When concert-goers spend big money on tickets to hear America's latest idols perform on stage, they expect to hear top-quality vocals ? without a generator humming in the background. Some entertainment events and film productions, along with live broadcasts, require the rock star performance of a generator with an incredibly low-noise level, under 50 dB at 50 feet, (and, of course, a higher price).
But for most rental applications, about 70 dB to as few as 58 dB at about 23 feet will meet a customer's sound attenuation needs for diesel-powered towables. Gasoline-powered portables ranging from 3 kW to 15 kW will be noisier, closer to 72 and 74 dB at about 23 feet, because they do not have an enclosure, or housing, according to Chris Habic, co-owner of Gillette Generators, which is known for its large assortment of portable generators. For that reason, he says sound attenuation, or sound reduction, really comes into play starting at about 15 kW.
The rental house that can offer its customers a quieter generator will have a competitive advantage, says David Dahlstrom, director of sales and marketing for Shindaiwa Inc., which is known for its Kwiet Power brand diesel generators ranging from 20 to 150 kW. The more quiet a generator is, the more useful it becomes for different applications, from powering a county fair midway or a local band concert to meeting the changing needs of today's contractors.
"What makes a piece of equipment good for a rental company is one that has a lot of utilization," says Todd Howe, Doosan Infracore Portable Power product marketing manager for generators. Doosan Infracore Portable Power's full line of Ingersoll Rand PowerSource mobile generators provides power ranging from 10 kW to 450 kW.
Howe estimates about 80 percent of its gasoline-powered portable and diesel-powered mobile generators start their life in the rental environment.
"We're finding the trend with rental companies has been to go to quieter and quieter sound levels to increase the versatility and utilization of the product."
Local noise control ordinances have helped encourage this trend. An ordinance in Montgomery County, MD, is one example. Between the hours of 7 a.m. and 5 p.m., Monday through Friday, noise from construction activities must not exceed 75 dBA, measured at the nearest receiving property line (the receiving property is any property where people live or work and where noise is heard), but no less than 50 feet from the source. Several construction activities, such as demolition or pile driving, might inherently exceed 75 dBA, depending on the circumstance. In those cases, the ordinance allows up to 85 dBA, provided a Noise Suppression Plan, approved by the Department of Environmental Protection, is implemented. At times other than 7 a.m. to 5 p.m. weekdays, construction activities must meet the residential standard of 65 dBA during the daytime and 55 dBA at night, and non-residential standards of 67 dBA during the day and 62 dBA at night. Among the tips that the county offers contractors for complying with the noise ordinance is "when renting, specify the quietest equipment available. Low noise equipment is often of better quality and durability."
Local ordinances will usually vary from one community to another. At night, when generators might be needed to run dehumidification equipment, lights or submersible pumps, for example, noise ordinances are usually stricter. Typically there are more noise restrictions in more populated, urban areas. Hospitals and schools also can have noise restrictions (that primarily impact standby units, not rentals during power outages).
On a jobsite, Habic points out the generator is not usually going to be the largest producer of sound. Air compressors (regulated to 76 dBA by the federal Noise Emission Standards for Construction Equipment), cement trucks and excavators breaking up concrete, for example, will be louder.