NIOSH Sound Level Meter

Name: NIOSH Sound Level Meter
Author: US Centers for Disease Control and Prevention

US Centers for Disease Control and Prevention

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Validated with strong research evidence · Supported by multiple studies

For:Researchers & AcademicsGeneral Public & EnthusiastsIndustry Professionals

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App Summary

Developed for workers, safety professionals, and researchers, the NIOSH Sound Level Meter app functions as a professional-grade tool to measure sound levels and assess the risk of noise-induced hearing loss. A series of evaluation studies demonstrated that the app, when paired with a calibrated external microphone, can meet the accuracy and performance requirements for a Type 2/Class 2 sound level meter under international standards. The authors conclude that such smart device-based systems provide a reliable and accessible tool for collecting occupational noise exposure data, helping to identify and control hazardous noise environments.

App Screenshots

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Detailed Description

Functionality & Mechanism

Developed by acoustics engineers at the National Institute for Occupational Safety and Health (NIOSH), the app functions as a mobile sound level meter and noise dosimeter. The system leverages the device's internal or a connected external microphone to capture acoustic data in real time. The interface displays critical occupational noise metrics, including time-weighted average (TWA), LAeq, peak levels, and projected noise dose according to NIOSH and OSHA standards. The system supports A, C, and Z weighting and includes a calibration module.

Evidence & Research Context

A series of evaluation studies demonstrated that when paired with an external calibrated microphone, the app's measurements are accurate to within ±1 dB of a reference Type 1 measurement system.
Validation studies confirmed the app can achieve compliance with most requirements for a Class 2 instrument under the IEC 61672/ANSI S1.4-2014 standard when used with a compatible external microphone.
With the device's internal microphone, the app was validated by NIOSH in a reverberant chamber and demonstrated an accuracy of ±2 dBA.
Associated research highlights that the use of an external, calibrated microphone significantly improves measurement precision and reliability compared to the device's built-in microphone.

Intended Use & Scope

This tool is intended for occupational safety professionals, industrial hygienists, researchers, and employers to conduct preliminary noise assessments and facilitate hearing loss prevention awareness. Its primary utility is for spot measurements and identifying potentially hazardous noise sources. The app is not a direct substitute for certified equipment required for regulatory compliance, which necessitates professional consultation and certified hardware.

Studies & Publications

4 publications

Peer-reviewed research associated with this app.

Validation Study

Smartphone-based sound level measurement apps: Evaluation of directional response

Celestina et al. (2021) · Applied Acoustics

Sound level meter app with external microphone accurately measures sound from different directions.

Smartphones have evolved into powerful devices with computing capabilities that rival the power of personal computers. Any smartphone can now be turned into a sound-measuring device because of its built-in microphone. Many sound measuring apps exist on the market for various mobile platforms. In our earlier research, we showed that a smart device with an adequate app can achieve compliance with most of the Class 2 requirements for periodic testing. In this paper, we present the methods and results of measuring directional response of a sound level meter consisting of a smartphone and one commercially available sound level meter app in the horizontal plane. We used both the built-in smartphone microphone and an external microphone according to relevant IEC [International Electrotechnical Commission] and ANSI [American National Standards Institute] sound level meter standards. The results show that the sound level meter app and an external microphone can achieve compliance with the requirements for Class 2 of IEC 61672/ANSI S1.4–2014 standard in the horizontal plane.

Validation Study

Smartphone-based sound level measurement apps: Evaluation of compliance with international sound level meter standards

Celestina et al. (2018) · Applied Acoustics

NoiSee app with external microphone meets professional sound level meter standards for accuracy.

Smartphones have evolved into powerful devices with computing capabilities that rival the power of personal computers. Any smartphone can now be turned into a sound-measuring device because of its built-in microphone. The ubiquity of these devices allows the noise measuring apps to expand the base of people being able to measure noise. Many sound measuring apps exist on the market for various mobile platforms, but only a fraction of these apps achieve sufficient accuracy for assessing noise levels, let alone be used as a replacement for professional sound level measuring instruments. In this paper, we present methods and results of calibrating our in-house developed NoiSee sound level meter app according to relevant ANSI (American National Standards Institute) and IEC (International Electrotechnical Commission) sound level meter standards. The results show that the sound level meter app and an external microphone can achieve compliance with most of the requirements for Class 2 of IEC 61672/ANSI S1.4-2014 standard.

In the Media

NIOSH App Measures Workplace Sound Levels

NIOSH researchers developed the Sound Level Meter app to collect workplace noise exposure data and help workers make informed decisions about hearing hazards, with plans to use it as a crowdsourcing research tool. "A long-term goal is that this app will become a research tool that people can use for doing workplace surveys," said Capt. Chucri Kardous, a senior research engineer who worked on the app. The app is only available on iOS devices because NIOSH found that Android's fragmented marketplace with hundreds of different device configurations made testing and verification impossible in their laboratory.

AihaRead article

New NIOSH Sound Level Meter App

NIOSH hearing loss researchers collaborated with app developer EA LAB to create the NIOSH Sound Level Meter app that measures and characterizes occupational noise exposure similar to professional instruments. The app met NIOSH testing criteria with "Â± 2 dB mean difference from the reference type 1 sound level meter" and achieved even closer agreement within "Â± 1 dB" when used with external calibrated microphones. The iOS-based app is now available freely on iTunes to occupational safety professionals and the general public.

CdcRead article