Measuring generator noise yourself can help you verify whether your unit is as quiet as its specification sheet claims, check the effectiveness of noise reduction steps, or simply understand how loud it is in your own setting. While professional sound surveys use precise instruments and strict procedures, you can get meaningful numbers with a sound level meter or even a well-chosen smartphone app if you follow a few key practices. This guide walks you through the instruments, settings, positioning, and routine that produce repeatable, useful measurements, drawing on workplace noise guidance from OSHA and NIOSH and on generator-industry measurement standards.
Instruments You Can Use
OSHA’s technical manual on noise describes three tiers of sound level meters (SLMs). Type 1 meters are precision instruments with an accuracy of ±1 dBA, while Type 2 meters are general-purpose devices accurate to ±2 dBA. For workplace compliance, OSHA requires at least a Type 2 meter. OSHA adds that other, often modestly priced meters exist that do not meet ANSI requirements for Type 2 or Type 1; they can be useful pre-screening tools to find noisy spots and track improvements, but cannot document compliance.
For a homeowner, a Type 2 meter offers a good balance of cost and reliability (see our noise measurement tools buying guide). A well-validated smartphone app can also work. The National Institute for Occupational Safety and Health (NIOSH) offers a free Sound Level Meter app for iOS devices. NIOSH states that the app, when paired with a calibrated external microphone, meets Type 2 requirements of the IEC 61672:3 standard. A NIOSH study evaluated over 130 iOS apps and 62 Android apps; some iOS apps produced readings within ±2 dBA, while Android apps did not demonstrate the needed functionality (Safety+Health, 2014). A separate NIOSH paper confirms that the agency’s app with an external microphone can achieve compliance with most Class 2 requirements of ANSI S1.4-2014. For trustworthy smartphone-based measurements, use the NIOSH SLM app on an iOS device with a calibrated external microphone.
Key Settings for Generator Noise Measurement
The table below summarizes the settings that matter most. Following it, we explain each choice in more detail.
| Setting | What to choose | Why |
|---|---|---|
| Weighting | A-weighting (dBA) | Matches human hearing; standard for generator specs |
| Response | Slow | Averages noise over 1 second; steadier for continuous sound |
| Microphone orientation | Follow manufacturer (often point at source) | Correct for microphone type |
| Wind screen | Always use | Reduces wind errors; protects microphone |
| Distance | 7 m (23 ft) for spec comparison, or a fixed distance for own tracking | Industry standard; consistency for comparisons |
Weighting. Generac’s white paper explains that A-weighting has become the standard for consumer acoustic measurements because it approximates human hearing sensitivity. Generator specs are published in dBA, so use A-weighting for an apples-to-apples comparison (learn more about decibel levels).
Response. OSHA’s manual notes that slow response uses a 1-second time constant, fast response 125 ms. A generator’s steady noise is better captured with the slow setting, which gives a more stable reading.
Microphone orientation. OSHA advises following the manufacturer’s recommendation: free-field mics point at the source (0°), random-incidence at 70°, pressure at 90°. For most general-purpose meters, pointing at the generator works.
Wind screen. OSHA recommends using the foam wind screen for all measurements to reduce wind turbulence and protect the microphone from dust and incidental contact.
Calibration: Before and After Every Session
OSHA’s procedures require pre- and post-use calibration each day you measure, plus periodic factory calibration (typically annual). Pre-use calibration checks the meter against a known tone (e.g., 114 dB at 1,000 Hz) from an acoustic calibrator. If the reading is within about ±0.2 dB, no adjustment is needed; fluctuations over 1 dB suggest a problem. After measuring, repeat the check without adjusting to confirm the meter stayed accurate. OSHA also stresses making sure batteries will last the measuring session.
While OSHA’s guidance targets workplace compliance, the same principle applies to any careful generator measurement. Follow your meter’s manual; the NIOSH app includes a calibration routine for both internal and external microphones. Calibrating before and after each session gives you confidence in your numbers.
Microphone Position and Avoiding Interference
OSHA’s manual warns that your body can act as a barrier, altering the reading. Hold the meter away from your body, or mount it on a tripod. Keep the microphone clear of hair, clothing, or other objects; the wind screen helps. For workplace measurements OSHA places the microphone in the worker’s hearing zone, which it defines as a 2-foot-wide sphere around the head; for your own generator readings, pick one height and use it every time, and measure from the same side the manufacturer used. Generac, for example, measures residential units from the front panel at 7 meters. Check your generator’s manual for its specific measurement position.
Distance and Making Measurements Comparable
Generac’s white paper states that 7 meters (about 23 feet) is the de facto standard distance for generator sound pressure measurements. Measuring at this distance in an open area lets you compare your reading to the published specification. In a real yard, reflections from walls and hard surfaces will increase the level. Generac provides a free-field formula for estimating level changes with distance: L2 = L1 + 20 × log10(d1/d2). For example, moving from 7 m to 3 m would theoretically add about 7 dB. Use this only for rough estimates because your site is not an ideal free field. For before-and-after comparisons, the key is to always measure from the same spot, at the same distance, and under the same load. Document the conditions. Our placement and distance guide discusses how location affects perceived noise.
A Repeatable Measurement Routine
Here is a step-by-step routine based on the points above.
- Safety first. Place the generator outdoors in a clear area per the manufacturer’s manual. Never operate it in an enclosed space.
- Prepare the instrument. Check calibration status and battery. For the NIOSH app, attach the external microphone if available.
- Warm up and calibrate. Allow the meter to stabilize to ambient temperature (OSHA suggests 5 min per 18°F change). Perform pre-use calibration.
- Set the meter. Select A-weighting, slow response, correct orientation, and install the wind screen.
- Position the microphone. Measure your chosen distance (7 m for spec comparison). Use a tripod at ear height or hold the meter away from your body.
- Run the generator. Let it stabilize at the desired load (idle, half, full). Note the load.
- Take the reading. Allow the slow response to settle, then record. Record the reading once it settles.
- Document. Note distance, side, load, settings, wind, and ambient noise.
- Post-use calibration. Perform a post-use check. If outside tolerance, measurements may be unreliable.
Safety First: Carbon Monoxide and Generator Placement
Always operate the generator outdoors in a location specified by the manufacturer’s manual. Never run it in a garage, shed, or near windows or doors, even for a quick measurement. Carbon monoxide builds up rapidly and is deadly. Do not modify the exhaust or muffler; use only manufacturer-approved accessories. Be aware of hot surfaces and moving parts, and wear hearing protection if you are close to the generator for extended periods.
Frequently asked questions
Can I use my smartphone to measure generator noise accurately?
Yes, if you use the NIOSH Sound Level Meter app on an iOS device with a calibrated external microphone. NIOSH states this combination can meet Type 2 accuracy standards. The internal microphone alone gives a rough estimate. Android apps have not been validated by NIOSH for occupational accuracy.
What distance should I measure from?
The industry standard is 7 meters (23 feet), as described by Generac. Use this distance to compare with manufacturer specs. For personal tracking, any fixed distance works as long as you use it consistently.
Do I need to calibrate my sound level meter every time?
Yes. OSHA requires pre- and post-use calibration checks to ensure accuracy. Even for non-compliance use, this practice keeps your numbers trustworthy. The NIOSH app includes a calibration feature for each session.
For more detailed guidance on measuring generator noise and understanding the numbers, visit our Measuring Generator Noise page. You may also want to explore our Generator Noise Basics section or our Noise Measurement Tools buying guide.
