER”
  • SKYPAC ACOUSTIC GOALS1. Classical Music: • Warm, rich, enveloping • Clear & present • Well defined – blended, but distinct • Quiet Room • Excellent on-stage hearing2. Theatre / Dance / Opera: • Dry, but warm • Articulate & intelligible3. Amplified Events: • Not too loud, room won’t “Overload” • No Echoes • Bass Control
  • ACOUSTIC CHALLENGES WITH VARIABLE PROGRAMSMusic andSpeech havedifferentacousticrequirements Speech is Directional
  • ACOUSTIC CHALLENGES WITH VARIABLE PROGRAMSMusic andSpeech havedifferentacousticrequirements Music is Omni-Directional
  • ACOUSTIC SOLUTION FOR MUSIC• Light weight demountable orchestra • Utilizes reverberant stage house shell in a stage house coupling for low frequencies• Uses reflective shell for mid and high frequency sound projection to audience and performers Music: Light Weight Orchestra Shell
  • ADJUSTABLE ACOUSTICS FOR PERFORMANCE SPACESWhen is it needed? – Variable acoustic systems allow hall to have different reverberation times – Can be used to control echoes from loudspeakers – Can be used to “tune” the room for different programs
  • Experience Shows That AcousticsDiffer For Each Type of Performance Preferred Liveness (Rt) Mid-frequency 2.0 2.0 sec. 1.4 1.0 1.0 sec. 0.8 Lecture Drama Opera/Ballet Symphony
  • TYPES OF ADJUSTABLE ACOUSTIC SYSTEMS• Velour Drapes - 25 to 32 ounce material on track or drum or winch line• Hung in space or against a wall• Hidden behind sound transparent material or scrim or exposed• Fiberglass or Felt or wool panels tracked or on drum• Low frequency panel absorbers
  • ACOUSTIC CURTAINS
  • FABRIC COVERED TRACKING PANELS Vertically tracking acoustical panels
  • CONCEALED ADJUSTABLE ACOUSTIC SYSTEMAcoustic banners hiddenbehind perforated metal
  • WOOL BANNERS
  • ADJUSTABLE ACOUSTIC SYSTEMS
  • ADJUSTABLE ACOUSTIC SYSTEMS
  • POPULAR MUSIC ACOUSTIC CHALLENGES ECHO
  • ADJUSTABLE ACOUSTIC SYSTEMS
  • LARGE VOLUME-TO-SEAT RATIO IS ACHARACTERISTIC OF ACOUSTICALLY EXCELLENT HALLS (CUBIC FEET PER PERSON) 400 360 312 305 300 VOLUME/SEAT 300 200 100 0 LL L L HA HA C ON PA IE SS Y EG ST BA SK BO RN CA
  • QUIET NOISE LEVELS ARE A CHARACTERISTIC OF ACOUSTICALLY EXCELLENT HALLS GOOD SKYPAC HALL QUALITY LEVEL POINT OF BETTER DIMINISHING RETURN BEST 25 20 15 10 5 NC- NOISE CRITERIA
  • ADJUSTABLE ACOUSTICAL DRAPES OPTIMIZE SKYPAC REVERBERATION TIME 2.5 ?? 1.6 2.0 REVERBERATION TIME 1.45 1.5 ?? Calculated Measured (SECONDS) 1.3 ?? Calculated Measured 1.0 Measured Calculated 0.5 0 0% 50% 100% PERCENTAGEOF ABSORPTION INTRODUCED INTO HALL
  • CONSTRUCTION ISSUES THAT AFFECT THE ACOUSTICSHoles in walls reduce the sound isolation between spaces
  • Poor installation of acoustic devices
  • No coordination of utility requirements and acoustic requirements
  • ACOUSTICAL TUNING• Listening to the various ensembles to determine the correct setting of the adjustable acoustical systems• Working with the music directors for proper musician placement on stage• Operating all adjustable systems in the hall• Measuring the reverberation time in unoccupied condition• Listening to the ensembles with full audience to confirm settings• Measuring the reverberation time in occupied condition
  • SKYPAC