Some large air-conditioning and heating systems in Charleston are making loud, siren-like drones next to cemeteries, residential areas and parks, a Post and Courier Watchdog survey shows.

A system next to the Francis Marion Hotel sends an ear-splitting whine into an adjacent parking deck at levels similar to an idling bus, according to measurements on a sound meter. The sound echoes into Marion Square, giving the park a constant background hum.

Another heating, ventilating and air-conditioning system next to a Cumberland Street condo building emits a constant wail by the old cemeteries next to St. Phillips Church and Circular Congregational Church.

These machines are part of a trend that experts say has implications for our health and quality of life: The world is becoming a noisier place.

Last year, the International Commission on Biological Effects of Noise compiled studies showing that prolonged exposure to excessive noise can lead to impaired hearing and tinnitus, and can affect heart rhythm and blood pressure. The group also cited studies showing that louder noises make people more aggressive.

In October, the World Health Organization reported that half of the urban areas in Europe endure noise pollution from road, rail and air traffic loud enough to disrupt sleep, impair learning and trigger hypertension at night. The study said that long-term average exposures to noise above 55 decibels can lead to elevated blood pressure and heart attacks.

In the United States, loud motorcycles, car radios and leaf blowers have led to anti-noise ordinances. Earlier this year, Berkeley County passed an ordinance prohibiting noises greater than 65 decibels at night and 70 decibels during the day in residential areas. Charleston County's noise ordinance is less strict and requires that noises in residential areas be less than 80 decibels during the day and 75 decibels at night.

Unlike ordinances in Berkeley and Charleston counties, which set decibel limits, the city of Charleston's noise ordinance has no such decibel trigger. Its ordinance focuses mainly on noisy gatherings, music and vehicles that "disturb the peace and quiet of the city."

North Charleston and Summerville's ordinances are similar to Charleston's.

Some courts have frowned on this lack of specificity. Earlier this year, Virginia's Supreme Court overturned a city's noise ordinance because it was "too vague." The city is asking the U.S. Supreme Court to rule on the issue, which would set a nationwide precedent.

Noisetube, leaf blowers

Excessive noise may rank far behind other environmental and health issues, but that may be changing.

A European team recently set up a Web site called Noisetube.com where people can turn their mobile phones into sound meters and map noise levels in their cities.

Last year, the Tim Robbins movie "Noise" highlighted the story of a man in New York who was so frustrated with car alarms that he broke into cars to turn them off.

Leaf blowers, which produce noise levels from 70 to 90 decibels, are another irritant. In the late 1990s, Peter Graves, Meredith Baxter and other Hollywood stars lobbied for new anti-blower ordinances. More than 20 communities in California have clamped down on loud leaf blowers.

Less attention has been paid to loud heat pumps and other HVAC systems, even though noise from these machines is constant (unlike leaf blowers and radios) and give many Southern cities a background buzz.

With a sound meter, Watchdog measured levels next to several large HVAC units on the Charleston peninsula.

In the parking lot next to the Francis Marion's unit, the decibel meter read 84, which is similar to a lawn mower at five feet or a vacuum cleaner. According to OSHA, 85 decibels can cause hearing damage over time.

The HVAC unit at the Cumberland Street condos measured 75 decibels in the adjacent parking lot, which is comparable to noise inside a B-757 aircraft. Next to the Embassy Suites near the corner of Meeting and Hutson streets, sound levels measured 70 decibels on a nearby sidewalk. At The Citadel, a 58-decibel whine greets visitors as they enter the front gates, and a unit on the other side of campus sends a 60-decibel drone into the neighborhood off Dunneman Avenue.

Other HVAC systems near the Charleston County's Judicial Center generate noise that mingles with the bells of St. Michael's Church, while equipment at the Carolina Yacht Club on east Bay Street competes (56 decibels) with the clip-clop of horse-drawn carriages.

Some sounds are easily heard hundreds of yards away. That's because HVAC units emit low frequency sounds, which travel farther. Sounds travel when particles bump into each other, transferring energy in the process. Sound levels are measured in decibels, with a typical conversation measuring about 60 decibels. Decibel measurements don't go up or down in a straight line. An increase of 10 decibels, for instance, will sound twice as loud. For instance, Charleston County's noise limit of 75 decibels in residential areas is twice as loud as Berkeley's 65-decibel limit.

'Things you can do'

Many variables are involved in sound and its effects, and one person may be annoyed by a sound, while another may not even notice it, said M. David Egan, author of "Architectural Acoustics" and a respected acoustics expert in Clemson. "You have how loud the sound is, its frequency, and the message it conveys," he said, adding that the sound of an office machine might not convey "as frightening a message to some people as say a helicopter."

But, he said, excessive noise often can be reduced. "There are things you can do."

Craig Bennett, a structural engineer with 4SE in Charleston who has worked on several sound-related projects, said many mechanical units around the city are unshielded, "and that can make things tough for neighbors." Enclosing an HVAC unit with a tall wall often helps. "But that's difficult to do in a small site downtown. You need some space around the unit, or you won't get air to it."

Bennett also is chairman of the city's Board of Architectural Review and said the BAR sometimes addresses the noise issue, with a unit's visual impact often being the trigger. "Nobody wants to look at a mechanical unit or a concrete block wall on a rooftop for that matter."

He recalled a resident who wanted to put a unit on a rear roof next to another neighbor's porch, and the BAR rejected the request. He added that residents have more incentive to be respectful in their designs. "Generally commercial and institutional (entities) are concerned with how much it costs and how much it costs to operate," he said. "Frankly, I hear air conditioning units all over the place."

Reach Tony Bartelme at tbartelme@postandcourier.com or 937-5554.