Measuring the sound from a portable generator helps you understand how much noise it really makes in your yard, at a campsite, or near a worksite. A dedicated sound level meter or a carefully chosen smartphone app can give you useful numbers, but not every tool is built for the task. This guide explains the types of meters, the features that matter when checking generator noise, and what a home user actually needs compared to workplace compliance equipment.
Meter types and accuracy classes
Sound level meters fall into different precision classes. According to the OSHA Technical Manual, Type 1 meters are used for precision field measurements and are considered accurate to within ±1 dBA, while Type 2 meters are general-purpose instruments with an accuracy of ±2 dBA. OSHA notes that the Type 2 meter is the most widely used for workplace evaluations and performs with the minimum level of precision required for its noise measurements.
Meters that do not meet the ANSI standards for Type 1 or Type 2 also exist. OSHA describes these as often modestly priced and useful as pre-screening tools for identifying noisy locations and tracking improvements, but they cannot document compliance with OSHA standards. For a homeowner checking generator noise, a non-ANSI meter can still offer a rough estimate, though its readings may be less consistent.
A NIOSH study published in 2018 examined smartphone sound level meter apps against the IEC 61672 and ANSI S1.4-2014 standards. The researchers found that a sound level meter app combined with an external microphone could meet most requirements for Class 2 of those standards. This means that with the right setup, a smartphone can approach the performance of a general-purpose meter.
Smartphone apps for generator noise
The NIOSH Sound Level Meter app is a free tool developed for iOS devices. The agency’s app page states that it was created to help workers make informed decisions about noise exposure. The app provides A, C, and Z weighting networks, averages such as LAeq and TWA, maximum and peak levels, and noise dose. It can be calibrated using either the internal microphone or an external one, and it allows users to report and share data.
NIOSH explains that the app is only available on iOS because Apple devices share common hardware and software architecture optimized for audio, making it possible to verify performance across all iOS devices. The Android marketplace, in contrast, is fragmented among many manufacturers with different microphone and processing specifications, so NIOSH cannot currently verify the accuracy of an Android-based app in its laboratory.
Safety+Health magazine reported on a 2014 NIOSH study that evaluated over 130 iOS apps and 62 Android apps. Only 10 iOS apps and 4 Android apps met the selection criteria for the trial. The researchers found that some of the Apple apps produced sound level measurements within plus or minus 2 dBA, which falls within national standards for accuracy. The Android apps did not demonstrate the functionality needed for occupational noise assessments. This does not mean all Android apps are inaccurate, but it does mean that without independent verification, their readings should be treated with caution.
An external microphone can improve the accuracy of a smartphone app. The NIOSH study on standards compliance specifically noted that the app and an external microphone together could achieve Class 2 performance. The NIOSH app page also mentions the capability to calibrate an external microphone. When measuring generator noise outdoors, a good external microphone helps overcome the limitations of a phone’s built-in mic.
Features that matter for generator noise
Whether you use a dedicated meter or an app, a few specifications directly affect how useful the reading will be when you are trying to understand generator noise. The table below summarizes each one.
| Specification | Why it matters for a generator | Source |
|---|---|---|
| Type 2 accuracy (±2 dBA) or better | Provides enough precision for general-purpose noise surveys around a generator, helping you compare locations or setups. | OSHA Technical Manual |
| A-weighting (dBA) | OSHA says A-weighted readings are intended to reflect perceived loudness and the effect of noise on hearing; it is the scale generator specs use. | OSHA Technical Manual |
| C-weighting (dBC) | Attenuates low frequencies far less than A-weighting; OSHA notes it is used for low-frequency sounds and for evaluating hearing protection. | OSHA Technical Manual; NIOSH SLM app offers A, C and Z |
| Slow response (1-second time constant) | OSHA notes the meter fluctuates less and is easier to read on slow response in most industrial settings. | OSHA Technical Manual |
| Fast response (125-ms time constant) | Responds faster to changing sound. | OSHA Technical Manual |
| Pre- and post-use calibration | Confirms the meter is reading correctly on the day you use it; for workplace compliance, documented calibration is required. | OSHA Technical Manual |
| Wind screen | Reduces measurement errors caused by wind over the microphone, which is common when checking generator noise outdoors. | OSHA Technical Manual |
The OSHA Technical Manual describes how a wind screen, typically a soft foam cover that fits over the microphone, can be left in place for all measurements. It also protects the microphone from dust, moisture, and incidental contact. When you are outside near a generator, even a light breeze can throw off a reading, so a wind screen is a practical accessory.
OSHA explains that most Type 1 and Type 2 meters can be set to slow response (a 1-second time constant) or fast response (125 milliseconds), and that in most industrial settings the reading fluctuates less on slow response.
Calibration: what a home user needs to know
OSHA’s guidance on calibration is written for workplace compliance officers, but the principles apply to anyone who wants trustworthy readings. The manual distinguishes between periodic factory-level calibration, which manufacturers typically recommend on an annual basis, and pre- and post-use calibration checks done with a portable acoustical calibrator.
For a workplace instrument, annual factory calibration is required, and the calibrator itself must also be calibrated annually. A sticker shows the last calibration date and when the next is due. The manual states that an instrument past its calibration due date must not be used. Pre-use calibration involves placing the calibrator over the microphone, generating a known tone (for example, 114 dB at 1,000 Hz), and checking that the meter reads within the manufacturer’s published limits. If the reading is within about 0.2 dB of the known source, no adjustment is suggested. If fluctuations greater than 1 dB occur, either the calibrator or the meter may have a problem.
A home user checking generator noise is not required to follow OSHA’s documentation rules. However, performing a simple pre-use check with an inexpensive calibrator can catch a low battery or a drifted microphone before you spend time taking measurements. The OSHA manual notes that a low battery is the number-one cause of equipment failing calibration, and changing the battery often brings the equipment back into an acceptable range immediately.
Workplace compliance vs. home use
OSHA’s technical manual is designed for workplace settings. It states that only properly calibrated Type 2 or Type 1 meters can document compliance with OSHA standards. Non-ANSI meters cannot be used for that purpose. For a homeowner, the stakes are different. You are likely trying to compare noise levels at different distances, check whether a new generator is quieter than an old one, or see if a placement change makes a difference. A Type 2 meter or a validated app with an external microphone can serve those needs well.
Non-ANSI meters can give a rough estimate. OSHA describes such tools as useful pre-screening devices for identifying noisy locations and tracking improvements during noise reduction efforts. That description fits the home use case: you can spot-check areas around your generator and get a general sense of the sound levels without needing laboratory precision.
Always put safety first. Never enclose a running generator or block its airflow, and never modify the exhaust or muffler. Only manufacturer-approved accessories should touch exhaust or cooling parts. Always follow the placement rules in your own generator’s manual. Carbon monoxide poisoning is a serious risk, so any noise-reduction strategy must keep the generator outdoors and far from windows, doors, and vents.
Frequently asked questions
Can I use a smartphone app instead of a dedicated sound level meter?
Yes, for non-regulatory purposes. The NIOSH Sound Level Meter app for iOS, when used with an external microphone, can meet Class 2 requirements of the IEC 61672 standard, according to a NIOSH study. Safety+Health reported that some iOS apps produced readings within ±2 dBA. Android apps could not be verified in the same way, so their accuracy is uncertain. For a rough check, an app without an external mic can still be informative, but the numbers may be less reliable.
Do I need to calibrate my meter every time I use it?
Workplace instruments require documented pre- and post-use calibration, as described in the OSHA Technical Manual. For home use, a quick check with a portable calibrator before you start is a good habit. It confirms the meter is working and the battery is charged.
What is the difference between A-weighting and C-weighting?
OSHA explains that the A-network attenuates very low frequencies quite severely and is meant to reflect how noise affects hearing, while the C-network hardly attenuates them and is used for low-frequency sounds and for evaluating hearing protection. The NIOSH SLM app offers both, along with Z-weighting (unweighted).
For more guidance on selecting measurement tools, visit our Noise Measurement Tools category page.
