Figure 1
Decibel meter apps as their publishers describe them
| NIOSH Sound Level Meter (SLM) | NIOSH | iOS only; NIOSH says it cannot currently check an Android app's accuracy | Free to download | A, C and Z | Run time, LAeq, maximum, C-weighted peak (LCpeak), time-weighted average (TWA) and dose | Internal or external microphone | Within ± 2 dBA; meets Type 2 of IEC 61672:3 only with a calibrated external microphone | NIOSH app page and 2017 bulletin |
|---|---|---|---|---|---|---|---|---|
| Decibel X | SkyPaw | Presented as an iOS app; the publisher says it tested and calibrated all Apple devices and many Android devices | Not stated on the publisher's page | A, B, C and ITU-R468 | Current, average (Leq) and maximum; SLOW (500 ms) or FAST (200 ms) response; 30 to 130 dBA | Trim from -15 dB to +15 dB | No figure given | Publisher's app page |
| Decibel Sound Meter | Splend Apps | Android, on Google Play | Free on Google Play, per the publisher | Not stated | Live decibel reading and graph; minimum, average and maximum | Not stated | No figure given | Publisher's apps page |
- SkyPaw,skypaw.com/decibelx.html
- NIOSH,cdc.gov/niosh/noise/about/app.html
- NIOSH,cdc.gov/niosh/bulletin/2017/sound-app.html
- Splend Apps,splendapps.com/apps
How to read these numbers (2)
- Each row paraphrases the publisher's or agency's own page, read on November 3, 2026, with a link to it below; a field the page leaves blank stays 'not stated'.
- The table ranks no app and tests none. NIOSH's accuracy figures come from its own laboratory; the other publishers give no accuracy figure.
The NIOSH Sound Level Meter app
The National Institute for Occupational Safety and Health (NIOSH) publishes its own app, the NIOSH Sound Level Meter, or SLM. Its page says the app is free to download and available only on iOS devices. NIOSH explains the choice: Android phones come from many manufacturers with different microphones, audio chips and software, and the institute says checking the accuracy of an Android-based app is not currently possible.
The app reads A-, C- and Z-weighted levels and reports the measures a professional instrument shows: the run time, the A-weighted equivalent level (LAeq), the maximum, the C-weighted peak (LCpeak), the time-weighted average (TWA) and the dose. It can calibrate either the phone's internal microphone or an external one.
NIOSH states an accuracy within ± 2 dBA, tested in a reverberant chamber at its acoustics laboratory. It also says the app meets the Type 2 requirements of the IEC 61672:3 sound level meter standard only with a calibrated external microphone, not with the phone's own.
How accurate are decibel meter apps?
NIOSH's figures come from its own laboratory. In 2014, its hearing loss team evaluated 192 sound measurement apps for iOS and Android against professional instruments. Of those, 10 iOS apps met its criteria for functions, features and calibration, and 4 of the 10 met its testing criteria.
NIOSH's 2017 bulletin says its own app met the same test, at ± 2 dB mean difference from a reference type 1 sound level meter. With a calibrated external microphone, the app measured within ± 1 dB of the reference over 65 to 95 dB SPL.
Those are lab results over a stated range, not a promise for any phone in any room. The same bulletin adds that no smartphone or smartphone-based app had then met the requirements of sound level meter standards, and that its own app does not comply with any national standard. Neither of the two other publishers in the table gives an error figure for its app.
Decibel X and Splend Apps' meter, from their publishers' pages
Two other apps sat at the top of the results for this search in Google results on November 3, 2026. What follows is what their publishers write, not a test of either.
SkyPaw presents Decibel X as an iOS app, and says it tested and calibrated it for all Apple devices and many Android devices. Its page lists A, B, C and ITU-R468 weighting filters, SLOW (500 milliseconds) and FAST (200 milliseconds) response times, a calibration trim from -15 to +15 dB and a measurement range of 30 to 130 dBA, with current, average and maximum values on screen. It gives no accuracy figure and names no test.
Splend Apps, which lists its apps as free on Google Play, describes its Decibel Sound Meter as using the phone's built-in microphone to show the level in decibels on a live graph, with minimum, average and maximum values. Its page names no weighting, no response time and no calibration setting. OSHA's noise rule reads levels on the A scale at slow response, so a reading with no stated weighting is hard to set beside it.
Setting an app the way OSHA's noise rule measures
OSHA's occupational noise rule, 29 CFR 1910.95, says sound levels are measured on the A scale of a standard sound level meter at slow response. In an app, the matching settings are A-weighting and a slow response, where the app offers them: NIOSH's app offers A, C and Z weighting, and Decibel X lists a SLOW setting of 500 milliseconds.
NIOSH recommends that anyone who wants proper noise measurements use an external microphone that can be calibrated with an acoustical calibrator. It also says its app is not meant to replace a professional sound level meter or a noise dosimeter, or to be used for compliance. A workplace reading that has to stand up to an inspection comes from those instruments, not from a phone.
What a given level means against the federal exposure limits is set out on safe decibel levels, and hearing protectors and their ratings on earplugs.
Frequently asked questions
Can I use my phone as a dB meter?
Yes, for a reading, within limits NIOSH spells out. Its free iOS app is accurate within ± 2 dBA in its laboratory, and within ± 1 dB with a calibrated external microphone over the range it tested. NIOSH says the app does not replace a professional meter or dosimeter and is not for compliance, and that it cannot currently check an Android app's accuracy.
Is there a free app to measure sound decibels?
Yes. NIOSH's Sound Level Meter app is free to download, on iOS devices only; it reads A-, C- and Z-weighted levels and can calibrate the internal or an external microphone. On Android, Splend Apps lists its apps, its Decibel Sound Meter among them, as free on Google Play.
What is the most accurate decibel meter?
NIOSH measures apps against a reference type 1 sound level meter, a professional instrument. For its own app, it reports a ± 2 dB mean difference from that reference, and within ± 1 dB with a calibrated external microphone over 65 to 95 dB SPL. It ranks no other app, and its 2017 bulletin says no smartphone app had then met sound level meter standards.
Does the iPhone have a free decibel meter?
NIOSH's Sound Level Meter app is a free download for the iPhone and other iOS devices. This page read no Apple document on features built into the iPhone, so it does not describe them.
How are decibels measured?
For workplace noise, OSHA's rule measures sound levels on the A scale of a standard sound level meter at slow response. NIOSH's app also offers C- and Z-weighting, and reports the A-weighted equivalent level (LAeq), the C-weighted peak, the time-weighted average and the dose over a measurement run.
Sources
App characteristics are paraphrased from NIOSH's app page and 2017 bulletin, SkyPaw's Decibel X page and Splend Apps' apps page; the measurement rule comes from OSHA's 29 CFR 1910.95; all read on November 3, 2026. NIOSH's accuracy figures are its own laboratory results. No app was tested or ranked for this page, and the App Store and Google Play listings were not used as sources.
Cost and coverage research, not medical advice. A phone app reading does not replace a calibrated sound level meter or dosimeter for a workplace measurement.