ACHRNEWS

Designing Systems To Decrease Noise

October 30, 2003
As the world goes at a faster pace and technology becomes a blur, one of the residual effects of daily life's breakneck speed is noise. Noise levels, measured in decibels, have risen as more vehicles jam America's highways, construction equipment builds high-rises on postage-stamp-sized lots, and people chat on cell phones, oblivious to their contributions to noise pollution.

While the increase in decibel levels is often more of an annoyance than a health concern, there is one place where more noise can have a detrimental effect on the learning process - in schools. More noise means louder talking by teachers and students, and sometimes results in miscommunication in the classroom. In a report by the League for The Hard of Hearing, the group said, "Studies have shown that poor classroom acoustics negatively affect learning."

The League points to a report by David Lubman titled America's Need for Standards and Guidelines to Ensure Satisfactory Classroom Acoustics, which states, "Acoustical conditions in many classrooms are unsuitable for such tasks as learning to read, to listen, or to understand unfamiliar material. Poor classroom acoustics are frustrating for both students and teachers, as indicated in teacher surveys. According to the Acoustical Society of America, in many classrooms in the United States up to 25 percent of the information can be missed because of excessive noise and reverberation."

Lubman commented, "Teachers are less likely to talk with students or will talk with them for shorter periods when noise levels are high."

A new standard on classroom acoustical design, developed by the American National Standards Institute (ANSI) Committee on Noise (S-12) under the authority of the Acoustical Society of America (ASA), is addressing the noise pollution problem.

Dr. Robert Seel, director of technical services for Emerson Climate Technologies, Sidney, Ohio, gave some background on ANSI Standard S12.60, "Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools."

"These are acoustical design guidelines for new construction and renovated school buildings," he said. "The overall concept is to study the background noise levels in intermittent times to obtain a signal-to-noise ratio for good speech intelligibility in learning spaces. The standard suggests testing the sound levels at various times of the day in unoccupied spaces.

"The standard recommends a steady background noise of 35 dBA, which is equivalent to a soft whisper at two meters."

The Lubman report cited many American classrooms with an unoccupied level of 50 dBA and gymnasiums exceeding 60 dBA.

Seel said the standard proposes a "perfect learning situation" for students factoring in contributions from outside noise, such as road noise. Inside the classroom, the standard takes into account the noises from HVAC systems.

"We are looking at contributions from fan noise, ventilation, etc.," he said. "Like all standards, these are not laws, only recommendations. But building codes will be reflective of this new standard.

"Some people have said that 35 dBA is a very stringent standard. In fact, I don't know of any that have lower recommended levels."

Dr. Ali Herfat, global reliability manager for Emerson Climate Technologies, said, "This is a new standard for classrooms which was developed because students are having a hard time hearing the instructors.

"ANSI studied this problem and with input from the Air-Conditioning and Refrigeration Institute [ARI], S12.60 was passed in 2003, and it is now a national standard.

"Several different classrooms were studied and this number [35 dBA] was found to be the most acceptable for background noise levels."

What One Company Is Doing About It

Design Services Network, a company of Emerson Climate Technologies, also located in Sidney, Ohio, provides extensive HVACR testing and thermal system design capabilities to OEMs and end users. The company is heavily involved in testing the performance, quality, and safety of equipment; conducting sound and vibration tests; and acting as consultants for designing equipment and buildings that meet certain sound standards.

Chris Mays, program manager for Design Services Network, gave The News some information on S12.60, which will help schools develop a "sound map" of the school to find out where improvements are necessary and detail other factors schools should consider when trying to make their classrooms quieter.

"We are an engineering consulting group that helps OEMs design air conditioning and refrigeration equipment," said Mays. "Sound testing is also one of the capabilities that we have.

"We can help the educational market by assisting OEMs and end users in the design of sound-optimized equipment, recommending system improvement so that they are not out of compliance with S12.60."

Mays said that his group's ultimate goal is to "incorporate and leverage all Emerson components into the quietest design for OEMs. We can leverage the fan division, the motor division, and the compressor division - the sound makers - and offer them into an integrated design."

He said that during sound mapping, his group sets up test equipment in a classroom to measure sound levels, background noises, etc. This becomes useful if a school is looking to retrofit.

"We can provide a good baseline of the current status of what a building is reading [dBA]," Mays said. "We can then make recommendations on how to reduce noise levels, whether it is the HVAC system, lighting, or whatever else."

Mays said that HVAC equipment can be modified in various ways. "We can recommend a different fan setup, quieter motor, sound blankets for compressors, etc. There are a lot of tricks to making a system quieter - it is a matter of evaluating existing equipment and seeing how it can be improved."

Getting Contractors Involved

Mays said that HVACR contractors can view system design with reduced noise levels as a value-added sell.

One concern is that contractors may be installing equipment that is not compliant with Standard S12.60 recommendations. "They may not be aware of the equipment that is available," he said.

"The infrastructure and depth of Design Services and Emerson Climate Technologies supports the contractor, no matter how large or small he is," Seel stated. "In a sense, Emerson is a one-stop shop.

"It can be a sound issue involving fans, compressors, etc., and we can produce reports for contractors to help them understand which direction to go in.

"There is an element of risk for a contractor to pick up the phone and call a consultant. With Emerson, we have a good track record and reputation for quality.

"We can work together and provide solutions for the customer."

Publication date: 11/03/2003