LEVEL ABOVE INDICATOR
Level above indicator/Time above indicator (LAI/TAI)
This device simply activates a relay when the A-weighted
sound level is above some preset level. The A-weighting
should conforms to at least type 2 and the time constant
is 1 sec The initial versions will have two preset levels,
one at 65 dBA and the other at 75 dBA . The preset levels
in follow on versions currently planned will be from 40 dB
to 120 dB in 5 dB steps. The relay will handle up to 120v at
1amps. The purpose of the two main functions of this
product are:
Level above function
The purpose of this device is to provide an inexpensive
method to give feedback to others about a noise problem.
For instance, homeowners near airports can hook one or more
of these devices to Christmas tree lights or some other type
signal. The lights will go on when a plane flew over that
caused noise at a level that is above the preset level.
This allows the homeowner to express displeasure toward the
source of the noise. While designed to measure primarily
aircraft noise, it works well near highways, nightclubs,
outdoor entertainment, construction sites, etc.
Time above function
This device can also serve as a method to quantify the
severity of the noise problem. By hooking up an electric
clock or timer to the output, the amount of time that the
noise is above a preset level can be determined. With this
data, a homeowner can demonstrate changes in the noise
exposure. The amount of time above a certain level is easy
for the average person to understand and should be useful
in court. If the time above the two preset levels is
available, then the FAA approved measures can be estimated.
A draft software program to make these predictions has been
written for the preset levels of 65 and 75 dB and will be
sold at a small cost.
Tentative Specifications
- Size: Approx. 8-cm diameter dome
- Power: 115 v AC
- Operating range: -10 to 50 degree C
- Maximum Fused output: 1 amp at 115 v (may be increased to 6 amps)
- A-weighted accuracy: Type 2 accuracy from 250 Hz to1500 Hz (may attenuate more than weighting above and below this range.
- Accuracy at 1000 Hz: +/- 1.2 dB
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