Every 10 dBA increase is perceived by human ears as a doubling to tripling of the sound level. In contrast, a dB (without the "A") level is the actual sound intensity level, where sound intensity levels double every 3 dB. But the human ear only perceives the sound level change, not the intensity, depending on frequency, masking, bandwidth, and habituation to ambient sound levels. Therefore, the dBA weighted scale is usually used to measure sound levels. dB is used to measure intensity levels, which the ear cannot accurately judge. But the intensity level will affect human health and can cause damage to ears when higher than 85-90 dB.
What Is The Difference Between dBA and dB?
I measure sound levels with a portable meter, measured in dBA, a logarithmic weighted scale of sound pressure as perceived by human ears.
Silence - The Absence of Noise
The sounds of silence
Where there's no noise of man
Motors, engines, cars and trucks
Birds, squirrels, insects, winds and water
An explanation of noise and sound levels, and listing of quiet places found in my travels through the rural countryside, and in city, county, and other parklands around Hendry, Lee, Collier, and Glades county, Florida.
For several years I've tried to find quiet locations where human-made sounds, especially machine noises, are minimal in the natural soundscape.
These levels of noise are considered those which will permit spoken conversation and other activities such as sleeping, working and recreation, which are part of the daily human condition.
The baseball and football park south of Cowboy Way are also very quiet, especially in the summer when they are little used. The sound level was 40-42 dBA at the picnic tables under the trees in the center of the park. Distant vehicle traffic could be heard and cicadas in the oak trees.
Another surprisingly quiet place is the LaBelle Municipal Airport south of Cowboy Way, east of SR29. When airplanes are not in operation the sound level is 42-45 dBA at the picnic table at the office. However, a single engine Cessna 172 taxied by at 20 feet raising the sound to 75 dbA. When the small four seater took off 350 feet away, the sound measured 81 dBA. When planes are not operating the airport is a very quiet place.
How Loud Is Too Loud?
dBA measurements are sound intensity levels adjusted to frequencies most sensitive to a healthy human ear, measured in decibels, a logarithmic scale. 30 dBA is the loudness of whispering. 60 dBA is the loudness of normal speaking, or the sound of a bath shower.
The Environmental Protection Agency identifies a 24-hour exposure level of 70 decibels as the level of environmental noise which will prevent any measurable hearing loss over a lifetime. Likewise, levels of 55 decibels outdoors and 45 decibels indoors are identified as preventing activity interference and annoyance.
Quiet parks in the city of LaBelle are not easy to find. The new recreation park on Cowboy Way west of the LaBelle Elementary school is surprisingly quiet with a sound level of 43-44 dBA at the picnic shelter. Measured at 11 a.m. Wednesday July 22, 2009 the only sounds were a distant machine north of the park and a city maintenance person mowing the grass at the south end. Cicadas could be heard coming from the oak trees in the park.
What may be the quietest location in Hendry County, Florida is on Church Rd. at the Townsend Canal in southwest Hendry. 32 dBA was measured at 11 a.m. Saturday, July 18, 2009.
The only sounds that could be heard was orange grove machinery miles to the south. Jet plane noise far overhead could also be heard but did not raise the sound level, although a small plane overhead raised it a few decibels. A vehicle passed about every five minutes raised the sound level to about 70 dBa for a half minute.
The Occupational Safety and Health Administration (OSHA) says one in a workplace can listen to a 90 decibel (dB) sound for 8 hours straight without any hearing damage. 90 dB is approximately as loud as a busy city street. Ear plugs should be worn whenever sound is over 85 to 90 decibels most experts agree.
At 115 db you can only listen for 15 minutes without hearing damage. One NASCAR race car can be 130 db.
Every sound level 3 dB greater than another doubles the actual sound intensity, but the human ear cannot accurately judge the doubling in strength. A sound 10 dB greater than another is ten times the sound intensity, and because dB is a logarithmic scale, a sound level 50 dB greater is 100,000 times more intense.
The danger of higher sound intensities is that our brain perceives a 10 dB loudness increase as only two to three times louder, when it is actually ten times louder in intensity, and lulls us into a sense of non-danger although the 10 times increase in intensity is causing physical damage to our ears and bodies.
A dBA weighted average sound level is therefore usually used to show the perceived loudness by the human ear in the range between 1000 and 6000 hertz. (A 'C' weighted scale can measure sound levels primarily in a lower range.)
How Loud Are Common Noises?
87 dBA is as loud as a small lawnmower. My 50cc (5 hp) motor scooter measures from 65 dBA at idling speed to 83 dBA at full speed at ear level. To prevent ear damage, ear protection should always be worn around sounds reaching those levels. I use either foam ear plugs or AAA battery operated Panasonic RP-HC55 noise cancelling earphones, which cuts perceived noise about in half.
100 decibels is the equivalent of a pneumatic drill sound.
120 to 130 decibels is as loud as the front row of a rock concert with 200 huge speakers. 127 will cause tinnitus, ringing in the ears.
Race Track Levels: NASCAR race cars can be 130 db for one car. Add 43 cars in a race and the sound bouncing off grandstands and you are in a dangerous position without ear protection. A Formula 1 race car with 700 h.p. can be 147 decibels. And 163 decibels for N.H.R.A 7,000 h.p. dragster at 50 feet.
Some sports car tracks disqualify cars that exceed certain sound levels because of the sound level danger involved for drivers, employees, and spectators when several cars are on the track. From Com Sports Car Forum, in 2010 maximum levels allowed for various sports car tracks (cars at full throttle on straight track):
NHMS: 99 dB @ 50ft
Mont Tremblant: 92 dB
Mosport: No limit
Summit Point: 103dB @ 50ft
Lime Rock Park: 89dB @ 50ft
Calabogie: 92dB @ 50 ft
Watkins Glen: No limit
Add more than one race car passing you and the sound increases accordingly.
Colorado Health Department letter to a sports car race track developer regarding high sound levels
To measure sound levels a portable sound level meter is used. I measure dBA pressure with an Extech Model 407762 professional meter which reads down to 30 dBA. Radio Shack sells a quality meter inexpensively that goes down to 50 dBA for about $20 but is not sensitive enough to measure really quiet places. A search on eBay will turn up meters that go down to about 30 dBA which is quite adequate for measuring most places in which you might encounter silence.
Another quiet place is Port LaBelle in western Hendry county at the end of Helms Road at the southern end of Port LaBelle, which dead ends at a large pasture. Not many vehicles travel out this far and only a few homes are here, about a mile away.
Usual sound readings are about 38-40 dBA in the summer and quiets considerable in the winter when cicadas are not humming to about 33-36 dBA. The only natural sounds heard here are birds flying insects, and cicadas. But, the LaBelle area has jet aircraft flying high overhead at about 10,000 feet on the way to land at Southwest International Airport that does interrupt the quiet here slightly for a few minutes at most local locations expecially in the midday hours. Lower flying smaller aircraft can also be heard flying overhead with equal frequency and at a slightly highe noise volume compared to the jets.
Not So Quiet Parks
Most public parks seem to be located in some of the noisiest places imaginable. The new Veteran's Park in downtown LaBelle across from the courthouse on State Road 80 and State Road 29 would not be bad except for the semi-truck traffic. It had a 53 dBA reading Wednesday July 22, 2009 at 11 a.m. But when a semi-tractor trailer drives by it goes up to 73 dBA.
The small park at Cowboy Way between Bridge Street and Main Street in south LaBelle has several picnic tables, but the sound level is 56 dBA rising to 76 dBA when trucks drive by. You won't hear any nature sounds here.
LaBelle's most scenic park may be Barron Park on the Caloosahatchee River with dozens of giant oak trees and lots of places to sit. At the tennis court bench the level was 45 dBA rising to 60 dBA as trucks passed on State Road 29 about 100 feet to the west.
And a bit to the west of Barron park is the LaBelle Boat Dock where this scenic location reads 47 dBA but rises to 66 dBA as trucks pass over the bridge adjacent.
Highlands County, Florida has several wild rural areas unaffected by man made noise including the Platt Environmental Wildlife Area on Detjens Dairy Road in Venus, Fl. Map Link The sound level July 26, 2009 at 1 p.m. was 34 dBA hearing flying insects and birds.
Collier County, Florida may claim one of the quietest places, outside the Everglades National Park, lying in the Corksrew's C.R.E.W. Environmental Area at N 26 29.289 W 081 31.936. Map Link This is south of Immokalee Road on Corksrew Road in northern Collier county. A convenient bench is placed at this location in this expansive little used park. Lowest sound levels in July 2009 about 1 p.m. were 36-43 dBA. Unfortunately small planes flying overhead and car traffic on rural Corkscrew Road interfered with the bird sounds in the park.
EPA Noise Site - Free coloring book (link at bottom of EPA page)
Glades County, Florida has many quiet places including a 32.5 dBA sound level on a dirt road in the Muse area on county road 731 ( About 4 miles north of the fire tower located at the corner of county road 720 and 731 Map link ) Measured on July 26, 2009 at 11:30 a.m. the only sounds were flying insects and birds. An occassional jet aircraft would be heard high above. Along the dusty road are many cows and commercial pine forests owned by the Lykes Brothers, a major land owner in Glades county.