The loud thwap-thwapping of a helicopter can wake you up in the middle of the night or force you to close the front door in the middle of a summer hot spell.
To many longtime residents, particularly in areas of increased crime and poverty, the sputtering of a chopper signifies something bad happening nearby. In these cases, the sound can last a quarter hour or more. In others, the sound is simply a passing nuisance.
But noise of any sort, at the right level and persistence, can pose a significant risk to our physical and mental health. Over the next few days, we'll be exploring how helicopters fit into the overall soundscape of our city, what risk they pose to our health, and whether there is anything to be done about it.
The Trouble with Noise
In addition to loss of concentration at the least and hearing loss at the worst, noise exposure in a workplace or classroom setting can cause behavioral changes and problems with self-confidence and irritation, according to the World Health Organization.
Noise can also affect mental health and has been implicated in producing stress-related health effects such as strokes, ulcers, heart disease and high blood pressure, according to the "Noise Effects Handbook," published in 1979 by the U.S. Environmental Protection Agency.
"Excessive annoying noise may be detrimental to public health," explains Robert Vasquez of the L.A. County Department of Public Health. "We have set standards to address excessive noise."
About 40 times a year county staff sets up monitoring equipment outside residences to address noise complaints. If anything is making a sound above 50 decibels during the day or 45 at night for more than 30 minutes in an hour, they will make it stop. Vasquez almost always solves the problem, most often caused by air conditioners, public address systems, fisherman at the harbor, without ever issuing a citation--he just works with the person or business creating the disturbance.
There's only a five decibel difference between what's allowed at night and day because "five decibels is significant," Vasquez said.
To put things in perspective, a sound level of 75 decibels--almost as loud as an alarm clock two feet away--will cause 37 percent of the population to be highly annoyed and a conversation would be unintelligible. At that level, noise is likely to be the most important of all adverse aspects of the community environment, according to the EPA's noise handbook.
Decibels increase exponentially. An increase of just three decibels doubles the acoustical energy emitted, according to the San Francisco Department of Public Health, where officials estimate that 1 in 6 are at risk for health problems due to annoyance, anxiety and sleep problems because of traffic noise.
Helicopter noise, although less persistent, is similar to the noise from traffic. A helicopter flying around 500 feet, the lower end of the altitude regularly flown by LAPD choppers, has about the same volume as the typical noise from traffic in a big city.
The LAPD's AStar helicopter, an intermediate-sized craft, produces about 87 decibels at 500 feet.
Of course, the county gets a lot of complaints about jets and helicopters. But those, Vasquez said, are "under the FAA."
Next: Part 2, FAA Regulations
This series on helicopter noise is brought to you by Spot.Us, with contributing support from the California Endowment and KCET. Eddie North-Hager runs a news & social network for a number of L.A. neighborhoods, including Leimert Park.