I’ve been experimenting with browser-based sound measurement tools recently, and I’ve found similar challenges around calibration and device variability. It’s interesting to see how close some apps can get to real meters when calibrated properly.

Thanks for sharing such a practical breakdown!

https://www.checkhearing.org/soundmeter.php

https://youlean.co/online-loudness-meter/

The NIOSH Sound Level Meter (SLM) app for iOS devices can be used by safety and health professionals and industrial hygienists to assess risks, similar to how they would use a professional sound level meter, and by workers to make informed decisions about the potential hazards to their hearing in the workplace. The app allows the user to acquire and display real-time noise exposure data and help promote better hearing health and better prevention efforts. Read and comment about the app on our science blog:

https://blogs.cdc.gov/niosh-science-blog/2017/01/17/slm-app/

Free Sound Level Meter App from CDC’s National Institute for Occupational Safety and Health
https://www.noisyplanet.nidcd.nih.gov/have-you-heard/cdc-niosh-app

Do you work in or near a noisy environment, such as a construction site, a popular restaurant, or a concert or sports venue? Ever wonder how loud the noise really is and if it could be damaging your hearing? There’s an app for that!

The National Institute for Occupational Safety and Health (NIOSH), part of the Centers for Disease Control and Prevention (CDC), developed the NIOSH Sound Level Meter (SLM) app for iOS devices to help promote better hearing health and prevention efforts. You can download the free app
on iTunes.

NIOSH estimates that 22 million workers in the United States are exposed to hazardous noise levels each year. The SLM app can help you prevent permanent hearing loss caused by noise—a problem that can occur immediately or over time.

For example, NIOSH SLM reports the sound level in different weighted decibels, including A-weighted decibels, which can give you a good idea of the level of sound that could harm your hearing.

NIOSH Sound Level Meter App
https://www.cdc.gov/niosh/topics/noise/app.html

NIOSH Sound Level Meter App
Close-up of downloaded Sound app.

The NIOSH Sound Level Meter (SLM) app combines the best features of professional sound levels meters and noise dosimeters into a simple, easy-to-use package. The app was developed to help workers make informed decisions about their noise environment and promote better hearing health and prevention efforts.

Key Features

Developed by experienced acoustics engineers and hearing loss experts.
Tested and validated (accuracy ± 2 dBA) according to standards in a reverberant chamber at the NIOSH acoustics lab – the only proper method to validate accuracy.
Meets Type 2 requirements of IEC 61672:3 SLM standard when used w/ external microphone.
Provides the most relevant metrics found in professional sound instruments today. Averages such as LAeq and TWA, Max and Peak Levels, Noise Dose and Projected Dose according to NIOSH and OSHA standards, and all three major weighting networks (A, C, and Z).
Capability to calibrate either internal or external microphone. Reporting and Sharing data.
Up-to-date informational screens on what noises are considered hazardous, how to conduct a noise measurement, how to properly select a hearing protector, and guidelines for preventing hearing loss.
Technical support available directly from NIOSH hearing experts.

You’re bringing the grandchildren to see your favorite professional sports team take on the league leaders. Will the roar of the crowd be enough to warrant wearing ear protection? Or maybe you’ve hired a local band to play outside at your daughter’s graduation party. Is the music too loud for your guests and the neighbors?

It’s the latest in instrumentation for the well-appointed shop — an acoustically coupled fast Fourier transform tachometer. Sounds expensive, but it’s really just using a smartphone spectrum analyzer app to indirectly measure tool speeds. And it looks like it could be incredibly handy.

https://www.youtube.com/watch?v=xutm6oMTBw8

As of June 2013, 60% of all mobile subscribers use smartphones—that’s more than 140 million devices. Apple iOS and Google Android platforms account for 93% of those devices

NIOSH noise researchers received numerous requests from stakeholders, safety professionals, and the public to address the accuracy of the many sound measurement applications available for smartphones and whether they can be relied upon to provide an accurate assessment of the ambient environment. As a result, we conducted a pilot study to select and characterize the functionality and accuracy of these apps as an initial step in a broader effort to determine whether these apps can be relied on to conduct participatory noise monitoring studies in the workplace [Kardous and Shaw, 2014]. The resulting paper, Evaluation of smartphone sound measurement application, was published in the Journal of the Acoustical Society of America.

Overall, the results in Figure 2 show that for A-weighted sound level measurements three apps had mean differences within ± 2dBA of the reference measurements. For un-weighted sound level measurements three apps had mean differences within the ± 2 dB of the reference measurement. Since national standards and occupational guidelines specify that type 2 sound measurement instruments have an accuracy of ± 2dBA, some of the above-mentioned apps could potentially be used in the occupational setting, especially if they’re used in conjunction with a type 2 external microphone such as the MicW i436.

November 2016 Update: NIOSH researchers have just published a follow-up study: Evaluation of smartphone sound measurement applications (apps) using external microphones to examine the performance of sound measurement apps using external microphones. The study showed sound level measurements to be within ±1 dB of the reference system using the same test setup and apps from the initial study.