iPhone Screenshots


The NIOSH Sound Level Meter (SLM) app automatically provides a readout of the instantaneous sound level in A, C, or Z weighted decibels using the smartphone’s built-in microphone (or preferably using an external, calibrated, microphone). The weighting is user-selectable and can be accessed from the ‘Settings’ screen. The app also reports the main metrics that are of importance for proper occupational and general purpose noise measurements – mainly the run time (total time), the A-weighted Equivalent Sound Level (LAeq), the Maximum Level measured during the current run time, the C-weighted Peak Sound Pressure Level (LCpeak), the Time-Weighted Average over 8-hour (TWA), and the percentage of the daily noise Dose and Projected Dose. You can select whatever metric to display on the main screen by tapping on that metric. The app contains some basic information on noise and hearing loss prevention. In addition, the app allows the user to save and share measurement data using the smartphone communication and media features. If location services are enabled, the app can utilize the GPS feature to provide general geospatial location of the noise measurement. The app is validated and calibrated for each iOS device at our lab but we recommend that users perform proper calibration using a known noise source or by using an external microphone before and after each noise measurement. Calibration can be accessed from the Settings screen. For additional information, instructional videos, and detailed user guidance and how to interpret the various metrics, please visit the NIOSH SLM app page at: https://www.cdc.gov/niosh/topics/noise/app.html or share your comments on the NIOSH SLM science blog at: https://blogs.cdc.gov/niosh-science-blog/2017/01/17/slm-app/

The app is targeted at safety and health professionals, industrial hygienists, and researchers to use as an initial noise assessment tool, but it does not replace the need for professional instruments or expertise. The app can also be used by workers and the public in general to help make informed decisions about the potential hazards to their hearing, and promote better hearing health and better prevention efforts.

The app was tested and verified for accuracy (± 2 dB) against a reference type 1 Sound Level Meter at the NIOSH Acoustics Laboratory (see NIOSH webpage for links to studies). EA LAB and NIOSH researchers are working towards achieving class 2/type 2 instrument compliance with IEC 61672/ANSI S1.4 Part 3 (Periodic Tests) Sound Level Meter Standards, when the app is used with an external calibrated microphone.

What's New

Version 1.0.7

In this version we have improved iPhone X accuracy and fixed the incorrectly displayed C-weighting for instantaneous parameter.
This version also includes minor improvements and bug fixes.

Ratings and Reviews

4.7 out of 5

638 Ratings

638 Ratings

Well done

Disgruntled albatraoz

I have been using this app for over a year and through several updates. It has always worked well and accurately. It has been a useful tool for monitoring the noise exposure and deciding where and when I need to wear earplugs. The only feature it lacks (in my opinion) is the ability to run as a background process with the phone asleep (similar to the way you can play music), which would allow to have the screen off and use less battery when monitoring for long periods of time. Aside from that personal preference, this app has been reliable and helpful. I would highly recommend it.

It’s more accurate than most apps


It’s more accurate than most apps, but it’s still less accurate than a real decibel meter. It tends to show higher decibel numbers than a real decibel meter would show for a particular noise. For example, it showed 132.6 decibels when I screamed!!! I screamed in front of a RadioShack decibel meter and that only showed 114 decibels.

Developer Response

Thank you for the review, we always appreciate a good feedback, but please note that a scream is hardly the way to measure equivalence or compare the performance of two types of instruments.

BTW, the typical Radio Shack sound level meter is not compliant with any national or international (IEC or ANSI) Sound Level Meter standards, likely has not been calibrated since it was shipped from the factory, and the quality of the microphones used is lower than the quality (frequency and dynamic ranges) than the MEMS microphone in your iPhone.

We tested (and validated) our app with reference to a Type 1 professional quality sound level meter that is compliant with IEC 61672 standard using pink noise over a wide range of sound levels, see this: https://twitter.com/NIOSHNoise/status/822186936093868035

Also, a recent study by EA LAB and NIOSH researchers published in the Applied Acoustics journal https://www.sciencedirect.com/science/article/pii/S0003682X17309945 showed that the app (when used with an external microphone) can meet requirements of IEC 61672:3, something that can't be said about the myriad of consumer type meters on the market today.

Decibel meter


Probably the best you'll get for your phone without plugging in an external microphone, which you can also do with this one anyway.
Like it says it's from NIOSH it's free it has no ads and it's not trying to sell you it's other apps. Download this one.


EA LAB d.o.o.
25.8 MB
Requires iOS 10.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2016 EA LAB


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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