Last week we discussed an increase in the use of helicopters in Los Angeles correlated with nuisance complaints regarding loosely regulated helicopter flights. Here, we will review some interesting aspects of noise related to the flight.
According to the Helicopter Association International (HAI), the difference in sound level of a helicopter flying at 500 feet and at 1,000 feet is nine decibels — dropping from 87 dB to 78 dB. That effectively reduces by half the impact of the resultant noise. HAI notes that to meet the generally acceptable criterion of 65 dB, helicopters should fly at altitudes no less than 1,000 feet.
Excessive and annoying noise goes beyond aesthetics and may be detrimental to public health. This is the basis for local and municipal governments noise control ordinances. Local governments cannot prefer the sound of Brahms to the B-52's, only when, where, and at what volume. Noise is the great leveler and while noise is born as a noun, it quickly morphs into an adjective, certainly in our context.
In addition to hearing loss at the extreme and a loss of concentration at the least, noise exposure causes behavioral changes and irritation, according to the World Health organization. According to the Noise Effects Handbook, published by the U.S. Environmental Protection Agency in 1979, noise can affect mental health and has been implicated in producing stress-related health effects such as strokes, ulcers, heart disease, and high blood pressure. In addition, people get really pissed off with an LAPD Bell 206 hovering over their barbeque!
Helicopters rank especially high in causing undesirable noise. Eight different studies have found that the annoyance created by a helicopter does not correlate with the decibels it registers. The helicopter's unique sound, created by blade vortex interaction, causes people to rate its sound level as much as 10 dB's higher than it actually registers, doubling the noise impact. This would place perceived helicopter noise at around 97 dB, or a whopping 30 dB's over the generally accepted noise level of residential areas.
These findings certainly suggest that helicopter flight should be regulated in response to the exceptional levels of noise they produce. Despite the findings on helicopter noise and the aesthetic-health issues linked to excessive, annoying noise, local and municipal legislators have no jurisdiction in this field of noise regulation — leaving us to bemoan our fate, visit a BOSE outlet for noise cancelling headphones, or invest in lead-lined walls and remain indoors.