Acoustic Wall[1]

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ACOUSTIC WALL

SOUND CONTROL INBUILDINGS


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WALLS FOR PRODUCTION STAGE AT FILM STUDIO


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SASANI STUDIOS

Sasani Studios, a one-stop filmtelevision and multimedia post-production company of internationalrepute, appointed dhk Architects todesign and build their productionfacilities in Cape Town. The

soundproofing and structuralrequirements had to conform to thehighest standards.

The dynamic, young firm of architects turned an existing warehouse atthe Cape Town Waterfront into a highly successful Sasani Studioswith three production stages - 1143 m, 840 m and 425 m - meeting

all required international standards.

The main structure consisted of two skins of sound-absorbent walling- an external wall and an internal wall. Party walls were also speciallydesigned to be soundproof. With the experience and advice of theConcrete Manufacturers Association, modular, fluted, split-face 90mm blocks were used in two back-to back leaves to form a 190mmparty wall up to 12,4 metres high.

The structure of these tall walls was designed by consulting engineersHenry Fagan & Partners. They chose 400 x 400mm pilaster blocks toform the reinforcing columns. The pilaster block is specially designedto intersect with the masonry infill panels and provide sufficient core

cavity for reinforcement and concrete.

The choice of absorbent and sound-reducing concrete masonrymanufactured by Columbia DCM was based on previous experiencewith this product, which was researched and developed by theUniversity of Cape Town Acoustic Department. Readily availablematerial and simple masonry construction provided a quick solutionwithin a tight timetable.

The internal wall was constructed with modular 140mm fluted, split-face concrete blocks up to a height of 2,6 metres. Above this,extending to the ceiling, was a sound-absorbent panel - a dry-wallpartition to which a sound-absorbent polyester blanket was fixed with

chicken wire mesh.

The criteriaThe studios were designed to meet these

requirements:! Airborne sound reduction from 80dBA to below

30dBA! Reverberation time: 1,5 seconds! Dead space internally - NR25 - requiring cavity

walling! Limiting noise penetration and leakage areas

particularly from the roof structure

An in ternal 2,6 metre base wal l, and above it , a sound-absorbent polyester blanket fitted against the dry wallwhich extends to the ceiling.

Appo inted archi tects :dhk Achitects, Cape Town Tel: (021) 4618151


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SASANI STUDIOS

a filmset in one of the studiosThe cavity between the ceiling and the roof sheets was filledwith a mineral wool layer with another layer on the underside.All penetration points in the roof sheeting and ceiling werecarefully sealed airtight in order to prevent air-borne soundtransmission from outside.

These high roof-loading requirements were met bystrengthening the members and connections of theexisting trusses as well as supporting the trusses atmid-span on steel girders, spanning the length of theproduction stages and inserted between the apex andbottom truss chords.

While the stages were soundproofed, the existing steel roofstructure had to be upgraded to support the increased load

requirements, which were:! 45kg/m2 for soundproofing materials! 80kg/m2 for the lighting requirements of the filmsets! Dead loads of a new gantry walkway system as well

as associated live loads. The walkways comprise amain or central walkway extending over the length ofthe production stages with secondary gantriesbranching off towards the sides.

! Dead load of a grid of steel scaffold pipes forsupporting lights.

! Steel I-beams fixed to the lower truss chords acting astracks for 1 tonne chain blocks.

The offices with a communal meeting area in the

foreground


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CAPE TECHNIKON CAMPUS DEVELOPMENT

Harris & Harris Architects

Tel: (021) 426 1731Consulting engineers:KFD Wilkinson (Pty) LtdTel: (021) 425 1610 and

Liebenberg & StanderTel: (021) 421 2430

The former consortium of Colyn & Meiring/Interplan, nowHarris & Harris Architects, Cape Town, investigated concretemasonry single-leaf M140 split-face for all internal walls of the

Cape Technikon. The University of Cape Town AcousticDepartment, under Prof. AT Semmelink in co-operation withColumbia DCM, conducted intensive research to findoptimum masonry performance in respect of airborne soundabsorption and sound reverberation for classrooms. Manyalternative mix designs and density tests were carried out toachieve desired standards of performance. The outcome wasto provide excellent acoustic performances with unrenderedfacing blocks in standard classrooms and large and smalllecture theatres for 140 and 250 students. The photographsillustrate some of the applications and workmanship.


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HOLIDAY INN GARDEN COURT

Consulting engineers:Liebenberg & StanderTel: (021) 421 2430Contractors: WBHO Construction (Pty) LtdTel: (021) 794 1300

In the early 1980s the nine-storey CapeTown headquarters of Shell Africa wasto be converted into a centrally situatedhotel. The investigating engineersconsidered that the additional loading ofthe structure with extensive internal

walls was critical. They requiredmaximum sound reduction with minimummass and cost. Plastered concretemasonry was thought to be the solution.However, little reliable information wasavailable on the acoustic performance ofmodular 90mm masonry units.

The University of Cape Town, under theleadership of Prof. AT Semmelink in co-operation with Columbia DCM,conducted research on behalf of theclient. Progressive tests were conductedon each of the following unplastered,

one-sided plastered, two-sided 12mmplastered and, finally, two-sidedplastered and painted walls. The resultswere most effective, exceeding theminimum sound reduction requirementsfor party walls in the hotel environment.The photograph shows the extensivesize of the hotel.


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CONCRETE MASONRY FOR SOUND INSULATIONAND SOUND REDUCTION

The National Building Regulations do not deal with acousticperformance criteria for buildings. While noise control of airbornesound (external or internal) in buildings is dependent on a host ofvariables, it can be said that dense concrete masonry for external

walling and party walls have generally been accepted as highlysuitable material.

Resistance to sound transmission increases not only with wallthickness but more so with increasing mass of a masonry wall. Insingle-leaf walling, density of the masonry unit and surface texturemost certainly effect the sound absorption and/or soundtransmission through a wall. "Diaphragm walls, however, becauseof the large internal void, possess better prospects for both soundand thermal insulation." (Structural Masonry Design Manual by WGCurtain page 263).

Most available literature leans heavily on British codes and

regulations such as Bs 2750: 1956, which provides tables ofperformance standards against which a construction can be tested.During 1972 a leading British manufacturer, Fortecrete DCM, hadtests carried out by the research organisation AIRO in accordancewith BS 2750:56. The results are shown in our table for variousthicknesses of masonry blocks.

Sound level in decibels

Typical home sound levels

This chart shows the decibles of sound radiated bymany of the typical noise sources in the modernworld and how much reduction in decibels isnecessary to bring about tolerable, quiet conditionssuitable for a home environment.


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The frequency range (Hz) 100 to 3150 was used in thetests and is reflected for three basic widths of denseconcrete masonry (ie. M90mm, M140mm and M190mm).For good reasons, the masonry manuals, engineering

literature and design guides deal only in general terms withthe subject. Specific applications and requirements need tobe tested separately against the masonry available in aregion. In the examples shown in this publication,designers all investigated the specific performance of themasonry available. Density, surface texture, porosity andspecific material grading all affect the acoustic value of themasonry and cannot be generalised.

For example, detailed material composition research wascarried out for the Cape Technikon's extensive internalwalling. Finally, six different masonry-mix designs weretested and one eventually turned out to provide optimum

performance for sound insulation and reverberation of fair-face, unrendered, large-scale masonry application. Theaesthetic appearance of the masonry illustrated in thispublication was not compromised.

Acknowledgements to Gunter Koch, now acting as CMARegional Representetive of the Western Cape, for hiscontribution to acoustic wall research.


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Head Offi cePO Box 168 Halfway House 1685Tel: +27118056742Fax: +27113154683Email: [email protected]:http://www.cma.org.za

Western Cape Regional Office:GR KochPO Box 7231, Roggebaai,

Cape Town 8012Tel:/Fax: +27214612511Cell: 0824547657Email: [email protected]

Concrete Manufacturers Ass ociation - Membership Lis t (Masonry) 2001/2002

Cape Brick (021)5112006 Morula Brick & Sand (Pty) Ltd* (012)5491727

Concor Technicrete (Pty) Ltd * (011)4952200 Neat Contech cc* (046)6481359

Corobrik (Pty) Ltd* (031)5603911Precast Concrete Industries(Namibia)

(09264)612804103

Columbia DBL (Pty) Ltd* (021)9051665 Stanger Brick & Tile (Pty) Ltd* (032)4570237

Deranco Blocks (Pty) Ltd* (041)4633338 Watson Concrete*(011)7400910(011)8733949

False Bay Bricks (Cape)* (021)9041620Western Granite Bricks (Pty)Ltd*

(021)9041620

Inca Masonry Products (Pty) Ltd* (043)7451215 White River Cement Bricks (013)7501271

Infraset* (012)6520000 Lategans Cement Works* (021)8731154

*Companies which hold the SABS mark

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Acoustic Wall[1]