Arch 2440–entech Ii: Exam Two Acoustics Guide

Transcript

ARCH 2440–ENTECH II: Exam Two Acoustics Guide READINGS FROM EGAN, PP. 2-80; 117-286; & 320-378. TERMINOLOGY • KNOW THE FOLLOWING TERMS FROM OUTLINE #10: O NOISE  UNDESIRABLE OR OBJECTIONABLE SOUND. O PITCH  SUBJECTIVE HUMAN RESPONSE OF HUMAN HEARING TO FREQUENCY. O FREQUENCY  THE RATE OF REPETITION OF A PERIODIC EVENT; THE RATE OF OSCILLATION OF MOLECULES. O TONE  A SOUND OF ONLY A SINGLE FREQUENCY. • KNOW THE FOLLOWING TERMS FROM OUTLINE #11: O CLARITY.  THE ABILITY TO PERCEIVE MUSICAL DETAIL.  RANGE FROM CLEAR TO BLURRED. O REVERBERANCE.  THE PERSISTENCE OF SOUND AT MID-FREQUENCIES.  RANGE FROM LIVE TO DEAD. O WARMTH.  THE LIVENESS OF BASS COMPARED TO MID- AND TREBLE FREQUENCIES.  RANGE FROM WARM BASS TO COLD BASS  BASS 20% MORE THAN TREBBLE O INTIMACY.  THE DEGREE OF IDENTIFICATION WITH THE PERFORMANCE.  RANGE FROM INTIMATE SOUND TO REMOTE SOUND. O ENVELOPMENT  THE SPATIAL ASPECT OF PERCEIVED MUSIC; THE DEGREE TO WHICH ONE FEELS SURROUNDED BY THE SOUND.  RANGE FROM RICH DIFFUSION TO POOR DIFFUSION. O ECHOES  LONG-DELAYED SOUND REFLECTIONS THAT ARE CLEARLY HEARD  60 FEET O ARTICULATION INDEX  SUBJECTIVE MEASURE OF SPEECH INTELLIGIBILITY CALCULATED FROM THE SCORES OF A GROUP OF EXPERIENCED LISTENERS WITH NORMAL HEARING WHO WRITE SENTENCES, WORDS, OR SYLLABLES READ TO THEM FROM SELECTED LISTS.  VARIES WITH LOCATION • KNOW THE FOLLOWING TERMS FROM OUTLINE #12: O SOUND ABSORPTION COEFFICIENT  DESCRIBES THE FRACTION OF THE INCIDENT SOUND ENERGY THAT A MATERIAL ABSORBS. THEORETICALLY IT CAN VARY FROM 0 (NO SOUND ENERGY ABSORBED) TO 1.0 (PERFECT ABSORPTION OF ALL INCIDENT SOUND ENERGY) O NOISE REDUCTION COEFFICIENT  THE ARITHMATIC AVERAGE OF THE SOUND ABSORPTION COEFFIECIENTS AT 250, 500, 1000, AND 2000HZ FOR A SPECIFIC MATERIAL AND MOUNTING CONDITION. THE NRC IS INTENDED AS A SINGLE NUMBER RATING OF SOUND ABSORBING EFFICIENCY AT MID FREQUENCIES. O SABINS  A UNIT OF ACOUSTIC ABSORPTION EQUIVALENT TO THE ABSORPTION BY A SQUARE FOOT OF A SURFACE THAT ABSORBS ALL INCIDENT SOUND  THE NUMBER OF SABINES=SURFACE AREA X THE ABSORPTION COEFFICIENT O FLUTTER ECHO  REPEATED ECHOES TRAVERSING BACK AND FORTH BETWEEN TWO PARALLEL SURFACES.  REQUIRES AN IMPULSE SOURCE.  PERCEIVED AS A BUZZING OR CLICKING SOUND. O ROOM RESONANCE  SIMILAR TO FLUTTER IN PRINCIPLE BUT CAUSED BY PURE TONE SOURCES.  PERCEIVED AS VARIATIONS IN SOUND LEVEL. O FOCUSING  CAUSED BY CONCAVE SURFACES  REFLECTED SOUND IS CONCENTRATED INTO CERTAIN AREAS.  CREATES HOT AND DEAD SPOTS ACOUSTICALLY. O CREEP  REFLECTION OF SOUND ALONG A CURVED SURFACE FROM A SOURCE NEAR THE SURFACE.  ALTHOUGH THE SOUND CAN BE HEARD AT POINTS ALONG THE SURFACE, IT IS INAUDIBLE AWAY FROM THE SURFACE. O DIFFRACTION  THE BENDING OR FLOWING OF A SOUND WAVE AROUND AN OBJECT OR THROUGH AN OPENING.   2  IMPINGING SOUND WAVES WILL READILY DIFFRACT AROUND PANELS THAT ARE SMALLER THAN THEIR WAVELENGTH. O REVERBERATION TIME  THE PERSISTENCE OF SOUND AT MID-FREQUENCIES.  DETERMINED BY ROOM VOLUME AND TOTAL ABSORPTION AT THAT FREQUENCY. • KNOW THE FOLLOWING TERMS FROM OUTLINE #13: O REALISM (DIRECTIVITY)  CHARACTERISTIC WHEREBY THE SOUND APPEARS TO BE COMING FROM THE ORIGINATING SOURCE.  HUMAN EAR DIFFERENTIATES SOUND BETTER IN THE HORIZONTAL PLANE THAN THE VERTICAL PLANE. (SPEAKER PLACEMENT) O INTELLIGIBILITY  REVERBERATION: 17MS DELAY OR LESS FOR SPEECH.  GOOD ARTICULATION INDEX. (0.7 OR BETTER) O QUALITY  FREQUENCY RESPONSE FREE FROM DISTORTION (NOT TINNY OR BOOMY). O WOOFER  LOW-FREQUENCY LOUDSPEAKERS IN A LARGE CABINET ENCLOSURE. O TWEETER  HIGH-FREQUENCY HORNS WITH A FLARED SHAPE TO GIVE DIRECTION TO SHORTER WAVELENGTHS. O **WHICH OF THE FOLLOWING LOAD SPEAKERS HAS BEST REALISM: CENTRAL CLUSTER ; (SEAT WORST) • KNOW THE FOLLOWING TERMS FROM OUTLINE #14 O TRANSMISSION LOSS  THE RATIO, EXPRESSED IN DECIBELS, OF THE ACOUSTIC ENERGY RERADIATED BY A BARRIER TO THE ACOUSTIC ENERGY INCIDENT ON IT.  THE DIFFERENCE IN SOUND PRESSURE LEVEL BETWEEN THE INCIDENT SIDE & THE OPPOSITE SIDE OF THE CONSTRUCTION.  OBTAINED FROM LABORATORY TESTS. O NOISE REDUCTION  THE DIFFERENCE BETWEEN THE INTENSITY LEVEL IN TWO ACTUAL ROOMS. O SOUND TRANSMISSION CLASS  COMMONLY USED INDEX FOR EVALUATING A BUILDING CONSTRUCTION FOR ITS PERFORMANCE IN BLOCKING AIRBORNE SOUND TRANSMISSION.  SINGLE NUMBER INDEX RANGING FROM 0 (NO BLOCKING) TO 80 (VIRTUALLY NO SOUND TRANSFER).    STC 30: YOU CAN HEAR NORMAL CONVERSATION WITHOUT MUCH TROUBLE.  STC 60: HIGH-POWERED SHOUTING MATCH WOULD BE A MERE RUMBLE. 3 O FLANKING  REFERS TO SOUND ENERGY BYPASSING CONSTRUCTION THROUGH INDIRECT PATHS. O IMPACT ISOLATION CLASS  A SINGLE-NUMBER RATING OF THE IMPACT SOUND PERFORMANCE OF A FLOORCEILING CONSTRUCTION TESTED OVER A STANDARD FREQUENCY RANGE.  THE HIGHER THE IMPACT ISOLATION CLASS, THE MORE EFFICIENT THE CONSTRUCTION WILL BE IN REDUCING IMPACT SOUND TRANSMISSION.  DOES NOT TEST BELOW 100 O DAMPING & ISOLATION  DAMPING.  THE RIGID COUPLING OF THE VIBRATING SOURCE TO A LARGE MASS (FREQUENTLY CALLED AN INERTIA BLOCK).  MUCH OF THE ENERGY IS ABSORBED AND DISSIPATED AS FRICTION, THE REMAINDER RESULTS IN LOWER-AMPLITUDE VIBRATION.  ISOLATION.  SUPPORTING THE VIBRATING MASS OR ELEMENT ON RESILIENT SUPPORTS.  THE EQUIPMENT CONTINUES TO BE A SOURCE OF AIRBORNE SOUND & VIBRATIONS, BUT THE FEELABLE VIBRATIONS IN THE STRUCTURE AND THE STRUCTURE-BORNE SOUND WILL BE CONSIDERABLY REDUCED. • KNOW THE FOLLOWING TERMS FROM OUTLINE #15: O KEYNOTE SOUNDS  THOSE SOUNDS WHICH ARE HEARD BY A PARTICULAR SOCIETY CONTINUOUSLY OR FREQUENTLY ENOUGH TO FORM A BACKGROUND AGAINST WHICH OTHER SOUNDS ARE HEARD.  NORTHERN HINTERLAND: •  PRAIRIES: •  THE SOUNDS OF ICE AND SNOW BECOME KEYNOTE SOUNDS. THE SOUND OF THE WIND BECOMES A KEYNOTE SOUND. ELECTRONIC CULTURES: • TRANSFORMER HUM. • IN AMERICA PEOPLE TEND TO HUM IN B NATURAL WHICH IS ABOUT THE SAME FREQUENCY AS ALTERNATING CURRENT (60 CYCLES PER SECOND). • IN EUROPE PEOPLE HUM IN G SHARP WHICH IS ABOUT THE SAME AS EUROPEAN ELECTRICAL CURRENT (50 CYCLES PER SECOND) O SIGNALS  FOREGROUND SOUNDS (LISTENED TO CONSCIOUSLY), GENERALLY THESE SOUNDS ARE LISTENED TO BECAUSE THEY GIVE SOME FORM OF ACOUSTIC WARNING.    EXAMPLES: BELLS, WHISTLES, HORNS & SIRENS. 4 O SOUNDMARKS  THE TERM IS DERIVED FROM LANDMARK, & REFERS TO A COMMUNITY SOUND THAT IS UNIQUE OR POSSESSES QUALITIES WHICH MAKE IT SPECIALLY REGARDED OR NOTICED BY THE PEOPLE IN THAT COMMUNITY. CALCULATIONS • KNOW HOW TO DO THE FOLLOWING: O ADD DECIBELS USING THE RULE OF THUMB METHOD SHOWN IN YOUR TEXTBOOK (EGAN PP. 23-24). WHEN TWO DB VALUES DIFFER BY ADD THE FOLLOWING DB TO THE HIGHER VALUE 0 OR 1 3 2 OR 3 2 4 TO 8 1 9 OR MORE 0 >>> WHEN SEVERAL DB VALUES ARE TO BE ADDED, ADD TWO AT A TIME <<< O KNOW HOW TO DETERMINE THE DROP IN SOUND MAGNITUDE AS THE DISTANCE FROM THE SOURCE INCREASES USING THE RULE OF THUMB METHOD SHOW IN CLASS.  A RULE OF THUMB FOR CHECKING SOUND PROPAGATION CALCULATION IS THAT EVERY TIME THE DISTANCE FROM THE SOURCE DOUBLES THE SOUND INTENSITY LEVEL DECREASES BY SIX DECIBELS. O CALCULATION REVERBERATION TIME.  REVERBERATION TIME = (0.05 X ROOM VOLUME) / (TOTAL # OF SABINES)  THE NUMBER OF SABINES =SURFACE AREA X THE ABSORPTION COEFFICIENT O ADDING A NUMBER OF IDENTICAL SOURCES.  SILTOTAL (DB) = SILSOURCE (DB) + 10LOG(#SOURCES) O NOISE REDUCTION THROUGH A WALL.  NR = TL (STC RATING) + 10LOG(AR (SABINES)/SA) HISTORY • KNOW THE FOLLOWING: O THE CONTRIBUTIONS OF LORD RAYLEIGH AND WALACE SABINE.  LORD RAYLEIGH (1842-1919):  “THEORY OF SOUND” (1877).  PUT TOGETHER MATERIAL SCATTERED IN LEARNED JOURNALS INTO AN AUTHORITATIVE REFERENCE WHICH WAS TO BE THE DEFINITIVE TREATISE FOR MANY YEARS.  WALLACE SABINE (1868-1919):  FATHER OF MODERN ARCHITECTURAL ACOUSTICS.  LAW CONNECTING REVERBERATION TIME WITH ROOM VOLUME AND THE AMOUNT OF SOUND ABSORBING MATERIAL.    BOSTON’S SYMPHONY HALL (1898). 5 O THE ACOUSTICAL PROPERTIES OF GREEK THEATERS, GOTHIC CATHEDRALS, RENAISSANCE & BAROQUE THEATERS AND OPERA HOUSES, AND ROCOCCO TOWNHOUSES.  GREEK THEATERS:  ACOUSTICALLY SHELTERED HILLSIDE LOCATIONS.  IMPROVEMENTS IN THE DIRECT SOUND PATH.  SEMI-CIRCULAR PLAN FORM.  RAKED SEATING.  STAGE RAISED & OF A MODEST DIMENSION.  TYPICALLY SET IN A NATURAL DISHING OF GROUND PROVIDING A NATURAL RAKING OF SEATING & AN ACOUSTICAL BUFFER.  MEDIEVAL CATHEDRALS:  ACOUSTICAL CHARACTERISTICS: • LARGE ROOM VOLUMES. • HIGHLY REFLECTIVE SURFACES. • LONG REVERBERATION TIMES (ABOUT EIGHT SECONDS). • TRADITIONS OF ORGAN MUSIC, INCANTATION & RECITAL DEVELOPED AROUND THE ACOUSTICS OF THE SPACE. •  BELL TOWERS. CATHEDRALS:  EVOLUTION OF FORMS TOWARD HIGHER STRUCTURES (4 TO 1 HEIGHT TO WIDTH RATIO).  REINFORCED THE REFLECTED SOUND DOWN FROM THE VAULTS STRESSING THE TIME DELAY.  ENGENDERED A SPECIAL TRADITION OF ORGAN MUSIC, INCANTATION & RECITAL.  LARGE CHURCHES TENDED TO HAVE A SYMPATHETIC TONE SOMEWHERE NEAR A OF A FLAT, SO THAT IF THE PRIEST RECITED IN THIS TONE THE SONOROUS LATIN VOWELS WOULD BOOM.   BELL TOWERS: • THE AREA REACHED BY A BELL TOWER DEFINE THE PARISH. • SOMETIMES AS GREAT AS A TEN MILE RADIUS. RENAISSANCE THEATERS & BAROQUE OPERA HOUSES:  REVIVAL OF ROMAN THEATER FORM. • FULL ENCLOSURE OF THE AUDITORIUM: SOUND REPEATEDLY REFLECTED OFF THE WALLS & ROOF.    • HIGH REVERBERATION TIMES. • ESPECIALLY HIGH LOW-FREQUENCY REVERBERATION TIMES. BAROQUE THEATERS: 6 • DEEP-STAGE ARRANGEMENTS WITH FLY LOFTS, PROPS, EXTRAVAGANT DRAPERIES LED TO ACOUSTIC PROBLEMS DUE TO A LACK OF SOUND REFLECTING SURFACES AROUND THE PERFORMERS.  OPERA HOUSES:  OPERAS INCREASED THE NEED FOR ORCHESTRA ACCOMMODATIONS IN FRONT OF THE STAGE, WHICH DISTANCED THE AUDIENCE FROM THE PERFORMERS ON STAGE & COMPOUNDED PROBLEMS OF ACOUSTICAL BALANCE & CLEAR RECEPTION.  AUDIENCE ARRANGEMENTS CHANGED FROM EARLY CLASSICAL SEMI-ELLIPSE TO A U-SHAPE.  THE FRONT OF THE AUDITORIUM ENCLOSED THE FORESTAGE, ENABLING ACTORS OR SINGERS TO USE THE AUDITORIUM CEILING AS A SOUND REFLECTING SURFACE.  MULTIPLE BALCONIES WERE USED AS A SOLUTION TO PROBLEMS OF SCALE.  STACKED BALCONIES AND THE AUDIENCE ABSORBED HIGH- AND MIDFREQUENCY SOUND.   **WOOD PANELING WAS USED TO ABSORB LOW-FREQUENCY SOUND. ROCOCO TOWNHOUSES:  ROOMS WERE SPECIFICALLY DESIGN TO CREATE VARYING ACOUSTICAL PROPERTIES.  MARBLE ENTRANCE HALL: • RESOUNDED WITH THE RATTLE OF SIDEARMS AND THE CLATTER OF HIGH HEELS AS VISITORS WALKED ACROSS THE STONE FLOOR.  LARGE DINING HALL: •  ACOUSTICALLY ADAPTED FOR TABLE MUSIC. SALON: WITH DAMASK-PANELED WALLS WHICH ABSORBED SOUND AND SHORTENED REVERBERATION TIME, AND WOODEN DADOES WHICH GAVE THE RIGHT RESONANCE FOR CHAMBER MUSIC.  SMALLER ROOMS: •  DESIGNED FOR THE MORE FRAGILE TONES OF A SPINET. BOUDOIR: • DESIGNED WITH SOUND ABSORBING SURFACES THAT LOWER REVERBERATION TIME. • SUITED TO INTIMATE CONVERSATION. HUMAN HEARING • KNOW THE FOLLOWING: O THE FREQUENCY RANGE OF HUMAN HEARING (20-20,000 HZ). O THE FREQUENCY RANGE OF HUMAN SPEECH (125-8000 HZ). O THE THRESHOLD OF AUDIBILITY, LONG TERM HEARING LOSS, FEELING AND PAIN.   7  THE HUMAN HEARING RANGE IS FROM 0 DECIBELS WHICH IS THE THRESHOLD OF AUDIBILITY TO 130 DECIBELS WHICH IS THE THRESHOLD OF PAIN.  THE NORMAL LISTENING RANGE IS ABOUT 45 TO 85 DECIBELS.  THE THRESHOLD OF HEARING LOSS IS 75 TO 85 DECIBELS WITH LONG-TERM EXPOSURE.  HEALTH EFFECTS OF LONG-TERM EXPOSURE TO SOUND SOURCES BETWEEN 75 & 85 DECIBELS: • HEARING LOSS. • HEADACHE. • DIGESTIVE PROBLEMS. • HIGH BLOOD PRESSURE O CHARACTERISTICS OF FREQUENCY RECOGNITION.  DROPS AT LOW FREQUENCIES.  MAXIMUM SENSITIVITY IS AT 3000 TO 4000 HZ (-5 DB)- PRECISELY THE FREQUENCIES THAT CONTAIN THE MOST INFORMATION IN HUMAN SPEECH.  NORMAL LISTENING RANGE IS 150 TO 6000 HZ  **FREQUENCY RECOGNITION IS NONLINEAR O PERCEPTIBLE CHANGES IN SOUND LEVEL. (**3,6,10)  3 DB: BARELY PERCEPTIBLE  6 DB: CLEARLY PERCEPTIBLE  10 DB: TWICE AS LOUD O NOISE ANNOYANCE FACTORS  PROPORTIONAL TO THE LOUDNESS.  GREATER FOR HIGH-FREQUENCY SOUNDS THAN LOW FREQUENCY SOUNDS.  GREATER FOR INTERMITTENT (MOVING) THAN CONTINUOUS NOISE SOURCES.  GREATER FOR PURE-TONE THAN BROAD-BANDS NOISE SOURCES.  GREATER FOR MOVING OR UNLOCATABLE THAN FIXED SOURCES.  MUCH GREATER FOR INFORMATION BEARING NOISE. ROOM ACOUSTICS • KNOW THE FOLLOWING: O METHODS OF IMPROVING THE DIRECT SOUND PATH. O  RAKED SEATING  RAISING THE SOURCE (STAGE) IN HEIGHT.  PLACING THE AUDIENCE AS CLOSE AS POSSIBLE TO THE STAGE. PRINCIPLES & LIMITATIONS OF RAY-DIAGRAM ANALYSIS.    PRINCIPLES:  PROCEDURE FOR ANALYZING REFLECTED SOUND.  RAYS ARE DRAWN NORMAL TO THE SPHERICALLY PROPAGATING OF WAVES.  SPECULAR REFLECTION IS ASSUMED. 8  O LIMITATIONS  THE SPACE IS THREE-DIMENSIONAL BUT THE DIAGRAM IS TWO-DIMENSIONAL.  COMPLICATED BY VARIOUS SPEAKING POSITIONS.  NOT APPLICABLE TO LOW-FREQUENCIES (BELOW 250HZ). BEHAVIOR OF SOUND REFLECTED FROM FLAT, PARALLEL, INCLINED, CONVEX AND CONCAVE SURFACES.  FLAT  WHEN SOUND REFLECTS OFF A FLAT HORIZONTAL SURFACE, A DEGREE OF DIFFUSION IS PROVIDED.   PARALLEL  ROOM RESONANCE  FLUTTER ECHO INCLINED  BETTER DIFFUSION THAN FLAT  IF THE INCLINATION IS UP TOWARD THE AUDIENCE, SOUND IS PROJECTED DEEPER INTO THE ROOM.   CAN INCREASE USEFUL CEILING REFLECTIVE SURFACE. CONVEX  PROVIDES THE GREATEST DIFFUSION.  IN A DIFFUSE SOUND FIELD THE SOUND LEVEL REMAINS RELATIVELY CONSTANT THROUGHOUT THE SPACE WHICH IS EXTREMELY DESIRABLE FOR MUSIC.  CONCAVE  REFLECTED SOUND IS CONCENTRATED INTO CERTAIN AREAS.  CREATES HOT AND DEAD SPOTS ACOUSTICALLY.  FOCUSING AND CREEP O FACTORS EFFECTING REVERBERATION TIME.  ROOM VOLUME   ABSORBTION COEFFICIENTS   LARGER VOLUME, GREATER REVERBERATION GREATER ABSORPTION COEFFEICIENT, LOWER REVERBERATION TIME. SURFACE AREA OF THE ROOM  MORE SURFACE AREA, MORE ABSORPTION  INCREASE SURFACE AREA, DECREASE REVERBERATION TIME. • KNOW THE METHODS OF CONTROLLING THE FOLLOWING: O FLUTTER ECHO & ROOM RESONANCE.    SOUND ABSORBING TREATMENT.  NONPARALLEL-WALL SURFACES.  SOUND-DIFFUSING WALL MODULATION. 9 O CREEP.  SURFACE UNDULATIONS.  SOUND ABSORBING TREATMENT. O FOCUSING.  FLATEN THE CEILING SURFACE.  SOUND ABSORBING TREATMENT. • KNOW THE FOLLOWING: O THE DESIGN CONSIDERATIONS DISCUSSED IN CLASS FOR AUDITORIUMS DESIGNED FOR SPEECH.  COMPACT SHAPE & LOW ROOM VOLUME.  HELPS TO ACHIEVE SATISFACTORY LOUDNESS BY SHORTENING BOTH THE DIRECT & REFLECTED SOUND PATH.  RECOMMENDED VOLUME PER SEAT RATIO: •  LOW REVERBERATION TIME.  LONG REVERBERATION TIMES REDUCE SPEECH INTELLIGIBILITY  OPTIMUM REVERBERATION TIMES  RECOMMENDED REVERBERATION TIMES BETWEEN 250 AND 4000 HZ: •  80 TO 150 CUBIC FEET PER PERSON. CONFERENCE ROOM: 0.7 TO 1.1 SECONDS. • CLASSROOMS: 0.6 TO 0.8 SECONDS. • LECTURE HALLS: 0.7 TO 1.1 SECONDS. • THEATERS: 0.9 TO 1.4 SECONDS. SOUND ABSORBING TREATMENT:  ABSORPTION SHOULD BE CONSTANT WITHIN THE RANGE FREQUENCY RANGE FOR SPEECH.  IT IS PREFERABLE TO PLACE ABSORPTION ON SIDE WALLS RATHER THAN THE CEILING.  SHORT DISTANCE BETWEEN SPEAKER AND BACK ROW.  SO THAT LOUDNESS WILL BE SUFFICIENT THROUGHOUT THE ROOM AND THE AUDIENCE WILL HAVE THE ABILITY TO SEE THE PERSON TALKING.  • 90 FEET FOR DRAMA • 140 FEET FOR OPERA A SHORT DISTANCE BETWEEN THE SPEAKER & THE BACK ROW CAN BE ACHIEVED THROUGH STACKED BALCONIES.  SEATING  **SEATING SHOULD BE WITHIN 140 DEGREE ANGLE MEASURED AT THE LOCATION OF THE SPEAKER:   • HIGH FREQUENCIES ARE DIMINISHED BY 6 DECIBELS AT THE SIDES. • SPEECH WILL BE LOUDEST AT THE CENTER OF A ROOM. 10  SHORT-DELAY SOUND REFLECTIONS.  CEILING OR OVERHEAD SOUND-REFLECTING SURFACES REFLECTING DIRECTLY TO THE AUDIENCE.  SPEECH; EXCELLENT: 23 FEET OR LESS; GOOD: UP TO 34 FEET  DRAW SERIES OF RAYS FROM SPEAKER TO AUDIENCE IN PLAN AND SECTION  DASHED LINES INDICATE PREFERRED ORIENTATIONS OF A LECTURE ROOM  HIGH SIGNAL-TO-NOISE RATIOS: • ROOM SHAPED TO DIRECT SOUND FROM THE SPEAKER’S LOCATION TOWARD THE AUDIENCE. •  BACK WALL DESIGNED TO AVOID ECHOES AND HOT SPOTS. RAKED SEATING.  GREATER THAN 7 DEGREES TO PROVIDE GOOD SIGHT LINES AND REDUCE AUDIENCE ATTENUATION.   STAGGERED SEATING  STAGE SHOULD BE KEPT BELOW EYE LEVEL (44”) SO BELOW 40” NC25 OR LESS.  BACKGROUND NOISE LEVELS: • LEVELS FROM MECHANICAL SHOULD NOT EXCEED 34 DECIBELS OR A NOISE CRITERION OF NC-25. • ENCLOSING CONSTRUCTION SHOULD REDUCE INTRUDING NOISE TO BELOW THIS PREFERRED CRITERION TO AVOID INTERFERENCE WITH DESIRED SOUNDS & PREVENT DISTRACTIONS.  ELECTRONIC SPEECH REINFORCEMENT.  ELECTRONIC SPEECH REINFORCEMENT SHOULD BE USED WHEN SEATING EXCEEDS THE FOLLOWING FOR DRAMA:  • PROSCENIUM STAGE: 1000 SEATS • OPEN OR THRUST STAGE: 700 SEATS • AREA STAGE: 400 SEATS **ELECTRONIC SPEECH REINFORCEMENT SHOULD BE USED WHEN SEATING EXCEEDS THE FOLLOWING FOR LECTURE ROOMS: • 500 SEATS • SMALLER LECTURE ROOMS, COURT ROOMS, CONFERENCE ROOMS & THE LIKE MAY ALSO REQUIRE SOUND-REINFORCING SYSTEMS TO ASSIST WEAK-VOICED SPEAKERS & TO PROJECT RECORDED MATERIAL EVENLY. O THE METHODS OF CREATING CLARITY, INTIMACY, REVERBERANCE, WARMTH AND ENVELOPMENT DISCUSSED IN CLASS AND IN YOUR TEXTBOOK.    CLARITY:  ABILITY TO PERCEIVE MUSICAL DETAIL.  VARIES FROM CLEAR (OR DISTINCT) TO BLURRED (OR MUDDY). 11   ACOUSTICAL PROPERTIES REQUIRED TO ACHIEVE CLARITY(INTIMACY ALSO): • INITIAL-TIME-DELAY GAP LESS THAN 20 MS (23’). • USE OF SUSPENDED SOUND-REFLECTING PANELS. • LENGTH-TO-WIDTH RATIO LESS THAN 2. • AVOIDANCE OF DEEP UNDER-BALCONIES. USE OF SUSPENDED SOUND REFLECTING PANELS TO REDUCE THE TIME DELAY GAP.  LENGTH TO WIDTH RATIO: LESS THAN 2  DEEP UNDER-BALCONIES SHOULD BE AVOIDED • HEIGHT OF OPENING IS MAXIMUM DEPTH OF UNDER-BALCONY • IN CONCERT HALLS THE DEPTH OF THE UNDER-BALCONY SHOULD NOT EXCEED THE HEIGHT OF THE OPENING. • IN AN OPERA HOUSE THE DEPTH SHOULD NOT EXCEED 1.5 TIMES THE HEIGHT. • IN MOTION PICTURE THEATERS, UNDER-BALCONIES SHOULD NOT EXCEED 3H, ALTHOUGH 2H IS PREFERRED. •  FLYING BALCONY CAN BE USED REVERBERANCE:    DEFINITION • DEGREE OF PERCEIVED SOUND REFLECTION. • RANGE IS FROM LIVELY TO DEAD. ACOUSTICAL PROPERTIES REQUIRED TO ACHIEVE REVERBERANCE: • VOLUME • SHAPE & PROPORTION • SOUND-REFLECTING WALLS & CEILINGS • AUDIENCE CAPACITY & SEAT SPACING VOLUME. • 300 CF PER PERSON FOR RECTANGULAR HALLS • 450 CF PER PERSON FOR SURROUND HALLS.  FURNISHINGS & FINISHES: SOUND-REFLECTING WALLS & CEILINGS.  AUDIENCE CAPACITY & SEAT SPACING: • LIMIT SEATING DENSITY TO 6.5 TO 9 SF PER PERSON INCLUDING AISLES, BECAUSE THE MORE THE AUDIENCE IS SPREAD OUT, THE MORE SOUND IT ABSORBS.     REVERBERATION TIME: 2 TO 2.5 SECONDS  ADJUSTABLE PANELS ADAPT FOR MULTIPURPOSE WARMTH (HIGH BASS RATIO) 12  FULLNESS OF BASS FREQUENCIES RELATIVE TO MID-FREQUENCY RESPONSE (LONGER DURATION OF REVERBERANCE AT BASS COMPARED TO MID- AND TREBLE FREQUENCIES).  RANGE IS FROM WARM TO COLD.  PROPERTIES REQUIRED TO PRODUCE WARMTH:  • BASS RATIO GREATER THAN 1.2. • THICK, HEAVY ENCLOSING SURFACES. • HEIGHT-TO-WIDTH RATIO GREATER THAN 0.7. • COUPLED SPACES. BASS RATIO: • THE BASS RATIO IS THE REVERBERATION TIME AT LOW FREQUENCIES (I.E., AVERAGE OF REVERBERATION AT 125 AND 250 HZ) DIVIDED BY THE MID-FREQUENCY REVERBERATION TIME. • FOR EXAMPLE, IF THE MID-FREQUENCY REVERBERATION TIME IS 2 SECONDS AND THE LOW-FREQUENCY REVERBERATION TIME IS 2.4 SECONDS, THE BASS RATIO WILL BE (2.4/2) = 1.2. • USE THICK, HEAVY ENCLOSING SURFACES WHICH REFLECT LOW FREQUENCY SOUND. • AVOID THIN (E.G. WOOD PANELS LESS THAN ¾-IN THICK) OR LIGHTWEIGHT MATERIALS, WHICH ABSORB LOW-FREQUENCY SOUND ENERGY BY PANEL ACTION.  INTIMACY.  DEGREE OF IDENTIFICATION WITH THE PERFORMANCE.  RANGE IS FROM INTIMATE TO REMOTE.  ACOUSTICAL PROPERTIES REQUIRED TO ACHIEVE INTIMACY (SAME AS CLARITY): • INITIAL-TIME-DELAY GAP LESS THAN 20 MS (23’). • LENGTH-TO-WIDTH RATIO LESS THAN 2 OR USE OF SUSPENDED SOUNDREFLECTING PANELS. •  AVOIDANCE OF DEEP UNDERBALCONIES. ENVELOPMENT:  FEELING OF IMMERSION IN SOUND; DEGREE TO WHICH ONE FEELS SURROUNDED BY THE SOUND.  RANGE IS FROM RICH TO POOR OR EXPANSIVE TO CONSTRICTED. O THE PROPERTIES OF RECTANGULAR SHOE-BOX SHAPED, SQUARE, CENTRALIZED, FAN AND HORSESHOE SHAPED HALLS  RECTANGULAR SHOEBOX.  DESCRIPTION: •   LENGTH-TO-WIDTH RATIO OF 2:1 TO 1.2:1 13 • HEIGHT TO WIDTH PROPORTIONS OFF-SQUARE, WITH WIDTH EXCEEDING HEIGHT.  ACOUSTICAL PROPERTIES: • GOOD SIDE WALL REFLECTIONS & ENVELOPMENT. • GOOD BLEND OF SOUND BECAUSE THE AUDIENCE GROUPING IS CENTRAL TO ORCHESTRA. • LARGE AUDIENCES REQUIRE DEEP BALCONIES. • POOR INTIMACY AT LARGE SCALES (FEELING OF SITTING AT THE END OF A BOWLING ALLEY). •  SQUARE OR NEAR SQUARE.  DESCRIPTION: •   MULTI-USE CAPABILITY LIMITED. PROPORTIONS 1:1 TO 1:1.2 ACOUSTICAL PROPERTIES: • GREATER FLEXIBILITY IN SEATING ARRANGEMENTS. • NECKING AT THE STAGE IMPROVES SIDE REFLECTIONS. • OVERHEAD REFLECTING PANELS OVER STAGE REQUIRED FOR CLARITY. • GOOD INTIMACY. CENTRALIZED GEOMETRIES:    DESCRIPTION: • HEXAGONAL • OCTAGONAL • CIRCULAR • POLYGONAL ACOUSTICAL PROPERTIES: • PERMITS LARGER AUDIENCES THAN A RECTANGULAR SHAPE. • CAUTION IS REQUIRED BECAUSE OF FOCUSING & CROSS-REFLECTIONS CHARACTERISTICS: • BRING THE AUDIENCE CLOSE TO THE STAGE IN LARGE SCALE HALLS. • ONE OF THE FIRST HALLS OF THIS TYPE WAS THE BERLIN PHILHARMONIE, BY HANS SCHAROUN. • IRREGULARLY SHAPED WALL & CEILING SURFACES USED TO DISTRIBUTE SOUND & PREVENT FOCUSING. • UNLESS A RELATIVELY SMALL PORTION OF THE SEATING IS BEHIND THE ORCHESTRA, ELECTRONIC SUPPLEMENT OF NATURAL SOUND IS NECESSARY.  FAN.  DESCRIPTION: •   AUDITORIUM FANS OUT FROM THE STAGE. 14 •  POPULAR IN THE U.S. DURING THE 1970’S. ACOUSTICAL PROPERTIES: • SUCCESSFULLY PUTS A LOT OF PEOPLE NEAR THE STAGE FOR CLOSE VISION, CLARITY & INTIMACY.  • VARIABLE SOUND QUALITY BETWEEN SIDES & CENTER. • ALMOST A TOTAL LACK OF GOOD SIDE WALL REFLECTIONS. HORSESHOE.  DESCRIPTION: • AUDITORIUM IS HORSESHOE SHAPED WITH THE OPEN END FACING THE STAGE. •  TRADITIONAL FORM FOR OPERA. ACOUSTICAL PROPERTIES: • GOOD INTIMACY. • LACK OF ADEQUATE REVERBERATION. • FOCUSING REFLECTIONS FROM THE CONCAVE REAR WALL. • KNOW THE FOLLOWING: O OPTIMUM REVERBERATION TIMES FOR SPEECH AND MUSIC:  SPEECH (0.6 TO 1.3)  MUSIC (1.6 TO 2.4) O KNOW THE OPTIMUM ROOM VOLUME FOR SPEECH AND MUSIC:  SPEECH: 110 CUBIC FEET PER PERSON  MUSIC: 275 CUBIC FEET PER PERSON ELECTRONIC SOUND SYSTEMS • KNOW THE FOLLOWING: O KNOW THE SIZE AT WHICH A BUILDING REQUIRES AN ELECTRONIC SOUND SYSTEM.  SPACES LARGER THAN 60,000 CUBIC FEET.  LECTURE ROOM OF MORE THAN 500 SEATS.  DISTANCE GREATER THAN 60 FEET O THE FUNCTION OF MICROPHONES, AMPLIFIERS, CROSSOVER NETWORK, WOOFERS & TWEETERS.  MICROPHONES  PICK UP THE SOUND ENERGY RADIATED BY THE SOURCE & CONVERTS IT INTO ELECTRIC ENERGY & FEEDS IT INTO THE AMPLIFIER.     AMPLIFIER  INCREASES THE MAGNITUDE OF THE ELECTRONIC SIGNAL.  SPEECH: 80 DB  LIGHT MUSIC: 95 DB  SYMPHONIC MUSIC: 105 DB CROSSOVER NETWORK. 15  DISTRIBUTES THE ELECTRIC ENERGY TO HIGH- AND LOW-FREQUENCY LOUDSPEAKERS AT THE PROPER LEVEL.  WOOFERS.   LOW-FREQUENCY LOUDSPEAKERS IN A LARGE CABINET ENCLOSURE. TWEETERS.  HIGH-FREQUENCY HORNS WITH A FLARED SHAPE TO GIVE DIRECTION TO SHORTER WAVELENGTHS. O KNOW THE CHARACTERISTICS OF CENTRAL CLUSTER, SPLIT CLUSTER, DISTRIBUTED, COLUMN, AND SEAT-INTEGRATED LOUDSPEAKER SYSTEMS.  CENTRAL CLUSTER.  20 FEET FROM SPEAKER TO LOUDSPEAKER  D2/D1 <2 (SEE POWERPOINT) •  EVALUATION O REALISM: EXCELLENT O VISIBILITY: HIGH OR MEDIUM IF RECESSED O COST: LOW SPLIT CLUSTER.  DESCRIPTION: • USED IN ROOMS WITH TWO MAIN SPEAKING POSITION (EG. CHURCH WITH LECTERN AND PULPIT, SEPARATED AT LEFT & RIGHT). • THE SYSTEM WORKS BEST WHEN THE CLUSTER AMPLIFIES SPEECH FROM THE CLOSEST SOURCE POSITION ONLY.   EVALUATION: • REALISM: GOOD • VISIBILITY: CAN BE MEDIUM • COST: MODERATE DISTRIBUTED (OVERHEAD).  LESS THAN 20 FEET CEILING HEIGHT  SEVERAL SMALL SPEAKERS THROUGHOUT CEILING  SPACING: 1.4 TIMES CEILING HEIGHT MINUS 4 (SEATED) OR MINUS 6 (STANDING)   EVALUATION: • REALISM: POOR • VISIBILITY: LOW IF RECESSED; MEDIUM OR HIGH IF SUSPENDED. • COST: LOW TO MODERATE COLUMN (DISTRIBUTED ALONG LENGTH OF ROOM).  DESCRIPTION: CONSISTS OF A LINEAR ARRAY OF CONE LOUDSPEAKERS (USUALLY VERTICAL WITH ONE ABOVE THE OTHER) TO CONCENTRATE SOUND INTO A NARROW VERTICAL BEAM.   16   EVALUATION: • REALISM: FAIR. • VISIBILITY: MEDIUM. • COST: MODERATE TO HIGH. SEAT-INTEGRATED.  DESCRIPTION: • CONSISTS OF A NUMBER OF LOUDSPEAKERS (SPACED 5 TO 8 FEET APART) WHICH ARE LOCATED IN THE BACKS OF SEATS OR PEWS. • THIS SYSTEM CAN BE USED IN ROOMS WHERE REVERBERATION TIMES ARE TOO LONG FOR SPEECH.  EVALUATION: • REALISM: POOR. • VISIBILITY: LOW. • COST: HIGH. ABSORPTION • KNOW THE CHARACTERISTICS OF THE FOLLOWING: O FIBROUS OR POROUS ABSORBERS.  DESCRIPTION:  ABSORBS BY THE FRICTIONAL DRAG PRODUCED BY MOVING THE AIR IN SMALL SPACES WITHIN THE MATERIAL.  ABSORPTION DETERMINED BY:  THICKNESS  POROSITY  AIR PATH MUST EXTEND FROM ONE SIDE TO THE OTHER.  EFFECTIVE FOR HIGHER AND MID FREQUENCIES  AIR SPACE HELP WITH LOW FREQUENCY ABSORBTION  INCREASE THE SURFACE AREA TO INCREASE THE ABSORBTION O PANEL RESONATORS.  DESCRIPTION:  BUILT WITH A MEMBRANE SUCH AS PLYWOOD IN FRONT OF A SEALED AIR SPACE . THE PANEL IS SET IN MOTION BY THE ALTERNATING PRESSURE OF THE IMPINGING SOUND WAVE. THE SOUND WAVE IS CONVERTED INTO HEAT THROUGH INTERNAL VISCOUS DAMPING.  CONVERT SOUND ENERGY TO HEAT ENERGY THROUGH DIAPHRAGM ACTION  NOT GOOD FOR MID AND HIGH FREQUENCY, BEST FOR LOW FREQUENCIES  VARYING PANEL THICKNESS OR AIR SPACE CAN ADJUST FOR SPECIFIC FREQUENCIES    APPLICATION: 17  USED WHERE EFFICIENT LOW-FREQUENCY ABSORPTION IS REQUIRED AND MIDDLE- AND HIGH-FREQUENCY ABSORPTION IS UNWANTED OR PROVIDED BY ANOTHER TREATMENT. O HELMHOLTZ RESONATORS.  AIR CAVITY WITHIN A MASSIVE ENCLOSURE, CONNECTED TO THE SURROUNDINGS BY A NARROW NECK OPENING.  METHOD OF ABSORPTION:  THE IMPINGING SOUND CAUSES THE AIR IN THE NECK TO VIBRATE & THE MASS BEHIND CAUSES THE ENTIRE CONSTRUCTION TO RESONATE AT A PARTICULAR FREQUENCY. AT THAT FREQUENCY ABSORPTION IS VERY HIGH & DROPS SHARPLY ABOVE AND BELOW THIS FREQUENCY.   ADJUSTABLE TO FREQUNCIES; MANIPULATE CAVITY SIZE AND SLOT SIZES APPLICATION:  EXTREMELY USEFUL WHEN A SINGLE MAJOR FREQUENCY IS PRESENT.  USED IN: • GYMNASIUMS • SWIMMING POOLS • BOWLING LANES • INDUSTRIAL BUILDINGS • MECHANICAL ROOMS O TRANSONDENT FACINGS.  DESCRIPTION:  PERFORATED FACINGS WHICH ARE SOMEWHAT TRANSPARENT TO SOUND.  THEY ARE SOMETIMES PLACED IN FRONT OF A SOUND ABSORBING MATERIAL TO PROTECT OR CONCEAL IT.   SMALL HOLES FOR LOW FREQUENCIES, LARGE FOR HIGH FREQUENCIES  NOT SOUND ABSORBING EVALUATION:  FACINGS TEND TO REDUCE THE EFFECTIVENESS OF SOUND-ABSORBING MATERIALS BY REFLECTING HIGH-FREQUENCY SOUND WAVES.  IN GENERAL, THE LOWER THE PERCENTAGE OF OPEN AREA IN THE FACING, THE LESS ABSORPTION OF HIGH-FREQUENCY SOUND.  THICKER FACINGS HAVE HIGHER REFLECTIONS OF HIGH FREQUENCY SOUNDS DO TO INCREASE SURFACE AREA ISOLATION • KNOW THE DETERMINANTS OF TRANSMISSION LOSS O BARRIER MASS.  FOR EVERY DOUBLING OF MASS, THE TL INCREASES BETWEEN 4 AND 6 DECIBELS, DEPENDING ON THE POROSITY AND STIFFNESS OF A MATERIAL.   18 O STIFFNESS.  RIGIDITY IN A PANEL RESISTS DAMPING AND ASSISTS VIBRATIONS MAKING IT A POOR INSULATOR.  DETERMINANTS OF STIFFNESS:  MATERIAL COMPOSITION: • A HOMOGENEOUS MATERIAL WITH A HIGH MODULUS OF ELASTICITY HAS GREAT COHESIVENESS BETWEEN ITS MOLECULES. • AS SOON AS ONE MOLECULE IS SET IN MOTION BY THE INCIDENT SOUND, THE MOTION IS PASSED TO THE NEXT & SO ON, MAKING STIFF MATERIALS EXCELLENT CONDUCTORS OF SOUND.  RIGIDITY OF MOUNTING: • WHETHER THE BARRIER IS TIGHTLY OR LOOSELY HELD. THE TIGHTER THE MOUNTING THE GREATER THE SOUND CONDUCTION. O CONSTRUCTION (LAYERING, AIR SPACES, SOUND ABSORBING MATERIALS & INTERCONNECTIONS)  LAYERING.  BARRIERS CONSTRUCTED OF TWO SEPARATE LAYERS WITHOUT RIGID INTERCONNECTION PERFORM BETTER THAN THE CALCULATED TL BASED ON MASS ALONE.  AIR CAVITIES.  IMPROVES PERFORMANCE THROUGHOUT THE FREQUENCY RANGE.  TL INCREASES WITH THE WIDTH OF THE AIR SPACES AT THE RATE OF APPROXIMATELY 5 DECIBELS PER DOUBLING.  SOUND-ABSORBING MATERIALS.  INTERCONNECTIONS.  THE PERFORMANCE OF COMPOSITE BARRIERS IS REDUCED BY ANY RIGID INTERCONNECTION BETWEEN LEAVES. O **IDENTIFY AN IDEAL WALL ASSEMBLY FOR BLOCKING AIRBOURNE SOUND  HIGH MASS, LOW STIFFNESS, LAYERED CONSTRUCTION • KNOW THE FOLLOWING: O PRINCIPLES OF SOUND LEAKS.  THE OVERALL PERFORMANCE OF A COMPOSITE WALL IS STRONGLY AFFECTED BY ITS WEAKER COMPONENT.  FOR EXAMPLE:  HAIRLINE CRACK DEGRADES A WALL 6 DECIBELS.  KEYHOLE 3 DECIBELS. O METHODS OF CONTROLLING LEAKS FROM WINDOWS AND DOORS.    NON-HARDENING CAULK  INSULATING 19  LAMINATED GLASS  GASKET  NO LOUVERS IN DOORS  SOID CORE AS OPPOSED TO HOLLOW CORE  THRESHOLDS O METHODS OF CONTROLLING FLANKING.  BARRIERS BETWEEN SENSITIVE ROOMS  RUN DUCTWORK IN COORIDOR  SOUND ABSORBING MATERIAL IN DUCTWORK • KNOW THE FOLLOWING: O METHODS OF ACHIEVING SPEECH PRIVACY IN ENCLOSED ROOMS AND  ENCLOSED ROOMS  ASSEMBLY WITH HIGH STC  AVOID AND CONTROL OPEN PLENUMS  ROOM ABSORPTION  AREA OF THE PARTITION BETWEEN THE TWO ROOMS  ACOUSTICAL ZONING • CAREFUL PLACEMENT WITH FUNCTIONAL PLANING O OPEN PLANS.  SCREENS.  SOUND ABSORBING FINISHES.  CEILING TREATMENT •  GREATER EFFECT WITH LARGER SURFACE AREA WALL TREATMENT • SOUND-ABSORBING WALL PANELS EXTENDING FROM 2’ TO 6’ ABOVE THE FLOOR.  WINDOW TREATMENT: • • THICK, SOUND-ABSORBING CURTAINS (GREATER THAN 8 OZ./YD2. WIDE SLAT, PERFORATED VERTICAL BLINDS (GREATER THAN 3” WIDE) WITH SOUND ABSORBING CORES.  WORKSTATION LAYOUTS.  SOUND MASKING.  SOUND INTRODUCED TO INCREASE BACKGROUND NOISE O THE PROPER DESIGN OF SCREENS.  NRC > 0.80 & STC = 25.  SCREENS LESS THAN 4 FEET ARE NORMALLY NOT EFFECTIVE BARRIERS.  2 X WIDER THAN IT IS TALL O THE PLACEMENT OF SOUND ABSORBING MATERIALS.    CEILING TREATMENT 20   GREATER EFFECT WITH LARGER SURFACE AREA WALL TREATMENT  SOUND-ABSORBING WALL PANELS EXTENDING FROM 2’ TO 6’ ABOVE THE FLOOR. O PROPER LAYOUT OF WORK STATIONS.  FACE WORKSTATIONS AWAY FROM EACH OTHER IF POSSIBLE  5 DB DROP IF AT 90 DEGREES, 10 DB DROP IF FACING AWAY  BARRIER BETWEEN SPEAKER AND WORKSTATION  STAGGERING WORKSTATIONS • KNOW THE FOLLOWING: O THE FUNDAMENTALS OF IMPACT ISOLATION.  DESCRIPTION:  IMPACT NOISES ARE ERRATIC AND CAN BE CAUSED BY WALKING (HARD HEEL FOOTFALL), ROLLING CARTS, DROPPED OBJECTS, SHUFFLED FURNITURE, SLAMMED DOORS AND THE LIKE.  IMPACTS ON FLOORS ARE RADIATED DIRECTLY DOWNWARD.  THEY ALSO CAN BE TRANSMITTED HORIZONTALLY THROUGH THE STRUCTURE AND BE RERADIATED AT DISTANT LOCATIONS.  IT IS BEST TO PREVENT IMPACT SOUND ENERGY FROM ENTERING THE BUILDING STRUCTURE.  AT LEAST AS SERIOUS A PROBLEM AS AIRBORNE NOISE BECAUSE:  HIGH INTENSITY ENERGY IS INTRODUCED DIRECTLY INTO THE STRUCTURE.  SINCE THE STRUCTURE MUST HAVE INTEGRITY TO CARRY LOADS, DISCONTINUITIES (WHICH ATTENUATE SOUND) ARE COMPLEX & EXPENSIVE.   STRUCTURE CONSTITUTES A NETWORK OF SOUND PATHS. CUSHION IMPACT.  CUSHIONED FLOORS: • STRUCTURE-BORNE SOUND CAN BE ISOLATED BY CUSHIONING THE IMPACT. • CARPETING AND RESILIENT RUBBER FLOOR TILES CAN BE USED TO CUSHION THE IMPACT. • THEY ARE MOST EFFECTIVE AS ISOLATORS OF MID- AND HIGHFREQUENCY IMPACT NOISES SUCH AS “CLICKS” FROM FOOTSTEPS. • LOW-FREQUENCY “THUDS” FROM THINGS BEING DROPPED STILL MAY BE TRANSMITTED THROUGH CONSTRUCTIONS HAVING CARPETING AND RESILIENT RUBBER FLOOR TILES.  FLOAT FLOOR    DESCRIPTION: 21 • FLOATED FLOORS ARE SLABS (OR FLOOR ASSEMBLIES) WHICH ARE COMPLETELY SEPARATED FROM THE STRUCTURAL SLAB BY A RESILIENT UNDERLAYMENT OR BY RESILIENT ISOLATORS.  PARTITIONS: • PARTITIONS BORDERING FLOATED FLOORS SHOULD NOT SET ON THE FLOATED FLOOR. • THIS RESULTS IN EITHER AN OVER COMPRESSED RESILIENT ISOLATOR OR A SHEAR FAILURE IN THE FLOATED SURFACE.  SUSPEND CEILING.  SUSPENDED CEILINGS: • THE CEILING IS SUSPENDED FROM ISOLATION HANGERS WITH A 6” OR MORE AIR SPACE. •  OFTEN FIBROUS INSULATION IS PLACED IN THE PLENUM. ISOLATE VIBRATING MEMBERS.  ISOLATE ALL PIPING: • ALL RIGID, VIBRATING ELEMENTS, SUCH AS PIPING MUST BE ISOLATED AND CAULKED WITH RESILIENT SEALING TO PREVENT STRUCTUREBORNE SOUND TRANSMISSION.  WHICH IMPROVEMENTS RESULT IN THE HIGHEST IIC. • THE IIC RATINGS VARY FROM 25 FOR A BARE CONCRETE SLAB TO 57 FOR CONCRETE FLOATED FLOOR CONSTRUCTION. • TO ACHIEVE HIGH IIC’S USE SOFT FLOOR SURFACES, CEILINGS SUSPENDED UNDER SLABS, FLOATED FLOORS, OR ALL THREE OF THESE IMPACT CONTROL MEASURES. • AVOID HARD SURFACES SUCH AS BARE CONCRETE, TERRAZZO, VINYL TILES AND LINOLEUM. • IN THE UNITED STATES, THE IIC RATING METHOD IS RECOMMENDED BY THE FEDERAL HOUSING ADMINISTRATION (FHA) AS A RATING OF IMPACT SOUND ISOLATION EFFECTIVENESS. • THE IIC METHOD IS BASED ON MEASUREMENTS OF THE SOUND PRESSURE LEVELS PRODUCED IN A ROOM DIRECTLY BELOW THE TEST FLOOR ON WHICH A STANDARD TAPPING MACHINE IS OPERATING. • IIC TESTS ARE MEASURED AT 16 FREQUENCY BANDS CENTERED FROM 100 HZ TO 3150 HZ. • A HIGH IIC NUMBER DOES NOT NECESSARILY MEAN THAT IMPACT ISOLATION WILL BE SATISFACTORY BECAUSE THE IIC METHOD DOES NOT CONSIDER IMPACT SOUND TRANSMISSION BELOW 100 HZ   22 • IMPACT NOISE PROBLEMS CAN ARISE AT LOW FREQUENCIES, COMMONLY OCCURRING WITH LIGHTWEIGHT STEEL OR WOOD FRAME FLOORING SYSTEMS. • WHERE IMPACT ISOLATION IS REQUIRED, AVOID ESPECIALLY LONG UNSUPPORTED FLOOR SPANS AND EXCESSIVE FLOOR DEFLECTION. CONTROL • KNOW THE FOLLOWING: O THE METHODS OF QUIETING MACHINE NOISE, DUCT NOISE, PLUMBING SOURCES, TRANSFORMER NOISE AND BALLAST NOISE.  QUIETING MACHINES:  DAMPING. • THE RIGID COUPLING OF THE VIBRATING SOURCE TO A LARGE MASS (FREQUENTLY CALLED AN INERTIA BLOCK). • MUCH OF THE ENERGY IS ABSORBED AND DISSIPATED AS FRICTION, THE REMAINDER RESULTS IN LOWER-AMPLITUDE VIBRATION.  ISOLATION. • SUPPORTING THE VIBRATING MASS OR ELEMENT ON RESILIENT SUPPORTS. • THE EQUIPMENT CONTINUES TO BE A SOURCE OF AIRBORNE SOUND & VIBRATIONS, BUT THE FEELABLE VIBRATIONS IN THE STRUCTURE AND THE STRUCTURE-BORNE SOUND WILL BE CONSIDERABLY REDUCED.  RESILIENT MATERIALS: • CORK • RIBBED NEOPRENE PADS • PRE-COMPRESSED GLASS FIBER PADS. • STEEL SPRINGS. O MOST RESILIENT OF THE COMMONLY USED ISOLATORS BECAUSE THEY CAN PROVIDE THE LARGEST DEFLECTIONS. O  THEY CAN EFFECTIVELY ISOLATE LOW-FREQUENCY VIBRATIONS. BOILERS: • COMBUSTION AIR BLOWER IS USUALLY THE PRIMARY SOURCE OF NOISE & LOW-FREQUENCY VIBRATION. • MOST AIRBORNE NOISE IS RADIATED FROM THE FRONT FACE OF THE UNIT & FROM THE AIR & FUEL SUPPLY PATHS. • A FLEXIBLE CONNECTION SHOULD BE INSTALLED IN THE SMOKE VENT, BETWEEN THE BOILER & THE EXHAUST STACK. • FOR BOILERS ON UPPER FLOORS NEAR CRITICAL AREAS, A STEEL MOUNTING FRAME SUPPORTED BY NEOPRENE OR STEEL SPRINGS.   23 • GAS & ELECTRICAL CONNECTIONS SHOULD USE BRAIDED FLEXIBLE TUBING & FLEXIBLE ARMORED ELECTRICAL CONDUIT.  COMPRESSORS: • LARGE, LOW-SPEED RECIPROCATING COMPRESSORS SHOULD BE ISOLATED BY SPRINGS & INERTIA BLOCKS TO REDUCE THE AMPLITUDE OF THE VIBRATIONS. • HIGH-SPEED CENTRIFUGAL COMPRESSORS REQUIRED LESS ISOLATION. • CENTRIFUGAL COMPRESSORS MAY REQUIRE ISOLATION BY SPRINGS BUT OFTEN CAN BE ISOLATED PROPERLY WITH SEVERAL LAYERS OF RIBBED NEOPRENE.  COOLING TOWERS: • COOLING TOWER VIBRATION INVOLVES LOW-FREQUENCY VIBRATION OF THE RELATIVELY SLOW-TURNING PROPELLER-TYPE FANS AS WELL AS HIGH-FREQUENCY IMPACT NOISE FROM FALLING WATER. • IDEALLY THE MOTOR, DRIVE SHAFT, GEAR REDUCER & PROPELLER SHOULD BE RIGIDLY SUPPORTED, WITH THIS SUPPORT ELEMENT IN TURN RESILIENTLY ISOLATED FROM THE TOWER. • A MORE COMMON APPROACH IS TO SUPPORT THE ENTIRE COOLING TOWER BY STEEL SPRINGS & RIBBED NEOPRENE MOUNTS.  **DUCT SYSTEM NOISE REDUCTION  INSULATION: • LINING DUCTS WITH ACOUSTICAL MATERIALS REDUCES CROSS-TALK BETWEEN ROOMS. •  BOTH SUPPLY & RETURN DUCTS SHOULD BE LINED. AIR VELOCITY: • ALLOWABLE VELOCITIES INCREASE AS THE DISTANCE FROM THE TERMINAL DEVICE INCREASES.  • RETURNS VELOCITIES CAN BE SLIGHTLY HIGH THAN SUPPLY DUCTS. • REDUCING VELOCITY INCREASES THE SIZE OF THE DUCTWORK TURNS: • SHOULD ALWAYS BE SMOOTH. • FANS SHOULD BE LOCATED SUFFICIENT DISTANCES AWAY SO DISTURBED FLOW CAN DISSIPATE. •  LINING TURNS WITH GLASS FIBER CAN REDUCE NOISE. DIFFUSERS: • REMOVING THE DAMPERS & GRILLE FROM THE BRANCH DUCT CAN REDUCE AIRFLOW NOISE FROM TURBULENCE BY MORE THAN 10 DB AT MID-FREQUENCIES.   24 • WHEN A SMALL DUCT OPENS INTO THE LARGE VOLUME OF A ROOM, LOW-FREQUENCY DUCT-BORNE SOUND ENERGY IS REFLECTED BACK INTO THE END OF THE DUCT (CALLED END REFLECTION).  MECHANICAL ROOMS: • SHOULD BE LOCATED ON OR BELOW GRADE, AWAY FROM ACOUSTICALLY SENSITIVE AREAS. • SHOULD HAVE SUFFICIENT FLOOR SPACE AND VERTICAL CLEARANCE FOR SMOOTH OPERATION, INSPECTION & MAINTENANCE OF ALL EQUIPMENT. • DO NOT PLACE FANS CLOSE TO WALLS WHERE SOUND ENERGY CAN BUILD UP IN THE NARROW SPACE BETWEEN FAN & WALL. • CONTROL OF SOUND BUILDUP CAN BE ACCOMPLISHED BY TREATING CEILING & WALLS WITH THICK, SOUND-ABSORBING MATERIALS (GLASS FIBERBOARD OR MINERAL FIBERBOARD).  TRANSPORTATION SYSTEMS.  ELEVATORS •  CORRIDORS AROUND THEM PLUMBING NOISE SOURCES.  PIPES: • SHOULD BE LOCATED AWAY FROM ACOUSTICALLY SENSITIVE AREAS SUCH AS AUDITORIUMS, THEATERS, CONFERENCE ROOMS AND PRIVATE OFFICES. • LEAST NUMBER OF TURNS. O   RESILIENT ISOLATION. PENETRATIONS • WALL • STUD • FLOOR WATER FLOW VELOCITIES: • TO PREVENT WATER FLOW NOISE GENERATED BY TURBULENCE, VELOCITIES SHOULD BE CONTROLLED BY USING LARGE PIPE SIZES AND LARGE RADIUS ELBOWS.  WATER HAMMER: • CAUSED WHEN A RAPIDLY CLOSED VALUE ABRUPTLY STOPS A MOVING COLUMN OF WATER. • THE RESULTING FORWARD AND BACKWARD WATER SURGE WITHIN THE PIPING PRODUCES POUNDING NOISES CALLED WATER HAMMER. • SPRING-OPERATED VALUE: PREVENT WATER HAMMER BY SLOWLY CLOSING THE VALUE STEMS.   25  TUBS & SHOWERS: • THE SOUND OF RUNNING WATER IN A BATH TUB OR SHOWER CAN BE ISOLATED THROUGH THE USE OF FLOATED FLOOR CONSTRUCTION OR RESILIENT UNDERLAYS, SUCH AS CORK, RUBBER OR NEOPRENE.  ELECTRICAL NOISE SOURCES:  TRANSFORMERS. • CONTROLLING TRANSFORMER NOISE: O OIL & SILICONE-FILLED UNITS ARE NORMALLY QUIETER THAN DRY-TYPE.  O MOUNT UNITS ON VIBRATION ISOLATORS. O CAVITY RESONATORS BALLASTS. • HID: O NOSIER THAN FLUORESCENT. O GENERALLY LESS TROUBLESOME, BEING COUPLED TO SMALL RADIATING BODIES & GENERALLY MOUNTED HIGHER. • FLUORESCENT: O QUIETER THAN HID BALLASTS BUT MOUNTED TO A LARGER RADIATING BODY. O WHEN A SMALL VIBRATING SOURCE IS RIGIDLY COUPLED TO A LARGER BODY, NOISE IS AMPLIFIED BECAUSE OF INCREASED SOURCE-TO-AIR COUPLING. • NOISE CONTROL: O USE OF ABSORPTIVE MATERIALS IN PLENUMS. O FLEXIBLE CONDUIT CONNECTION TO FIXTURE. O RESILIENT FIXTURE HANGING. O REMOTE MOUNTING. O BALLAST RATING.  A : 24 DECIBELS  B : 30 DECIBELS  C : 36 DECIBELS  D : 42 DECIBELS  E : 48 DECIBELS O THE RELATIVE EFFECTIVENESS OF TREES, EARTH BERMS AND THIN WALL BARRIERS IN CONTROLLING OUTDOOR NOISE.  TREES & VEGETATION.  NORMALLY NOT AN EFFECTIVE NOISE CONTROL BARRIER.  DENSE PLANTINGS OF TREES & SHRUBS AT LEAST 100 FEET DEEP CAN PROVIDE 7 TO 11 DECIBELS OF SOUND ATTENUATION FROM 125 TO 8000 HERTZ.   26  DECIDUOUS TREES PROVIDE ALMOST NO SOUND ATTENUATION ONCE THEIR LEAVES HAVE FALLEN.  EARTH BERMS.  WHEN COMPLETELY COVERED BY GRASS OR OTHER SOUND-ABSORBING PLANT MATERIAL THEY CAN REDUCE NOISE BY 5 TO 10 DECIBELS.  THE EFFECTIVENESS OF EARTH BERMS CAN BE REDUCED BY REFLECTIVE TOP SURFACES AND TREES WHICH CAN REDUCE ATTENUATION BY 5 DECIBELS.  THIN WALL BARRIERS.  **PLACE BARRIERS AS CLOSE AS POSSIBLE TO THE SOURCE OF SOUND OR THE RECEIVER. •  WORST LOCATION IS DIRECTLY IN THE MIDDLE THE GREATER THE HEIGHT OF THE BARRIER ABOVE THE ACOUSTICAL LINE OF SIGHT THE GREATER THE SOUND ATTENUATION.  BARRIERS SHOULD BE SOLID & AIR TIGHT. O KNOW THE SELF-PROTECTING BUILDING FORMS DISCUSSED IN CLASS.  ATRIUMS.  HOLLOW OUT AREA INSIDE AND SURROUND WITH FUNCTIONS AS TO MINIMIZE OUTSIDE CONNECTION.  RECESSED FLOORS.  MUST HAVE SOLID BALCANINES TO BE EFFECTIVE (SOLID RAILINGS)  INTERUPTING SOUND PATH AND PLACING LISTENER FURTHER FROM SOUND SOURCE.   PODIUM BASE.  LIVING SPACE RAISED ABOVE STREET LEVEL  PARKING STRUCTURE OFTEN USED  STORAGE AND OTHER FUNCTIONS AT BASE BALCONIES & OVERHANGS.  BALCONIES WITH SOLID RAILINGS SHOULD BE USED IN FRONT OF WINDOWS (REDUCES SOUND TO INTERIOR BY 5 TO 10 DECIBELS).  ABSORPTION CAN BE IMPROVED IF THE BALCONY OVERHANG IS TREATED WITH SOUND ABSORBING MATERIAL.  BUILDING ORIENTATION.  COURTYARDS: • HARD-SURFACED PARALLEL WALLS CAUSE FLUTTER ECHOES WHICH INTENSIFY NOISE IN THE COURTYARD. • BY ANGLING OR STAGGERING THE BUILDINGS, NOISE BUILDUP CAN BE REDUCED. • KNOW THE FOLLOWING: O THE EFFECTS OF WIND AND TEMPERATURE ON SOUND PROPAGATION.   27  WIND:  DOWNWIND: INCREASE IN SOUND LEVEL. • DOWNWIND FROM THE SOURCE, SOUND IS NORMALLY BENT TOWARD THE GROUND INCREASING SOUND LEVEL.  UPWIND: DECREASE IN SOUND LEVEL. • UPWIND, SOUND IS BENT UPWARD CAUSING A SHADOW ZONE WHERE THE SOUND LEVEL WILL BE REDUCED.  EXAMPLE: • AT DISTANCES GREATER THAN 500 FEET, THE UPWIND MID-FREQUENCY ATTENUATION CAN BE ABOUT 10 DECIBELS FOR WINDS OF 10 MILES/HOUR. • A REVERSAL OF WIND DIRECTION CAN INCREASE THE SOUND LEVEL BY ABOUT 10 DECIBELS AT THE SAME LOCATION. • CONSEQUENTLY, DO NOT RELY ON ATTENUATION FROM THE WIND WHEN DESIGNING OUTDOOR NOISE CONTROL MEASURES.  TEMPERATURE.  ON A CLEAR, CALM DAY THE EFFECT OF TEMPERATURE GRADIENTS CAN CAUSE SOUND TO BEND UPWARD.  ON A CLEAR, CALM NIGHT, AIR TEMPERATURES ARE INVERTED CAUSING SOUND TO BEND TOWARD THE GROUND.  DIFFERENCE FROM DAY TO NIGHT CAN BE 10 DB FOR SOUNDS A 1000 FEET AWAY. O METHODS OF CONTROLLING HIGHWAY AND AIRCRAFT NOISE.  AIRCRAFT NOISE.  LAND-USE PATTERN: • SURROUND LANDING & TAKEOFF AREAS WITH INDUSTRIAL AND COMMERCIAL LAND USES, PROTECTING RESIDENTIAL PROPERTIES.  HIGHWAY NOISE:  METHODS OF CONTROL: • AVOID LOCATING OCCUPANCIES WITH 500 FEET OF HIGHWAY. • BERMS. • THIN-WALL BARRIERS. • ELEVATED & BELOW GRADE ROADBEDS. O ELEVATED ROADBED. O BELOW GRADE ROADBED. AESTHETICS • KNOW THE FOLLOWING: O EXAMPLES OF KEYNOTE SOUNDS, SIGNALS AND SOUNDMARKS.    KEYNOTE SOUNDS. 28  THOSE SOUNDS WHICH ARE HEARD BY A PARTICULAR SOCIETY CONTINUOUSLY OR FREQUENTLY ENOUGH TO FORM A BACKGROUND AGAINST WHICH OTHER SOUNDS ARE HEARD.  NORTHERN HINTERLAND: •  PRAIRIES: •  THE SOUNDS OF ICE AND SNOW BECOME KEYNOTE SOUNDS. THE SOUND OF THE WIND BECOMES A KEYNOTE SOUND. ELECTRONIC CULTURES: • TRANSFORMER HUM. • IN AMERICA PEOPLE TEND TO HUM IN B NATURAL WHICH IS ABOUT THE SAME FREQUENCY AS ALTERNATING CURRENT (60 CYCLES PER SECOND). • IN EUROPE PEOPLE HUM IN G SHARP WHICH IS ABOUT THE SAME AS EUROPEAN ELECTRICAL CURRENT (50 CYCLES PER SECOND)  SIGNALS.  FOREGROUND SOUNDS (LISTENED TO CONSCIOUSLY), GENERALLY THESE SOUNDS ARE LISTENED TO BECAUSE THEY GIVE SOME FORM OF ACOUSTIC WARNING.  A SOUND WITH A SPECIFIC MEANING, & IT OFTEN STIMULATES A DIRECT RESPONSE.   EXAMPLES: TELEPHONEBELLS, WHISTLES, HORNS & SIRENS. SOUNDMARKS.  THE TERM IS DERIVED FROM LANDMARK, & REFERS TO A COMMUNITY SOUND THAT IS UNIQUE OR POSSESSES QUALITIES WHICH MAKE IT SPECIALLY REGARDED OR NOTICED BY THE PEOPLE IN THAT COMMUNITY. O THE EFFECTS OF PITCH, AND REVERBERATION ON BUILDING ATMOSPHERE.  PITCH.    HIGH & LOW FREQUENCY • HIGH PITCH: COOLNESS • LOW PITCH: WARMTH ASCENDING & DESCENDING FREQUENCY MODULATION. • DESCENDING FREQUENCY: INDICATE BAD • ASCENDING FREQUENCY: HAPPY OR JOYFUL **REVERBERATION.   INTIMACY & MONUMENTALITY • LOW REVERBERATION: INTIMACY • HIGH REVERBERATION: MONUMENTALITY CONSCIOUSNESS OF SOUND. •   HIGH REVERBERATION: MORE SELF CONSCIOUS 29  ILLUSION OF PERMANENCE. • HIGH REVERBERATION: HARD SURFACES IMPLY PERMANENCE & VICE VERSA •  LOW REVERBERATION: SOFT SURFACES IMPLY IMPERMANENCE EFFECT ON TEMPO OF CONVERSATION. • HIGH REVERBERATION: SLOWS TEMPO (TALK SLOWER) • LOW REVERBERATION: SPEEDS TEMPO (TALK FASTER) O --WHAT MORPHOLOGY STUDIES OF THE SOUNDSCAPE HAVE DETERMINED.  STUDY OF THE CHANGING FORMS OF SOUND CHRONOLOGICALLY OR GEOGRAPHICALLY.  MATERIAL BASED CHANGES:  WOOD CULTURES. (EX JAPANESE) •  STONE CULTURES. (EX EUROPE) •      LOW FREQUENCY SOUND EMPHASIS HIGH FREQUENCY SOUND EMPHASIS CONCRETE, METAL & GLASS CULTURES. TRANSPORTATION BASED CHANGES:  FOOT TRAVEL.  WHEELED VEHICLES.  MOTORIZED VEHICLES. MORPHOLOGY OF SIGNAL SYSTEMS:  CHURCH BELLS.  FACTORY WHISTLE. 30