Acoustic Evaluation Of Vernacular School Buildings In Kerala
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-551833Acoustic Evaluation of Vernacular SchoolBuildings in KeralaJolly JohnDr. Ashalatha ThampuramDepartment of ArchitectureTKM College of EngineeringKollam, Kerala, Indiajollyjkollam@gmail.comDean, Mohandas College ofEngineeringKerala, IndiaAbstract—This paper aims at an acoustical evaluation ofVernacular school buildings in Kollam. The two acousticparameters, background noise levels and reverberationtime has been studied and measured scientifically to assessthe quality of learning environment. The measured valueswere compared to the acoustical recommendations ofIndian standards. The study of one of the schools ispresented in detail. The finding of the study reveals thelack of acoustic comfort in school environments especiallyin classrooms and points out the need for intervention.Dr. B PremletProfessor, TKM College ofEngineeringKerala, Indiaconsuming their cognitive abilities which could be betteremployed in paying attention to understanding the content oftheir classes. A medical report in U.S. reveals that 12.5% ofschool aged children has hearing loss caused by excessivenoise. The survey conducted showed that 32% of the teachersreported having occasional voice fatigue and 20% have missedwork due to voice problems. It has been observed that onlyvery little studies related to acoustic comfort in classrooms hasbeen reported in India [12].The goal of this paper is to summarize the fieldmeasurements of the acoustical parameters (background noise,reverberation,) carried out in Vernacular school buildings inKerala. Efforts have been made to assess the acousticalefficiency of vernacular classrooms and compare the samewith stipulated sticcomfort;background noise; Reverberation time (RT); Decibel (dB)I. INTRODUCTIONA.Educational ScenarioVernacular school architecture categorizes methods ofconstructions which use locally available resources andtraditions to address local needs. The vernacular architectureof Kerala is known for its use of natural and passive methodsfor a comfortable indoor environment [1]. The orientation ofbuildings, internal arrangement of spaces, presence ofcourtyard, use of locally available materials and methods ofconstructions have contributed to the overall quality of theenvironment. Timber is the prime structural material used forcolumns, roof frames. The long steep sloping roofs built toprotect the wall and withstand heavy monsoon rains give thedistinctive visual form. Studies on Kerala vernacularbuildings, related to wind flow, thermal comfort, energyefficiency and vastushastram, has been reported by researchers[2-4]. However, only limited information is availableregarding acoustic comfort in vernacular buildings in mmunication between teachers and students and amongstudents. The efficiency of the learning environment dependslargely on the measure of the acoustic conditions of the school[5]. Children spend 12% of their effective time in schools. Theacoustic comfort parameters (ambient noise levels,reverberation time, sound insulation, speech intelligibility andacoustical materials) in classrooms have been the focus ofseveral studies in different countries of the world [5-11]. Highlevels of noise in school makes students prematurely tired,The education scenario in Kerala is well advanced whencompared to other states in India. As per the census 2011, theeffective literacy rate is 93.6% [13]. There are 12,644 schools(Government/aided) in addition to the schools in privatesector. In the past, school environments were silent andpleasant. Today the increased urbanization has deteriorated theacoustic environment of schools by making them relativelymore noisy and reverberative. The total number of studentpopulation (age group 14-18) is 4.4 million which amounts toth1/8 of the total population of Kerala [14]. Thereforeaddressing any issue related to student population has verystrong impact in the state.B.Influence of ClimateKerala located in the south west coast of India has acharacteristic tropical humid climate because of its geographicsetting [15]. In this type of climate, buildings have openelongate plan shape with a single row of rooms to allow crossventilation. All the evaluated school buildings haveclassrooms arranged along a corridor allowing crossventilation Fig.1. This arrangement ensures thermal comfort,however there will be conflict between thermal and auralrequirements in humid climates where the buildings requireIJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-5518openings; therefore it cannot effectively control noisepenetration.IV.34RESULT AND OBSERVATIONSA. Location with respect to roadThe primary survey revealed that 52.6% of schoolsare located adjacent to main roads while 47.4% of the schoolsare located in areas which do not have bus access and can beapproached only by private vehicles.B. Layout of building blocks and building typesFig. 1. Layout of Eravipuram Government school at Thattamala, Kollam.C. Regulations on School Building designIn Kerala, the design and construction of schoolbuilding is regulated by the Kerala Building Rules (KBR)[16]which set forth standards for the functional design. The onlyregulation specified and can be related to acoustic comfort isthe minimum distance of 6 meters between roadway andschool. The broad recommendations for providing acousticcomfort in school buildings given in the National buildingcode of India (NBC-2007)[17] are mentioned later in thispaper.The study revealed that there was no organized pattern ofarrangement of building blocks within the site. In most of theschools the building blocks were constructed in many phasesat different periods, depending on the necessity of additionalarea requirement and were placed in the space available withinthe school site. However two predominant building types wereidentified, a) vernacular building blocks Fig.2a, and b)modern building blocks Fig.2b. It was also observed that in73.3% of the surveyed schools, new construction activitieshave been initiated by building new blocks or by replacing theexisting vernacular old buildingsII. STUDY AREAIJSERThe evaluated schools are located in Kollam educationdistrict of Kerala state in India. Some of them are located innoisy areas as they abut main roads, while others are locatedin areas which are relatively quiet and can be approached onlyby private vehicles.III. METHOD OF STUDYA. Prelimanary investigationThe study was carried out by collecting primary datathrough observations, interviews, questionnaire survey andtaking onsite reading. 30 Government High Schools/HigherSecondary Schools in the Kollam education district wereidentified, and an overall physical survey was carried out. Thesurveyed schools were attended by children from class V toclass XII. (age 11-18years). General information on thepositioning of school buildings with respect to road, buildingtype, layout of class rooms, classroom area, and classroomvolume was collected. On site measurement was carried outby recording the ambient background noise levels outside andinside all the school compounds. The ambient noise levelsinside furnished classrooms of each school were measured.Two situations were considered for taking the measurement inthe classrooms. 1) all windows open in order to obtain theactual noise level in classroom. 2) all windows closed to verifythe noise reduction provided by the existing windows. TheReverberation time inside unoccupied furnished classrooms inall the schools was recorded. All measurements were taken ondays without any typical noises such as rain, thunder or strongwinds.Fig. 2a. Vernacular buildingFig. 2b. Modern buildingVernacular school buildings of Kerala are characterizedby the humble scale, merging with nature. The longcolonnaded corridors, steep sloping tiled roofs and projectingeaves are evolved from the climatic consideration. Thebuildings are either single or double storied as shown in Fig.3.Most of them are made of brick masonry walls, plastered withlime mortar and lime washed. Very few buildings have lateriteor stone masonry walls. The roof frame consists of woodenrafters supported on wall plate and ridge. The reapers are fixedon the rafters and covered with mangalore tiles. The flooringis of lime concrete, finished with clay tiles.Fig. 3. Single and doubled storied vernacular school buildingsIJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-5518C. Layout of classrooms35The recommended limit of background noise for classrooms,in different countries are shown in Table 3 [20].The vernacular school plans were classified according tothe arrangement of classrooms along the corridor, andaccordingly three predominant types of plans were identifiedas shown in Table.1.TABLE 2. RECORDED VALUES OF SOUND LEVELS IN SCHOOL ENVIRONMENTSAND CLASSROOMSAverage noise levelsSCHOOLTABLE I. TYPE OF ARRANGEMENT OF CLASSROOMS ALONG 371.7S482.3S5S6CORRIDORFig.4. gives the percentage of building blocks in each 1.48TABLE 3. RECOMMENDED SOUND LEVELS FOR CLASSROOMS IN DIFFERENTCOUNTRIESCountryNoise descriptorBrazilFranceGermanyUSAaIndiaLAeqYear of definitionIJSERFig.5. Percentage of buildings in each categoryD. Sound levels in vernacular school environments andclassroomsThe measured average background noise levels in 10vernacular school environments abutting major roads, and theaverage sound levels in the classrooms are given in Table.2. Inmost of the countries, noise regulation suggests that themaximum outdoor noise level for education buildings shouldbe 55dB (LAeq)[18].The measured sound levels werecompared to the comfort and acceptability parameters ofNational Building Code of India, which states the maximumcomfort range of 40-45dB(LAeq) for classrooms[19].Classroom 45――aNational Building Code of India 2007The average background noise measured inside allthe school environs was higher than the recommendednational standards (LAeq55dB). The background noise ismainly contributed by the traffic noise abutting the schoolcompound and absence of proper noise barriers for noiseattenuation.It was observed that the average background noiselevel in all classrooms (with windows in open and closedpositions), are higher than the recommended nationalstandards. Noise from the adjoining classrooms, studentsplaying in the open spaces, voice of the teacher taking class inthe nearby class room, traffic noise in case of classroom closeto roads and footsteps of students were the main contributorsof high noise levels.The measured average background noise levels and soundlevels inside unoccupied classrooms with the recommendedlimits are shown in Fig.5.IJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-55183690Background noise level outside theschoolSound levels in decibels(dB)807060Background noise level inside theschool50Sound level inside unoccupiedclassrooms40Recommended noise level on roadsabutting school (70dB)3020Recommended noise level in schoolcompounds (55dB)10Recommended soundlevel insideclassrooms (45dB)0S1S2S3S4S5S6S7S8S9S10schoolsIJSERFig. 6. Sound levels measured in 10 vernacular schools along with the recommended values.E. Reverberation TimeTABLE. 4 RECOMMENDED REVERBERATION TIME IN CLASSROOMS INReverberation time is an important parameter thatinterferes with the acoustical quality of a classroom. It isdependent on volume of room, sound frequency and the totalabsorption in the room. Table. 2 also lists the RT measured inunoccupied furnished class rooms of the above ten schools.According to the National Building Code of India-2007 theacceptable RT for classroom is 0.75-1.2 seconds. Theestablished recommended reverberation time of classrooms indifferent countries are shown in Table. 4.The measured RT values are within therecommended limits in 60% of the classrooms. In most of theschools long halls were divided into two or three classroomsby partition walls which were not built to the roof height.These openings above the walls increased the total absorptionin classrooms, resulting in the reduction of RT. Highreverberation time in remaining classrooms indicates the lackof absorbing materials inside the class room resulting in pooracoustical quality. Reverberating environments reduces theconcentrating ability and speech intelligibility, forcing theteacher to speak louder. Increased RT also increases thebackground noise in the rooms.DIFFERENT z)Volume (cubic meter)Brazil0.5 - 0.7270 V 600France0.4 – 0.80.6 – 1.2V 250V 250Germany0.6 – 1.0250 V 750USA0.60.7V 283283 V 566India a0.75-1.2500-0.75-1.2aNational Building Code of India 2007Equipment and softwareThe study was conducted using the equipment andsoftware from Bruel and Kjaer. The sound level meter BK2250, sound amplifier BK 2716, sound source BK 4292 wereused for the measurement of sound levels and reverberationtime. The building qualifier BK7831, utility software BK5503,frequency analysis software BK 7223,and RT software BK7228 were used for the analysis.IJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-551837IJSERFig.7. Layout of Eravipuram Government school at Thattamala, KollamV. CASE STUDYThe Eravipuram Government High school located atThattamala, in Kollam education district, abuts the Nationalhighway-47. The school layout is shown in Fig.6. It has astrength of 1200 students with 53 teachers. The school hasthree blocks; primary, high school and higher secondaryblock. The high school block is single storied vernacularbuilding and has classrooms arranged along a 1.9 meter widecorridor in a U‘ shape. The classrooms have windows alongthe corridor and on the opposite side, promoting good crossventilation suitable for the warm humid climate of Kerala. Thewalls are 35 cm thick built with brick masonry plastered withlime mortar. The flooring is of cement concrete, finishedcement plaster. The inclined roof made of timber frames issupported on masonry walls and timber columns along thecorridor, with mangalore tiles laid above it. This is one of thetypical layouts of vernacular school design seen in Kerala.A. Background noise in schoolenvironments andclassroomsTo evaluate the acoustic composition of the schoolenvironment, the continuous equivalent sound levels weretaken at different locations within the school compound. Thenoise contour map of the school environment was prepared toinvestigate the noise condition and acoustic suitability ofpositioning of school building in the site, as shown in Fig. 7.Fig.8. Acoustic evaluation of schoolThe methodology of noise mapping in built up areasby measuring the noise levels on a grid system was adoptedIJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-5518[21]. The contours were categorized at 3 dB interval on ahorizontal plane. The barrier attenuation offered by thecompound wall with respect to distance was measured. Asection indicating the noise levels with respect to distance isshown in Fig.8.38High noise level was recorded at the center of the courtyard.The arrangement of classrooms around an open courtyarddirectly facing the road confined the traffic noise, causing abuildup of sound energy [22]. The low height of thecompound wall offered very less noise reduction. The isolatedtrees near the wall did not provide any acoustical shielding.Fig.9. Low barrier attenuation offered by compound wallA detailed investigation was made on the internal ambientnoise levels in all classrooms. The mean sound levels werecalculated for each room. The sound spectrum of themaximum sound levels at different positions wassuperimposed on the family of Noise Criteria (NC) Curves andthe single value of NC Curve was obtained. The obtainedcurves were compared to the acceptability parameter whichestablishes the range NC35- NC40 as the NC curve forcomfort in classrooms. The NC obtained for noise level of aclassroom and corridor is shown in Fig.9. The frequencyanalysis of the measured sound levels in classroom, corridors,outside and inside the school compound was carried out toidentify the frequency which had the maximum sound levels.It was observed that the noise levels exceeded thelimit of 40-45 dB determined by the standards in all cases.Noise levels above 60dB exceed the normal speaking voicelevel by 5 dB, impairing the listener‘s attenuation [23]. Thesound level measurement taken during the class hour was64.5dB indicating the stress on the vocal chords of teachersresulting in fatigue. With regards to the sound levels listed inthe Table.5, it can be concluded that the classrooms are notcomfortable acoustically. In addition to the traffic noise, thenoise from the play area located centrally contributed to theincrease of sound level inside the classroom. It was alsoobserved that walls of few classrooms were not constructed tothe full height. The noise and the voice of the teacher from theadjacent classrooms interfered with the normal functioning ofthe classrooms.IJSERTABLE 5. SUMMARY OF NOISE LEVELS IN CLASSROOMS.Sound levels in decibelsOccupied classroomsNoise CriteriaCurvesWindows open66.755Windows closedInside classroom with teacher speaking59.864.54550Inside classroom with students in silence60.150In empty classroom with classes going on in adjacent upiedclassroomsWhile classrooms areoccupiedIJSER 2015http://www.ijser.orgRecommendedNC CurveNC35-NC40
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-551839120100NR 75NR 70NR 65Sound levels in dB80NR60NR 55NR 5060NR 45NR 4040NR 35NR 30NR 2520corridoorclassroomNR 28031.563125250500100020004000 8000Frequency in HzIJSERFig.10. Sound spectrum of corridoor and a classroom superimposed on NC curves.Fig.11. Detail drawing of aclassroom.B. Measurement of Reverberation TimeSummary of the reverberation time measured in 5 classroomsat 1000 Hertz frequency, along with the classroom dimensionsare shown in Table 6. The classrooms are built without anyacoustical treatment. The openings above the walls in theseclassrooms increased the total absorption resulting in low RT.The lack of absorbing materials inside the classrooms wasevident in classrooms where the opening above the wall wasclosed.TABLE. 6. TYPE OF ARRANGEMENT OF CLASSROOMS ALONG THE 55.965.9735.58167.041.92C. Measurement of sound insulationThe methodology specified in National Building Code ofIndia Section-4 (Specification of sound insulation) wasadopted for the measurement of sound insulation. Thestandardized level difference, referred as Dnt‘ which specifiesthe sound insulation between rooms was calculated for thewall between classrooms and the wall separating theclassroom and corridor. The ‗Dnt‘ was compared with theminimum recommended sound reduction.The calculated standardized level difference Dnt ofclassroom was 20.6dB. This is low when compared to therecommended minimum sound reduction of 35 dB betweenclassrooms. The recommended minimum sound insulation forwalls separating classroom and corridor is also 35 dB, but themeasured value is only 28.8dB. The low values contributesignificantly to the noise transmission between the classroomsand from the corridor.IJSER 2015http://www.ijser.org
International Journal of Scientific & Engineering Research, Volume 5, Issue 7, July-2014ISSN 2229-5518VI. CONCLUSION40ReferencesThe present study, which is the first of its kind inKerala, evaluated the acoustic parameters-background noiseand RT in 10 vernacular schools located in Kollam district.The measured background noise and RT are compared withthe recommended values prescribed by Indian standards andwas found high. The findings support the strong need toenforce regulations in Kerala building rules to meet theacoustic comfort standards in schools. The planners have animportant role while preparing the Master plan to ensure thatareas under educational use are zoned in relatively quiet areas.The detailed investigation proved that the classroomsin vernacular schools are not acoustically comfortable. Thehigh background noise in classrooms was mainly due to theintrusion of noise through the openings and poor insulation ofmaterials used. The design layout of the school which enclosesa courtyard space confined the traffic noise increased the noisebuildup. A preferred layout would be to locate the courtyardsuch that the building shields the traffic noises. Low acousticalinsulation of walls and lack of good absorbing materials insidethe classrooms increased the RT in classrooms. The design ofschool investigated is one of the typical designs popularly seenin many regions of the state. Thus the acoustic deficiencies arelikely to be repeated, impairing the acoustic comfort of a largestudent population of the state. Achieving acousticallycomfortable environment in schools through the use ofappropriate materials will increases the efficiency and thephysiological well-being of the students and teachers. Thestudy strongly support the need for intervention by architectsand designers at the initial stages of designing the layout andchoosing of appropriate building materials which are moreabsorptive, especially in classrooms to achieve an acousticallyconducive environment for learning.[1]A.S.Dili, M.A.Naseer, T.Zacharia Varghese, ―Passive control methodsfor a comfortable indoor environment Comparative investigation ofTraditional and modern architecture of Kerala in summer,ǁ Energy andBuilding, 2011, pp.653-664.[2]S.Edward Kurian, ― Thermal performance of traditional buildings inKerala,ǁ The Journal of Indian Institute of Architects, 2008, pp.7-9.[3][4]Ashalatha Thampuran, Balagopalan T.S. Prabhu, ―Nallukkettus ofKeralaǁ, The Journal of Indian Institute of Architects, 1993, pp.2-8.Luban D Sutherland,ǁGood classroom acoustics is a good investment. InInternational congresson acoustics ICA,ǁ Rome, Italy, 2001,Proceedings[5]S.K.Tang, ―Speech releated acoustical parameters in classrooms andtheir relationshipsǁ, Applies Acoustisc,2008,Vol.69, pp.13188-1331.[6]CA Mydlarz, R Conetta, D Connolly, TJ Cox, JE Dockrell, BM Shield,―Comparision of environment acoustic factors in occupied schoolclassrooms for 11-16 year old students,ǁ Building and Environment,2013, Vol. 60, pp. 265-271.[7]E.L.Kruger, PHT Zannin, ―Acoustic, thermal and luminous comfort inclassrooms,ǁ Building and Environment, 2004, Vol.39, pp.1055-1063.P.H.T.Zannin, Marcon CR, ―Obective and Subjective evaluation ofacoustic comfort in classrooms,ǁ Applied Ergonomics, 2007, Vol.38,pp.675-680.[9] Nithya Banukumar, A.Ramachandriah ―Subjective Assessment ofListening environmentsin University classroomsǁ,Internationalconference, IIT Madras, India, Feb 2013, Proceedings.[10] VA Collect da Graca, DCCK Kowaltowski, JRD Petreche, ― Anevaluation method for school building design at thepreliminaryphase with optimization of aspects of environmental comfortfor theschool system of the State Sao Paulo in Brazilǁ, Building andEnvironment, 2007, Vol.42, pp.984- 999.[8]IJSERAcknowledgmentThe authors would like to thank the department ofArchitecture, TKM College of Engineering for providing theequipment in the department, and Kerala State Council forScience, Technology, and Engineering ( KSCSTE) for thefinancialsupportinconductingthisstudy.[11] Carl C.Crandell, Joseph J, Smaldino, ―Classroom Acoustic for childrenwith normal hearing and with hearing impairment Language, speech andhearing services in schoolǁ, Oct 2000, Vol.3, pp.362-370.[12] G Muthu Shoba Mohan, ―Acoustical criteria for a better learningenvironment in classroomsǁ, International conference, IIT Madras, India,Feb 2013, Proceedings.[13] Census data of India – 2011, census.india.gov.in.[14] www.education.kerala.gov.in.[15] Koenigsberger, Ingersoil, Mayhew, Szokolay, ― Manual of TropicalHousing and Building- Climate design. Indiaǁ. Orient Longman Ltd ,2001.th[16] Kerala Municipality Building Rule -1999, 15 edition[17] National Building Code of India 2007. Bureau of Indian Standards. NewDelhi.[18] Bruel and Kjaer, Measurements in Building Acoustics,2006,www.bk.dk.[19] Lawrence E. Kinsler, Austin R Frey, Allen B. Coppens, JamesthSandens, ― Fundamentals of Acousticǁ, 4 ed. John Wiley & Sons,2000.[20] Building Bulletin -93 UK, Acoustic Design of schools – a design guide.[21] Selma Kurra, Levent Dal, ― Sound insulation design by using noisemapsǁ, Building and Environment, 2012, Vol.49, pp.219-303.[22] M. David Egan, Architectural Acoustic. J. Ross publishing, 2008.[23] Paulo H.T.Zannin, Daniele Petri Zanardo Zwirtes, ―Evaluation ofacoustic performance of classrooms in public schools. AppliedAcoustics,ǁ 2007, Vol.70, pp. 626-635.IJSER 2015http://www.ijser.org
Jolly John Dr. Ashalatha Thampuram Dr. B Premlet Department of Architecture Dean, Mohandas College of Professor, TKM College of TKM College of Engineering Engineering Engineering Kollam, Kerala, India Kerala, India Kerala, India jollyjkollam@gmail.co
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