A REPEATABLE METHOD
How to use it
- Select the required weighting and time response and record the full indicator, such as LAeq over a stated interval or LAFmax, not just a number labelled dB.
- Fit the windscreen, keep the microphone away from your body and place it at a repeatable height and distance from walls and the source.
- Measure the background with the equipment off, then repeat with one known operating mode active.
- For fluctuating equipment, include a representative operating cycle. Record the start/end time, actual duration, operating mode and background conditions; retain equivalent level and maximum as separate results if supported.
- Repeat in the same position and conditions after any repair, enclosure or speed change.
INTERPRET THE MEASUREMENT
How to read the result
- A change of about 3 dB represents roughly twice or half the sound energy, not twice the perceived loudness.
- A-weighting approximates human sensitivity for many general assessments; low-frequency equipment may also need C-weighted or frequency-band analysis.
- LAeq is an A-weighted energy average over its stated duration; LAFmax is the highest A-weighted Fast-response level during the run, not that average. Slow smooths the display; it does not turn one reading into a whole-run Leq.
- Arithmetic example, not a noise limit: two consecutive 10-minute LAeq intervals at the same position and weighting are 60 and 70 dB. The combined 20-minute LAeq is 10 × log10[(10^6 + 10^7) / 2] ≈ 67.4 dB, not the arithmetic mean of 65 dB. Unequal durations need duration-weighted energies. Do not use isolated display readings or maximum values as if they were interval LAeq, or treat this example as proof of hearing safety or legal compliance.
TROUBLESHOOT THE METHOD
Common problems and what to check
The reading jumps constantly.
Use Slow response or Leq over a stated interval, remove wind and handling noise, and keep the microphone position fixed.
A phone app gives a different value.
Phone microphones, cases and gain control vary. A comparison at one level can reveal an offset, but does not validate frequency response or the full measurement range. Validation of a named app/microphone system is not a certificate for every phone app.
The level is modest but the noise remains annoying.
Look for tonal hum, vibration, impulsive events and low-frequency transmission. One broadband dBA number does not describe every nuisance.
STOP BEFORE THE HAZARD
Safety boundary
- A meter does not protect hearing. Leave hazardous areas and use suitable hearing protection according to local rules.
- Do not reach into running machinery, remove acoustic guards or stand in unsafe traffic or plant areas to improve a reading.
- Legal, occupational and property-boundary assessments require the specified regional method and calibrated equipment.
SMART BUYING GUIDE
What to look for when choosing
- For home troubleshooting, look for A/C weighting, Fast/Slow response, useful low-level range and a standard calibrator fit.
- Leq logging is useful when noise varies over minutes or hours; maximum alone cannot replace an equivalent-level comparison over matched intervals.
- Choose a compliant Class 1 or Class 2 meter only when the project or regulation actually requires it.
Types of tool
Best for: Quick relative comparisons after calibration.
Best for: Household diagnostics and equipment comparisons.
Best for: Logged exposure, environmental and professional surveys.
Common functions
Worth paying more for
- A useful low-noise floor and stable microphone
- Leq logging for variable sources
- Calibration support and the required instrument class
Usually not worth the extra cost
- A professional class for casual before-and-after checks
- Very high maximum range for quiet residential work
- Color displays that add no measurement capability
Sources & instructions
- NTi Audio: LAeq energy averaging, frequency/time weighting and LAFmax
- CDC/NIOSH: sound-meter app metrics and the tested phone/microphone configuration
AI-generated topic illustration; do not use the depicted scale for measurements.