Radio Shack 33-2055, Digital Sound Level Meter, Type II, A-Weighting Slow Response. Displays any SPL over 50 dB(A), or "LO" below 50 dB(A).

Radio Shack 42-3019, Analog Sound Level Meter, Type II, A-Weighting, Fast Response. Displays any SPL over 60 dB(A).

The test set up is in accordance with Jefferson County: 5.90 Noise Abatement regulations.

The digital meter is set for SLOW response and the analog meter is set for FAST response. Since the analog meter only measures 60 dB(A) and above, any meter movement is >= 60 dB(A).

The meters are mounted on a tripod, placed 25ft from the property line in my backyard. Since the trampoline is between our houses, the measurement equipment is actually about 32ft from the trampoline. My house is between the trampoline and the measurement equipment.

A camcorder is used to record both the sound and the view of the SPL meters (not the playground), clearly showing a connection between sounds from the playground and the SPL meter indications. A date/time stamp is recorded on the video recording. The video recording will clearly show a relationship between the playground noise and the high SPL readings. The camcorder audio/video output is fed to an indoor consumer VCR for recording, the camcorder is not recording, hence no possible motor noise to affect the readings.

The decibel (dB) is a measure of sound intensity; that is, the magnitude of the fluctuations in air pressure caused by sound waves. The decibel scale is logarithmic, not arithmetic. This means that a doubling of sound intensity is not represented as a doubling of the decibel level. In fact, an increase of just 3 dB means twice as much sound, and an increase of 10 dB means ten times as much sound.

Decibels are usually measured with a filter that emphasizes sounds in certain frequencies. The "A" filter (dBA) is the one most frequently used (and required by Jefferson County). The "C" filter (dBC) puts more weight on low-frequency sounds such as the bass in amplified music.

The perception of loudness by the human ear is not directly proportional to the decibel level. For example, a sound 10 dB greater than another is not perceived as being ten times as loud but only about three times as loud.

The intensity of noise diminishes with distance.