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HomeMy WebLinkAbout13.F.1. Library Acoustical Report Ij,F, /. CITY OF SHAKOPEE Memorandum TO: Mayor and City Council FROM: Mark McNeill, City Administrator SUBJECT: Library Acoustical Report . DATE: Sept. 16th, 2008 Comment: Introduction: Council has asked to review the results of an acoustic report that was done at the library and building, and give direction as to the next step. Background: Earlier this year, the City Council authorized that an acoustical sound study be performed at the Library building. This was in response to complaints from library staff that noise has been an issue ever since the building was open in 2003. Kehl Associates of Minneapolis performed a preliminary study, at the recommendation of BKV group, the architects for the structure. The study report is attached. In summary, the problem results from a variety of causes, starting with the open two story atrium at the entry. The atrium has mostly hard surfaces as its floor and walls, which reflect rather than absorbing noise from doors closing, conversations, foot traffic, and vending machines. The report also notes that the library may be "too quiet". As such, what would be considered normal background noise in the atrium is perceived as being a problem. The Report suggests five possible solutions to eliminating the noise issues: 1. Install additional acoustic absorbing material. The recommendation is that fiberglass panels be installed in the wall and door areas of the atrium, and surrounding the vending machines. In addition, banners or acoustical baffles could be hung in the upper atrium to help dampen the atrium noise. Approximate cost: $18-24,000 2. Carpet the atrium. Note that there would be some added maintenance efforts as a result, especially during the winter. Approximate cost: $4-8,000 3. Contain atrium noise. This would be to install acoustic panels in the second level of the atrium, which would deflect, as well as absorb sound. Approximate cost: $8-12,000 4. Install a floating ceiling grid of clear plexiglas. This would reflect noise downward to where it could be contained in the glass end portion ofthe atrium, and would also allow people to hear themselves better, which will cause them to reduce the volume of their conversation. Approximate cost: $6-10,000 5. Create masking noise. One of the problems with the current "quiet" ambient noise level is that normal noise seems loud. The recommendation is that a water feature such as a decorative water fall be installed in the upper atrium above the side wall reflectors and center ceiling grid. The recommendation would also add miniature loud speakers, which would amplify this steady and soothing background noise to help mask noise from the atrium. Approximate cost of electronic system: $8-12,000 Approximate cost of water feature: To be determined However, before proceeding with any of these possible solutions, the acoustical consultant recommends that field measurements be performed in the building to determine the sound pressure level of the existing noise issue. In this, microphones would be set up throughout the library at a time when the building is closed, and testing would be done to establish a base level of noise. Then, as steps are added to address the noise, measurements could subsequently be done to find out how effective a particular solution might have been. This would eliminate the subjectiveness of relying upon individual perceptions of whether a solution assisted the problem, or not. The initial cost ofthe baseline of the field measurement would be $3-4,000. Subsequent measurements, to be taken following installation of the various steps, would be $1-2,000. Please note that there is no requirement to do the sound study. We could proceed with installing the acoustic wall panels as step one, and then do step two, etc, until the problem is deemed as being resolved. However, that would be dependent upon satisfying the varying perceptions of individuals, rather than doing something that is quantifiable. If approved by Council to proceed with the field measurements, BKV would then use the results to put together specifications and would coordinate the solicitation of quotations for the installation of the acoustic panels, as described in Step 1 of the report. BKV is donating their services to the City at no cost. Once the quotes are received for those panels, the decision would be brought back to the City Council as to approval to purchase and install. Budget Impact: The 2008 budget provided for $40,000 for noise treatment at the library. Study cost incurred thus far has been $5000, meaning there is $35,000 available for treating the noise problem; Recommendation: So as to establish a baseline level of the noise at the library, I recommend that Kehl Associates be authorized to perform acoustic field study, and to proceed with solicitation of quotes for the installation of acoustic panels. Relationship to Visioning: This supports Goal B (High Quality of Life). Action Required: Ifthe Council concurs, it should, by motion, authorize Kehl Associates to perform field measurements for library noise, and to have quotations taken of the installation of acoustic panels. 1.L& ~. MAli Mark McNeill City Administrator MM:cn . 1 ,.."J , 00 PREUMiINARY ACOUSTICAL ANALYSIS REPORT (Qr Sbakopee Public library S~~~opee, Mmfl~ta ~red by iKehl Asrotlatfi. 1m:. M.nfl~.a~ Mmrerota ~Da~:_a2D " Shakopee Public Library Page 1 of 5 , Preliminary Acoustical Analysis Report July 2, 2008 Kehl Associates, Inc. INTRODUCTION The purpose of this report is to: 1. Document the acoustical issues reported at Shakopee Public Library. 2. Present the results of the on-site inspection and acoustical analysis that were performed in conjunction with this project. 3. Offer discussions of observations, causes, and remedies to the issues. 4. Present various solutions that may be implemented as the Owner desires. Preliminary cost estimates are included herein. It should be noted, however, that these are ballpark estimates offered simply for relative comparisons between solutions. These costs should not be used for budget allocations. Selected solutions should be further investigated prior to allocation of construction budgets for this project. BACKGROUND/REPORTED ISSUES The new Shakopee Public Library has a front entrance that opens to a 2-story Atrium, from which the various rooms and spaces in the Library are accessed. The Atrium separates the Library into two sections, with bridge access through the Atrium between the sections on the second floor. The Atrium currently has acoustically reflective floor and wall surfaces, with minimal acoustical treatment. The second story of the Atrium is open to the second floor of the Library, which is divided in two by the Atrium. The hard surfaces of the Atrium create an acoustically reverberant space where medium level noises, such as door closings, conversational speaking, traffic footfalls, and vending machine noise, are heard at levels that seem intrusive. The intrusiveness of this noise is amplified by the fact the ambient noise level in the Library proper is low, as is common for libraries. These intrusive noises are heard throughout the second floor of the Library, and are a disturbance to people using these spaces. OBSERVATIONS/DISCUSSION Our on-site observations confirmed the reported issue: sounds generated in the Atrium are intruding on the second floor of the Library due to air-borne sound transmission between the spaces. There are multiple contributing factors to this issue as discussed below. NO SOUND BLOCKING BARRIERS Due to the open nature of the interior design of the building, there are no sound blocking barriers between the spaces to mitigate sounds between the Atrium and the upper libraries. Adding such barriers, of course, is the most straightforward approach to minimizing the noise issue. This effort would need to include doorways at the ends of the bridges to be truly effective. In addition, additional acoustical treatment would most likely be necessary in the Atrium, though not as much as would be necessary in other solutions described herein. ~ Shakopee Public library Page 2 of 5 Preliminary Acoustical Analysis Report July 2, 2008 Kenl Associates, Inc. MORE ACOUSTICALLY ABSORPTIVE MATERIALS Secondly, there is insufficient acoustically absorptive finish materials in the Atrium to minimize the sound levels of the noise being generated therein. In fact, the hardness (acoustical reflectivity) of the finish materials tends to amplify the sounds originating in the Atrium. This has a tendency to cause people in the Atrium to speak louder than usual to overcome the noise of the reverberant sounds of their own voices, thereby escalating the noise issue. To minimize this situation, the reverberant field in the Atrium needs to be absorbed by adding acoustical treatment to the space. Absorption should be added in such a way so as to preserve or create acoustically reflective surfaces that are in close proximity to the people speaking in the space. This will allow them to hear themselves more clearly and cause them to speak more quietly. This could be accomplished by adding overhead panels that ae acoustically reflective, but may be better accompliShed with overhead absorptive barrier panels. In addition, wall and floor acoustical treatments would be needed. TOO QUIET Finally, the Library may be too quiet for its own good. It is almost universally accepted that libraries should be designed to be quiet. Our onsite observations confirmed that this Library reflects that goal. It is so quiet, when the Atrium is unoccupied, that you could almost hear a pin drop. This same characteristic makes it easier to hear Atrium conversations and the closing of Atrium doors. This quietness creates an atmosphere in which any sound becomes intrusive. Part of our solution, then, may be to generate steady, low-level, unobtrusive sounds to help mask the obtrusive sounds coming from the Atrium. It has long been our opinion that libraries in general could greatly benefit from some sort of electronic noise masking to do just that, mask obtrusive sounds. Such systems have been used for decades to provide speech privacy in open office areas and in the waiting rooms of confidential conference and counseling rooms. These systems generate a pleasing, soothing type of sound at a level that masks speech conversation, but is not loud enough to be intrusive itself. They mask the sound of other noise so that you cannot eavesdrop on the conversations of others nor can you hear that pin drop. In most places where properly designed electronic noise masking systems are in use, those hearing them are not aware of their presence. They are generally accepted as being part of the ambient building noise. In open office areas and waiting rooms the systems are usually electronic. However, in Atriums it is not uncommon to see water features that generate comparable noise masking sound, such as the fountain in the Crystal Court of the IDS Center. For the Shakopee Library Atrium, a combination of electronic and natural sounds might be the best solution: a small water feature (waterfall or fountain) that utilizes electronic amplification to generate a louder sound, thereby allowing the water feature to be smaller and less costly. The electronic portion of this type of system would be relatively inexpensive due to the nature of the sound field being generated. That is, because of the water feature, the sound could simply emanate from the Atrium instead of emanating from the entire Library ceiling, as in a normal open-office masking system. A single row of speakers in the upper libraries on either side of the Atrium may be sufficient to create the needed effect. This solution may be pivotal to the success of this project. \ Sl1akopee Public library Page 3 of 5 Preliminary AcoustlrEI Analysis Report July 2/ 2008 Kehl Assodates, Ille. SOLUTIONS The following recommendations are presented as possible solutions to the current issues in this space. We present here a number of solutions that may be accomplished incrementally, in order to conserve funds while obtaining the level of noise reduction desired. ADDrnONALABSOR~ON 1. The first step in minimizing Atrium noise is to provide additional acoustical absorption in the Atrium and at the vending machine area. The walls should be treated with fiberglass panels. This would include: . all of the wall and door areas, except the windows, glass walls and glass doors . the areas in front of, and in back of, the vending machines . the sides and top of the windowed Atrium archways in the upper Library Lower wall areas, below 7 or 8 feet, should utilize "high-abuse" acoustical panels that utilize perforated co-polymer facing for durability. Upper wall areas may use less expensive fabric wrapped acoustical panels. Additionally, banners or acoustical baffles of various sizes could be hung in the upper Atrium to help dampen Atrium noise. Specifically, vertically hung acoustical baffles or banners hung from the beams between the second floor Atrium windows to the Library would be particularly effective. These banners should be 2-4 inches thick, approximately 3-4 feet wide and 6 or more feet long. To minimize noise reflections from the Atrium into the second floor Library windows, Approximate Cost: $ 18-24,000 Materials: Wall Technoloov - www.wa//techn%gy.com High Abuse Wall Panels - 2" thick: Rebound, Metro Rebound, or Metro Wood Standard Fabric Wrapped Wall Panels - 2" thick: AiOO Series Unoer Technolooies - www.enoisecontrol.com Acoustical Banners - 2" or 4" thick - Model AB-150 Acoustical Banner 2. The second step in minimizing Atrium noise is to carpet the Atrium. The carpet should be a heavy material with padding as thick as is reasonable for the space. Approximate Cost: $ 4-8,000 Shakopee Public Library Page 4 of 5 Preliminary Acoustical Analysis Report July 2, 2008 Kehl Associates, Inc. CONTAINING ATRIUM NOISE 3. The third step in minimizing Atrium noise is to install acoustical panels along the sidewalls of the Atrium at a height slightly above the wall light fixtures. These panels may all be installed at the same level or staggered within 1 foot. These panels should be 3-4 feet wide and 4-12 feet long. They may be set out from the wall approximately 3-6 inches. They should be canted up toward the center of the Atrium at an angle of 25-30 degrees. There are two types of panels that could be used for this purpose with varying results: A. An acoustically absorptive sound barrier panel would yield the best results. These panels block sound as well as absorb it. Two panels should be installed back-to-back to provide absorption for both the upper and lower Atrium. The panels would be covered with fabric or perforated co-polymer facing to match the wall panels. These panels will help stop sound from traveling to the upper Atrium while also helping to absorb sound in the upper and lower Atrium. B. A clear Plexiglas panel could also be used, as it may be more aesthetically pleasing. These panels should be a minimum of V2-inch in thickness to provide enough mass to stop or reflect sound. These panels will help stop sound from traveling to the upper Atrium while slightly amplifying sounds in the lower Atrium. Approximate Cost: $ 8-12,000 Materials: Wall Technoloqy - www.wal/techn%gy.com Absorptive Barrier Panels - 2" thick: Loaded Vinyl Acoustical Panels 4. The fourth step in minimizing Atrium noise is to install a floating ceiling grid of clear Plexiglas. This ceiling should be installed down the length of the Atrium at a height that is 1-3 feet above the sidewall acoustical panels. This ceiling grid would be approximately 8 feet wide and comprised of V2-inch or thicker Plexiglas panels. Its purpose is to contain Atrium sounds to the Atrium by reflecting them back into the Atrium or into the sidewall acoustical panels where they will be absorbed or reflected. Approximate Cost: $ 6-10,000 Materials: Standard construction materials in custom configuration Shakopee Public library Page 5 of 5 Preliminary Acoustical Analysis Report Ju!y 2, 2008 Kenl Associates, Inc. CREATING MASKING NOISE 5. An additional step in minimizing Atrium noise is to install an electronic noise masking system in conjunction with a water feature. The water feature should be located in the upper Atrium above the sidewall reflectors and center ceiling grid, so as not to add more noise to the lower Atrium. Miniature loudspeakers would be located directly in or around the water feature. Additional loudspeakers would be located above the ceiling in the upper libraries along the Atrium windows. The loudspeakers would prOVide a pleasant waterfall, stream, or fountain type of soothing, steady background sound to help mask the noise from the Atrium. The water feature would create the illusion that the sound was natural, emanating from the water feature itself. In actuality, much or most of the sound would actually be generated by the electronic system. Approximate Cost of electronic system: $ 8-12,000 Approximate Cost of water feature: to be determined RECOMMENDATIONS Based on our assessment of the Owner's expectations and the issues identified, we feel that the solutions defined herein will eliminate or substantially minimize the noise issue and will provide results that will meet the Owner's needs. Although the best results will be obtained by implementing all of the solutions defined herein, we recommend that the solutions be implemented incrementally, so as to implement only as many solutions as are needed to meet the Owner's expectations. Before any solutions are implemented, field measurements must be taken to determine the Sound Pressure Level of the existing noise issue. With this information, it will be pOSSible to quantify the results of each implementation phased. Additional measurements would be taken at the completion of each phase of implementation. We recommend the following actions: A. Perform Acoustical Field Measurements to determine the Sound Pressure Level of the existing noise issue. B. Implement Solutions 1 and 2: Acoustical Wall Treatment and Carpeting. These solutions may be enough to lower the noise to satisfactory levels. C. Perform Acoustical Field Measurements to evaluate the effectiveness of the implemented solutions and determine the best next step. The best next step may be to implement Solution 3 or Solution 4, independently or together. Alternatively, it may be preferable to implement Solution 5, the Water Feature/Noise Masking Solution, at this time. The results of the Field Measurements will determine the best path. . Shakopee Public Library - Kehl Associates, Inc. Index Page 1 APPENDIX This section include cut sheets on various acoustical treatment materials described in this report. Wall . 4~:~"- ~. Technology . An~fI$ComilJgCcmpqflY A 100 Series Acoustical Panels SUBMITTAL SHEET " APPLICATION . Wall ff}Chflblogy's A 100' Series panel is an economical, all purpose acoustical wall and ceiling panel designed for use where sound absorption and value are the main criteria. This series panel is suitable for auditoriums, theatres, offices and libraries: anywherel16isecontrol is-needed and critical lighting and high abuse resistance are not factors. CONSTRUCTION The core construction is a dimensionally stable 6-7 PCF glass fiberboard with chemically hardened edge protection. Finishes are completely adhered to the face of the panel and returned to the back for a full finished edge. All comers are fully tailored. SIZE AVAILABILITY Available thicknesses are 1/2", 3/4",1",1-1/2",2",3", and 4". Widths are up to 48", and lengths to 12'. 1" and 2" are available in 60" x 120". Custom size is our standard! EDGE DETAIL All edges are resin hardened, unless otherwise specified. Available choices include: square, radius, bevel, and radius corners. -'''. FINISH A wide varyety of fabrics are available from all major brands, including Guilford, Maharam, Knoll, Carnegie, and Designtex. A comprehensive selection of vinyl coverings is available from Webcore, Designtex and Maharam. A USDA-approved Tedlar encapsulation can be provided for areas where sanitation and clean-ability are mandatory. MOUNTING Standard mountings include spot and perimeter adhesive, Z-clip, concealed splines, impaling clips, hook & loop, and magnetic fasteners. Wall Bar to Wall Bar is recommended for ceilings. SUPERIOR ACOUSTICAL PERFORMANCE A 100 Acoustical Wall and Ceiling Panels provide excellent acoustical performance for auditoriums, theaters, offices, libraries, and classrooms and virtually anywhere sound absorption is required. A 100 panels carry the UL classification label for your , Shakopee Public Library - Kehl Associates, Inc. Index Page 2 assurance of acoustical performance. ~.'P, ~ Noise ReducUon Coefficient ACOUSTICAL UL USTING A 100 fabric wrapped panels have been tested at Underwriters Laboratories for their acoustical performance. The following NRC listings are available for a Type A mounting: Thickness NRC %" .70 1" ,80 1 }'2" .95 2" 1.053" 1.15 The noise reduction coefficients were derived from tests conducted by UL in accordance with ASTM C 423 on a Type A mounting. FIRE PERFORMANCE Each component has been tested according to ASTM E 84* and has a Class IJA rating. .. ~ - - ........-. - - :::: e~ ....CERTIAED SCIENTIFIC CERTIFICATION SYSTEMS RECYCLED CONTENT A 100 panels utilize an Owens Corning fiberglass board core that is eligible to bear the Green Cross label for recycled content. The board is certified on average to contain at least 35% recycled glass, with 9% post-consumer and 26% pre- consumer content. And for your LEED project, our acoustical panels can help you qualify for recycled content points under the Materials and Resources section. Other LEED categories may also apply depending upon the project requirements. 3- Year 3-Year Walls /1-Year Ceilings A 1 00 Series Acoustical panels have a limited 3-year warranty when used on walls, and 1-year on ceilings; starting from date of purchase. The panels are warranted to be free from defects in material and workmanship. See product warranty for limitations. . The ASTM E 84 standard should be used to measure and describe the properties of materials, products or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment, which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use. Values are reported to the nearest 5 rating. ,. -~ 1III0WI1l!lS fOR UYlIlli- Pub. No. 10000533 Printed in U.S.A. September 2006. <>2006 Owens Corning. . . Shakopee Public Library - Kehl Associates, Inc. Index Page 3 _Wall 'j .,I~~~~ Metro Wood Panels SUBMITTAL SHEET APPLICATION Metro Wood wall and ceiling panels are designed for use in high abuse areas requiring sound absorption and clean-ability. A "pan" of perforated co-polymer over fiberglass allows sound absorption while withstanding many forms of punishment. Use in gymnasiums, hotels, multipurpose rooms - anywhere requiring a durable, acoustically absorbent panel with a faux wood finish. CONSTRUCTION This panel features an innovative combination of dimensionally stable 6-7 PCF glass fiberboard, with a 1/16" resilient perforated co-polymer face sheet with heat-formed edges. A white or black scrim layer is optional under the copolymer sheet. SIZE AVAILABILITY Thicknesses include: 1-1/16", 1-9/16" and 2-1/16". Widths are up to 48" for 1" and 46" for 2". Lengths are up to 116" for 1", and 114" for 2". Standard tolerance is:!: 1/8"; a reveal of 1/8" is required between panels. Custom size is our standard! EDGE DETAIL All edges, square only, are resin hardened underneath the heat-formed co-polymer. FINISHES The co-polymer is available in 6 standard wood-grains. From light to dark this includes: Riga Birch, Honey Maple, Pearwood, Wild Apple, Spiced Fruitwood and Black Cherry. MOUNTING Standard wall mountings include; spot adhesive with optional impaling clips, Z-clip, hook & loop, and magnetic fasteners. Wall bar to wall bar is the recommended ceiling mount. . . Shakopee Public library - Kehl Associates, Inc Index Page 4 ACOUSTICAL PERFORMANCE Metro Wood Acoustical Wall and Ceiling Panels provide excellent acoustical absorption. Panels have been tested in accordance with ASTM C-423 with Type A mounting by a NVLAP approved Laboratory: 1-1/16" Thickness NRC = 0.75 2-1/16" Thickness NRC = 0.95 FIRE PERFORMANCE Each component has been tested according to ASTM E 84* and has a Class I/A rating. I- - ----... -::::... ;~ · CERnFIED SCIENTIFIC CERTIFICATION SYSTEMS RECYCLED CONTENT Metro Wood panels utilize an Owens Corning fiberglass board core that is eligible to bear the Green Cross label for recycled content. The board is certified on average to contain at least 35% recycled glass, with 9% post-consumer and 26% pre-consumer content. And for your LEED project, our acoustical panels can help you qualify for recycled content points under Materials and Resources. Other categories may also apply depending upon project requirements. 3- Year 3-Year Walls /1-Year Ceilings Metro Wood Acoustical panels have a limited 3-year warranty when used on walls, and 1-year on ceilings; starting from date of purchase. The panels are warranted to be free from defects in material and workmanship. See product warranty for limitations. . The ASTM E 84 standard should be used to measure and describe the properties of materials, products or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment, which takes into, account all of the factors, which are pertinent to an assessment of the fire hazard of a particular end use. Values are reported to the nearest 5 rating . .. Shakopee Public Library - Kehl Associates, Inc. Index Page 5 1'6/~.WalI ... .,/ ..Technolggy / AA_~~ Metro Rebound Panels SUBMITTAL SHEET APPLICATION Metro Rebound wall and ceiling panels are designed for use in high abuse areas requiring sound absorption and clean-ability. A "pan" of perforated co-polymer over fiberglass allows sound absorption while withstanding many forms of punishment. Use in gymnasiums, hotels, multipurpose rooms - anywhere requiring a durable, acoustically absorbent panel. CONSTRUCTION This panel features an innovative combination of dimensionally stable 6-7 PCF glass fiberboard, with a 1/16" resilient perforated co-polymer face sheet with heat-formed edges. A white scrim layer is optional under the co-polymer sheet. SIZE AVAILABILITY Thicknesses include: 1-1/16", 1-9/16" and 2-1/16". Widths are up to 48", and lengths to 116" for 1", and 114" for 2". Custom widths up to 51" are available with 1-1/16" thickness. Standard tolerance is:!: 1/8"; a reveal of 1/8" is required between panels. EDGE DETAIL .. ........ - - ~ ... - == j!!.~ .. CERTIFIED All edges, square only, are resin hardened underneath the heat-formed co-polymer. SCIENTIFIC CERTIFICATION SYSTEMS FINISHES . ' . . F Public Library - Kehl Associates, Inc. Index Page 6 The co-polymer is available in 8 standard colors with many custom colors also available. MOUNTING Standard wall mountings include; spot adhesive with optional impaling clips, Z-clip, hook & loop, and magnetic fasteners. Wall bar to wall bar is the recommended ceiling mount. ACOUSTICAL PERFORMANCE Metro Rebound Acoustical Wall and Ceiling Panels provide excellent acoustical absorption. Panels have been tested in accordance with ASTM C-423 with Type A mounting by a NVLAP approved Laboratory: 1-1/16" Thickness NRC = 0.75 2-1/16" Thickness NRC = 0.95 FIRE PERFORMANCE Each component has been tested according to ASTM E 84* and has a Class If A rating. RECYCLED CONTENT Metro Rebound panels utilize an Owens Corning fiberglass board core that is eligible to bear the Green Cross label for recycled content. The board is certified on average to contain at least 35% recycled glass, with 9% post-consumer and 26% pre-consumer content. And for your LEED project, our acoustical panels can help you qualify for recycled content points under the Materials and Resources section. Other LEED categories may also apply depending upon the project requirements. Pub. No.1 0000543. Printed in U.S.A. September 2006. <>2006 Owens Corning. '" ...,.. . , , \ < " Shakopee Public Library - Kehl Associates, Ioc. Index Page 7 ~U......-. . -. ~...... -~. .. . Llt:K ~.. TECHIIULUG.IE5 , ... . I N.C. T Acoustic Banners Model AB-150 Acoustic Ceiling Banners provide excellent sound absorption. They are especially effective and cost efficient for facilities that require large amounts of sound absorption. These banners are easily cleanable, because of their PVC covering. The banners are typically designed to hang parallel to the ceiling via grommets and/or metal mounting stays. Features: · Class 1 fire-rated · NRC ratings 1.00 -1.15 · Custom sizing up to 4'x40' · 2" or 4" thickness Applications: · Gymnasiums · Multi-Purpose rooms · Industrial! Manufacturing plants . · Auditoriums! arenas · Restaurants! night clubs · AN production rooms · Animal Shelters + hospitals .. , -I- . 1 / , r' -. Shakopee Public Library - Kehl Associates, Inc. Index Page 8 Acoustical Performance: Sound Absorption Coefficients OCTAVE BAND FREQUENCIES (Hz) Product 125 250 500 1000 2000 4000 NRC 2"thick 1.09 ~97 .92 1.05 1.00 1.11 1.00 4"thick 1.31 1.11 1.14 1.17 1.15 1.19 1.15