FAQ
Frequently Asked Questions
A decibel meter is an instrument used to measure sound (noise) levels by measuring sound pressure also called SLM (Sound Level Meter), DB meter (Decibel) or if used for occupational noise, a noise dosimeter.
A typical sound level meter uses a microphone to register the sound, it will be processed by the sound level meter and the value (in dB) will be displayed on the meter.
The decibel is far out the most common unit used to measure and display values of sound. Most other values are derivatives or calculated values from the SPL such as Leq (equivalent sound level), Lmax, (maximum sound level), Lmin (minimum sound level), Lpeak (peak level), dB(A) (A-weighted sound level) and many more.
If the sound level meter is to be used to register sound in a classroom, factory, boundary, music event, road noise etc. then typically an equivalent noise value is required, the PLACID meters have these feature standard build in.
PLACID focusses on Class II instruments (IEC61672 or ANSI S1.4) which for most applications is sufficient.
There are many standards that describe how sound should be measured and interpreted, depending on the application and the country you are living in.
Here below are some examples from typical sound levels in dB(A)
| Description of a sound source | 150 | Eardrum rupture |
| Aircraft carrier deck at close distance | 140 | Very painful |
| Military jet aircraft take-off from an aircraft carrier with afterburner at 10 meter | 130 | Painful |
| Chain saw at 1 meter, blow torch 1 meter | 120 | Painful |
| Steel mill, auto horn at 1 meter. Turbo-fan aircraft take-off at 50 meters, riveting machine, live music near the stage | 110 | Human pain threshold. |
| Jet take-off (at 300 meters), power lawn mower, motorcycle, helicopter at 35 meter | 100 | Serious damage is possible in > 4 hr exposure. |
| Boeing 737 at 1 km distance motorcycle at 10 meters | 90 | Very likely damage in 8-hour exposure. |
| Garbage disposal, dishwasher, average factory, freight train (at 15 meters) | 80 | Accepted as maximum safe level in 8-hour exposure. |
| Passenger car at 100 km/hour at 10 meters, music in the living room, radio or TV-audio, vacuum cleaner | 70 | The arbitrary base of comparison. |
| Conversation in restaurant, office, background music | 60 | Fairly quiet. |
| Quiet suburb, conversation at home | 50 | Pleasantly quiet. |
| Library, bird calls in distance, low limit of urban ambient sound | 40 | Very quiet area. |
| Quiet rural area without any highways, airports, industry, railroads in the vicinity | 30 | Very Quiet. |
| Whisper, rustling leaves | 20 | Barely audible |
| Breathing at distance | 10 | For most people inaudible |
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