Engineered Systems - June 2008 - (Page 11)

Letters Noise attenuation: a light touch Ed.note: The next two letters pertain to John S. Clark’s article “Congregations In Comfort,” which appeared in the January 2008 issue of Engineered Systems (page 72). I have been a consultant in acoustics and noise control for over 35 years, and I find that an important consideration in worship spaces (as well as or school rooms) is the hearing conditions, another comfort issue, if you will. True, the matter of economics figures heavily into both environments. But good hearing is mandatory for churches as well as our schools (especially among the young). In this modern era of forced air HVAC, fan and circulation noise is always with us, so noise control is always an issue if these occupied public spaces are to perform their mission well. Acoustical consultants work daily on this optimization. We devise ways of engineering cost vs. benefit and we strive to satisfy both. For instance, I have designed and recommended that an inexpensive lined “plenum,” fashioned solely by the mechanical contractor, be tucked somewhere into the air supply and the air return ducting systems in lieu of “expensive attenuators.” I also recommend the use of flexible ducting instead of some lengths of hard-walled sheet metal ducting (flexible ducts allow fan noise to escape harmlessly before the air is delivered to the occupied space). The grilles over air return duct opening are a frequent and a strong source of noise in worship spaces. Simply omitting them, or widening the spaces between their vanes, is the quietest and cheapest solution. So there are ways to beat the odds in this noise control game. shape, and whether a sound reinforcement system is planned. Just as other HVAC design parameters are engineered, the HVAC system can be engineered to meet the needed target value of background noise so that people will hear well. What else is a worship space for it not for good hearing? • Three things make noise in air-handling systems: fans, air turbulence in ducts and fittings, and air turbulence at diffusers and grilles. Lowering air speeds is the method of choice for controlling noise of the second and third; fan noise can only be controlled via used of duct silencers or duct liner if there is insufficient attenuation offered naturally by the supply and return duct system. My point for readers of Engineered Systems is that air-handling systems for worship spaces can be engineered to meet both thermal comfort and acoustical needs. Readers may be interested to know that acoustical consultants across the country providing advice on such matters are listed on http://ncac.com/, the website of the National Council of Acoustical Consultants. Anyone can claim to go the distance. Edward M. Clark, P.E. Principal Ostergaard Acoustical Associates W. Orange, NJ AERCO. Built better to last longer. Benchmark Boilers. Proven technologies and superior materials make the difference. Twenty years of high-efficiency experience go into every unit we sell. Designed and warranted for condensing operation and thermal shock, AERCO utilizes stainless steel fireside materials for superior corrosion resistance and unmatchable performance … year after year. To learn more visit www.aerco.com/bm4 Clark responds: Being able to hear the “Spoken Word,” in a worship space, is the first priority in dealing with the acoustic solutions applied to both the building space and the HVAC system. Most church construction projects have an acoustical consultant as a member of the design team. This consultant works with the architect, the HVAC engineer, the sound system engineer and the church’s building committee to arrive at visual solution, a comfort solution and an acoustical solution that fits within the construction budget. In my over 40 years of experience as both a designing mechanical engineer and a member of church building committees, this team process works very well. The mechanical engineer team member must be aware of all the noise sources from fans, duct turbulence, and diffuser/grille terminal velocity. A range of economic solutions is available to deal with all the objectionable space air noise. The range of Angelo Campanella, Ph.D., P.E. I found the “Silence May Not Be Golden” to include several misguided generalizations on acoustical design of air-handling systems for worship spaces. Based upon my 30 years of experience with the design of air space for good hearing, here are some facts readers may not be aware of: • The background sound level appropriate for a new worship space can be identified knowing such parameters such as the farthest talker-listener distance, the room Copyright 2008 AERCO International, Inc. Heat You Can Bank On Input 72 at www.esmagazine.com/instantproductinfo w w w. esmag a zine . c o m ESM02084AERO.indd 1 11 1/16/08 1:33:29 PM http://ncac.com/ http://www.aerco.com/bm4 http://www.aerco.com/bm4 http://www.esmagazine.com/instantproductinfo http://www.esmagazine.com

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Engineered Systems - June 2008 Contents Editor’s Note Letters To The Editor Back2Basics HVAC Challenge Case In Point Commissioning Efficiency Incentives HydroTech Building Automation Energy Wiz HVACR Designer Tips Notre Dame Tackles the Heat State Of The Arts Time For A Transplant? Project Delivery: What Can IPD Do For You? Issues & Events Computers & Software Products Application Checklist Glossary Classifieds Advertiser Index Tomorrow’s Engineer

Engineered Systems - June 2008

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