AKHILESH KUSHWAHA(16COMP021)TINKAL PATEL(16COMP022) JAY RAMI(16COMP023)DHRUTI BHATT(16COMP024) GUIDED BY: PROF. ANAND PANCHAL

VADODARA INSTITUTE OF ENGINEERING

ARCHITECTURAL ACOUSTICS

CONTENT INTRODUCTION CLASSIFICATION OF SOUND CLASSIFICATION OF AUDIABLE SOUND CHARACTERSTIC OF MUSICAL SOUND TYPES OF SOUND ABSORBING MATERIAL REVERBERATION,REVERBERATION TIME FACTOR AFFECTING ACOUSTIC OF BUILDING AND

THEIR REMIDIES CONDITION FOR GOOD ACOUSTIC

ARCHITECTURAL ACOUSTICS

INTRODUCTIONACOUSTICS IS A SCIENCE OF SOUND WHICH DEALS WITH THE PROPERTY OF SOUND WAVE,THEIR ORIGN,PROPAGATION AND THEIR OBSTACLES.

CLASSIFICATION OF SOUNDSOUND IS A VIBRATION IN ELASTIC MEDIUM WITH DEFINITE FREQUENCY AND INTENSITY WHICH CAN BE HEAR BY HUMAN EAR.ON THE BASIS OF FREQUENCY,SOUND ARE CLASSIFIED IN THREE TYPE:1.INFRASOUND.2.AUDIABLE SOUND. 3.ULTRASOUND.

INFRASOUNDINFRASOUND, SOMETIMES REFERRED TO AS LOW-FREQUENCY SOUND, IS SOUND THAT IS LOWER IN FREQUENCY THAN 20 HZ (HERTZ) OR CYCLES PER SECOND, THE "NORMAL" LIMIT OF HUMAN HEARING.

AUDIABLE SOUNDTHE SOUND WAVE HAVING FREQUENCY BETWEEN 20HZ TO 20KHZ ARE CALLED AUDIBLE SOUND

ULTRASOUNDTHE SOUND WAVE HAVING FREQUENCY GREATER THAN 20KHZ ARE CALLED ULTRASOUND

CLASSIFICATION OF AUDIABLE SOUND

THE AUDIABLE SOUND IS GENERALLY CLASSIFIED INTO TWO CATEGORY.1.MUSICAL SOUND2.NOISE

MUSICAL SOUND NOISE THE SOUND WHICH PRODUCE

PLEASING EFFECT TO OUR EAR IS CALLED MUSICAL SOUND.

THE WAVE FORM OF MUSICAL SOUND IS REGULAR.

IT DO NOT GOES IN SUDDEN CHANGE

EXAMPLES ARE,SOUND PRODUCE BY MUSICAL INSTRUMENT LIKE SITAR,VIOLEN,FLUTE,PIANO,ETC.

THE SOUND WHICH PRODUCE JARRING EFFECT AND UNPLEASENT TO HEAR IS CALLED NOISE.

THE WAVE FORM OF NOISE IS IRREGULAR .

IT GOES IN SUDDEN CHANGE EXAMPLES ARE,SOUND

PRODUCE BY FLYING AEROPLANE,ROAD TRAFFIC,CRACKERS,ETC.

CHARACTERSTICS OF MUSICAL SOUND

THE CHARACTERSTIC OF MUSICAL SOUND ARE:1.PITCH2.LOUDNESS3.TIMBRE

1.PITCHTHE QUALITY OF A SOUND GOVERNED BY THE RATE OF VIBRATIONS PRODUCING IT; THE DEGREE OF HIGHNESS OR LOWNESS OF A TONE.2.LOUDNESSLOUDNESS IS A DEGREE OF SENSATION PRODUCE ON EAR.LOUDNESS IS DEPEND UPON INTENSITY.3.TIMBREIT IS THE QUALITY OF SOUND WHICH ENABLE US TO DISTINGUISH BETWEEN TWO SOUND HAVING SAME LOUDNESS AND PITCH.

TYPES OF SOUND ABSORBING MATERIAL

THE SOUND ABSORBING MATERIALS ARE BROADLY CLASSIFIED INTO THE FOLLOWING FOUR CATEGORIES

(A) POROUS ABSORBENTS(B) CAVITY RESONATORS(C) RESONANT ABSORBENTS OR PANEL ABSORBERS(D) COMPOSITE ABSORBENTS.THE SPECIAL MATERIALS USED TO INCREASE THE ABSORPTION OF SOUND WAVES OR TO REDUCE THE REFLECTION OF SOUND WAVES IN A ROOM OR A HALL ARE KNOWN AS SOUND ABSORBING MATERIALS.

POROUS ABSORBENTWHEREVER SOUND WAVES STRIKE SURFACE OF A POROUS OF A MATERIAL, A PART OF SOUND WAVES GETS REFLECTED WHILE THE OTHER PART ENTER THE POROUS MATERIAL .THE PART OF REFLECTED WAVES ENERGY IS REDUCED WHILE , THE PART OF WAVES THAT ENTERED INTO THE POROUS MATERIAL IS CONVERTED INTO HEAT

CAVITY RESONATORWHEN SOUND WAVES ENTER THE RESONATOR; DUE TO MULTIPLE REFLECTIONS INSIDE , THE SOUND WAVES TO ARE ABSORBED .THE CAVITY RESONATOR MAY BE DESIGNED TO ABSORB SOUND OF ANY PARTICULAR FREQUENCY GENERATED BY MACHINES SUCH AS AIR CONDITIONER PLANT, MACHINES ETC.

RESONANT ABSORBENT OR PANEL ABSORBER

IN THIS SYSTEM , THE ABSORBENT MATERIAL IS FIXED ON A FRAMING WITH AN AIR SPACE BETWEEN THE FRAMING AND WALL.WHEN SOUND WAVES STRIKE THE PANEL, THEN DUE TO FLEXURAL VIBRATION OF PANEL , CERTAIN AMOUNT OF SOUND ENERGY IS ABSORBED BY THE PANEL WHICH IS CONVERTED INTO HEAT ENERGY.

COMPOSITE ABSORBERA COMPOSITE ABSORBER IS A SINGLE UNIT WHICH DOES THE FUNCTION OF THE OTHER THREE ABSORBERS MENTIONED ABOVE.THE COMPOSITE ABSORBER OF A PERFORATED PANEL FIXED OVER AN AIR SPACE CONTAINING POROUS ABSORBENT.THE PANEL MAY BE OF WOOD, PLYWOOD, HARD-BOARDS, PLASTER BOARD .WHEN SOUND WAVES STRIKE THE PANEL, THEY PASS THROUGH IT AND DAMPED BY RESONANCE OF THE AIR IN THE CAVITY.

REVERBERATION AND REVERBERATION TIME

REVERBERATION THE PERSISTENCE OR PROLONGATION OF

SOUND IN HALL EVEN THROUGH THE SOURCE OF SOUND IS CUT OFF IS CALLED REVERBERATION. REVERBERATION TIME

THE TIME TAKEN BY THE SOUND TO FALL BELOW THE MINIMUM AUDIBILITY LEVEL AFTER THE SOURCE STOPPED SOUNDING IS CALLED REVERBERATION TIME.

FACTORS AFFECTING ACOUSTICS OF BUILDINGS AND THEIR REMEDIES REVERBERATION TIME: REVERBERATION IS THE

PERSISTENCE OR PROLONGATION OF SOUND IN HALL EVEN AFTER THE SOURCE STOPPED EMITTING SOUND.

THE REVERBERATION TIME IS TAKEN BY THE SOUND TO FALL BELOW THE MINIMUM AUDIBILITY LEVEL.

IN ORDER TO HAVE A GOOD ACOUSTICS EFFECT, THE REVERBERATION TIME HAS TO BE MAINTAINED AT OPTIMUM VALUE. THE REASON IS , IF THE REVERBERATION TIME IS TOO SMALL, THE LOUDNESS BECOMES INADEQUATE. AS A RESULT THE SOUND MAY NOT REACH TO LISTENER. THUS ,THIS GIVES THE HALL A DEAD EFFECT.

REMEDIESTHE REVERBERATION TIME CAN BE MAINTAINED AT OPTIMUM VALUE BY ADOPTING THE FOLLOWINGS WAYS.1 BY PROVIDING WINDOWS AND OPENINGS. 2 BY HAVING FULL CAPACITY OF AUDIENCE IN A HALL OR ROOM.3 BY USING HEAVY CURTAINS WITH FOLDS.4 BY COVERING THE FLOOR WITH CARPETS.5 BY DECORATING THE WALL WITH BEAUTIFUL PICTURES, MAPS, ETC.

LOUDNESS THE UNIFORM DISTRIBUTION OF

LOUDNESS IN A HALL OR A ROOM IS AN IMPORTANT FACTOR FOR SATISFACTORY HEARING. SOMETIMES, THE LOUDNESS MAY GET REDUCED DUE TO EXCESS OF SOUND ABSORBING MATERIALS USED INSIDE A HALL ROOM.

REMEDIES1 BY USING SUITABLE ABSORBENTS AT PLACES WHERE NOISE IS HIGH. AS A RESULT, THE DISTRIBUTION OF LOUDNESS MAY BECOME UNIFORM.2 BY CONSTRUCTING LOW CEILINGS FOR THE REFLECTION OF SOUND TOWARDS THE LISTENER.3 BY USING PUBLIC ADDRESS SYSTEM LIKE LOUDSPEAKERS

Focusing and Interference EffectsTHE PRESENCE OF ANY CONCAVE SURFACE OR ANY OTHER CURVED SURFACE IN A HALL MAY MAKE THE SOUND TO BE CONCENTRATED AT THIS FOCUS REGION. AS A RESULT, THE SOUND MAY NOT BE HEARD AT ALL AT OTHER REGIONS. THESE REGIONS ARE REFERRED AS DEAD SPACE HENCE , SUCH SURFACES MUST BE AVOIDED.IN ADDITION TO FOCUSSING THERE SHOULD NOT BE INTERFERENCE OF DIRECT AND REFLECTED WAVES. THIS IS BECAUSE, CONSTRUCTIVE INTERFERENCE MAY PRODUCE A SOUND OF MAXIMUM INTENSITY IN SOME PLACES AND A DESTRUCTIVE INTERFERENCE MAY PRODUCE A SOUND OF MINIMUM INTENSITY IN OTHER PLACES. THUS ,THERE WILL BE AN UNEVEN DISTRIBUTION OF SOUND INTENSITY.

REMEDYCURVED SURFACES CAN BE AVOIDED. IF CURVED SURFACES ARE PRESENT, THEY SHOULD BE COVERED WITH SUITABLE SOUND-ABSORBING MATERIALS.

ECHOAN ECHO IS HEARD DUE TO REFLECTION OF SOUND FROM A DISTANT SOUND-REFLECTING OBJECT.IF THE TIME INTERVAL BETWEEN THE DIRECT SOUND AND REFLECTED SOUND IS LESS THAN 1/15TH OF A SECOND , THE REFLECTED SOUND IS HELPFUL IN INCREASING THE LOUDNESS. BUT ,THOSE SOUNDS ARRIVING LATER THAN THIS CAUSE CONFUSION.

REMEDYAN ECHO CAN BE AVOIDED BY COVERING LONG-DISTANCE WALLS AND HIGH CEILING WITH SUITABLE SOUND-ABSORBING MATERIAL. THIS PREVENTS REFLECTION OF SOUND.

ECHELON EFFECTIT REFERS TO THE GENERATION OF A NEW SEPARATE SOUND DUE TO MULTIPLE ECHOS. A SET OF RAILINGS OR ANY REGULAR REFLECTING SURFACE IS SAID TO PRODUCE THE ECHELON EFFECT. THIS ECHELON EFFECT AFFECT THE QUALITY OF THE ORIGINAL SOUND.

REMEDYTHE REMEDY TO AVOID ECHELON EFFECT IS TO COVER SUCH SURFACES WITH SOUND-ABSORBING MATERIAS.

RESONANCEResonance occurs due to the matching of frequency. If the window panels and sections of wooden portions have not been tightly fitted, they may start vibrating, thereby creating an extra sound in addition to the sound produced in the hall.

REMEDYThe resonance may be avoided by fixing the window panels properly, Any other vibrating object which may produce resonance can be placed over a suitable sound-absorbing material.

NOISETHE UNWANTED SOUND IS CALLED NOISE . THERE ARE THREE TYPES OF NOISES.1 AIR-BONE NOISE2 STRUCTURE-BONE NOISE3 INSIDE NOISE

CONDITION FOR GOOD ACOUSTICS1.THE QUALITY OF THE SPEECH AND THE MUSIC REMAINS UNCHANGED IN EACH AND EVERY PORTION OF THE HALL.2.THE SOUND PRODUCED MUST BE SUFFICIENTLY LOUD.3.THERE SHOULDN’T BE ANY ECHO.4.THE REVERBERATION SHOULD BE PROPER.5.THERE SHOULD NOT BE ANY FOCUSING OF SOUND IN ANY PART OF THE HALL.6.THE WALLS SHOULD BE SOUND PROOF TO AVOID THE EXTERNAL NOISE IN THE HALL.

THANKYOU