rating, but without a high OITC rating, low-frequency sounds can be intrusive,” Merck said. “Windows with a high STC rating typically have the same OITC rating as windows with a lesser STC rating, which can be a bit misleading. Ratings that include the OITC are more useful to assess how well a window will isolate environmental noise.” Albert Maniscalco, a partner with Cerami & Associates in New York, said it’s important to know all aspects of the project to determine which rating might be more essential. “If I’m designing a school, a music practice room might need an acoustical door so that the sound doesn’t bleed out,” he said. “In New York City, there are regulations about OITC to mitigate noise from the exterior. It has become more of an is- sue to control exterior noise. OITC ratings were adopted because STC ratings didn’t paint the whole picture.” Acoustical design can play a part in the design of any commercial struc- ture. Cerami, for instance, has its acoustical imprint on such diverse projects as the Metropolitan Museum of Art, Grand Central Station and a library at Barnard College in New York. In those applications, the STC rating might be more essential than the OITC rating. The point is that in any project, acoustical engineers need to find the best materials to balance the delicate equilibrium for noise control. Besides the Great Lakes Center for the Arts, BILCO acoustical smoke vents have been installed in projects big and small. The Hale Centre Theatre in Utah includes 20 acoustical smoke vents in a 133,000 square foot building. Middlesex School in Massachusetts used six acoustical smoke vents in the renovation of a 55,000 square foot auditorium. When it comes to acoustics, any building can be improved by choosing the correct building products. “It’s the balance of creating design, and how does acoustics layer into that to be able to give those areas focus,” Victoria Cerami, CEO of Cerami &Associates said in a video where she discussed acoustics and the workplace. “Each space should have its signature, its acoustical signature. And it should correlate with the design intent.” Cultural Centerpiece The Great Lakes Center for the Arts provides an important piece to the arts community in Northern Michigan. The acoustical smoke vents help keep the occupants safe, while also allowing them to enjoy the diverse experiences from its creative lineup of performers. Novotny and his team faced a lot of architectural choices in the design of the Center. First and foremost, however, was creating a space that patrons of the arts would enjoy from the moment they set foot in the facility until the last note of every concert and final sentence of every reading. Aesthetically, visually, and acoustically, the final product hit all the right chords. “This building adds a space for world-class performers that did not exist in northern Michigan,” Novotny said. “It adds to the valuation of the performing arts community that was intended by the clients.”
impacting a building facade with significant low-frequency (bass) sound,” says Harold Merck, principal and acoustician for Merck & Hill Consultants of Atlanta. “While STC ratings may be fine for typical in- terior noise sources such as voices, STC doesn’t adequately address the extended low-frequency noise contribution of aircraft, traffic or even large roof-top equipment. This also applies to large roof-top equip- ment noise sources as well. The OITC better addresses low-frequency noise impacts and is the more applicable sound rating for roof mounted automatic smoke vents.” STC measures the extent to which sound is prevented from being trans- ferred from one area to another. The higher the STC value, the less that sound can be transferred through a building product. STC is typically used to measure sound transmission loss over a frequency range from 125 to 4000 hertz and is most applicable for interior areas that experi- ence mid to high frequency noises, such as conversation, television, telephones, and office equipment. A product with a high STC value, ranging from 50-60, indicates that loud speech is barely heard, if at all. A low STC rating, 20-25, indicates that loud speech is audible. OITC Ratings: A Deeper Dive Earlier this year, BILCO introduced a new automatic smoke vent that provides the highest level of protection against exterior noise intrusion. The new model carries an OITC-46 sound rating and an STC sound rating of 50. Most acoustical smoke vents have an OITC rating of 39 or less The vent also has an ISO 140-18 Rainfall Sound Rating, which mea- sures the impact sound insulation, roof, skylights and roof/ceiling sys- tems incur when exposed to artificial rainfall. BILCO’s new ACDSV’s rating of 37.5 dB features a nearly nine percent improvement over its previous four-cover smoke vent models. “While any noise can be disruptive to a concert-goer, lower-frequency sounds such as outdoor traffic, construction and airplane noises travel further and fall within the range where human hearing is most sensi- tive,” BILCO General Manager Michael Toohey said. It’s critical for architects to understand the project so that they can adjust for the noise control. “Windows might have an excellent STC The BILCO Company introduced a new acoustical smoke vent that provides the highest level of protection against exterior noise intrusion. Photo: The BILCO Company
THOMAS RENNER writes on building, construction and other topics for U.S. trade publications.
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may 2020
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