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.Īndroid-based apps lacked the features and functionalities found in iOS apps. For un-weighted sound level measurements three apps had mean differences within the ± 2 dB of the reference measurement. 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. Figure 2: Differences in A-weighted and Unweighted sound levels between reference system and app measurements by app. Smartphones were set up on a stand in the middle of the chamber at a height of 4 feet and approximately 6 inches from the reference microphone as shown in Figure 1. Additionally, a Larson-Davis Model 831 type 1 sound level meter was used to verify sound pressure levels.
Reference sound level measurements were obtained using a ½-inch Larson-Davis (DePew, NY) model 2559 random incidence microphone. For our experimental setup, we generated pink noise with a 20Hz ‒ 20kHz frequency range, at levels from 65 dB to 95 dB in 5-dB increments (7 different noise levels. The measurements were conducted in a diffuse sound field at a reverberant noise chamber at the NIOSH acoustics testing laboratory.
As a result, a comprehensive experimental design and analysis similar to the iOS devices and apps study above was not possible.
DECIBEL METER ANDROID
A total of 62 Android apps were examined and downloaded, however, only 4 apps partially met our criteria and were selected for additional testing. A total of 130 iOS apps were examined and downloaded from the iTunes store*, of those, 10 apps met our selection criteria. Smartphone apps were selected based on their ability to measure occupationally relevant sound level values. We selected and acquired a representative sample of the popular smartphones and tablets on the market as of June 2013. The resulting paper, Evaluation of smartphone sound measurement application, was published in the Journal of the Acoustical Society of America. 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. 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. Video: CAPT Kardous testing mobile sound-meter apps in the lab However, in order for smartphone apps to gain acceptance in the occupational environment, the apps must meet certain minimal criteria for functionality, accuracy, and relevancy to the users in general and the worker in particular. The use of smartphone sound measurement apps can have a tremendous and far-reaching impact in the areas of noise research and noise control in the workplace as every smartphone can be potentially turned into a dosimeter or a sound level meter. Smartphone developers now offer many sound measurement applications (apps) using the devices’ built-in microphone (or through an external microphone for more sophisticated applications). Apple iOS and Google Android platforms account for 93% of those devices. The SoundMeter app on the iPhone 5 (L) and iPhone 4S (R) compared to ½” Larson-Davis 2559 random incidence type 1 microphone (C).Īs of June 2013, 60% of all mobile subscribers use smartphones-that’s more than 140 million devices. Please share your comments on the related NIOSH science blog post.
DECIBEL METER DOWNLOAD
For more info and to download the app, see the NIOSH sound level meter app page.
DECIBEL METER FREE
NIOSH has released a free smartphone sound measurement app for iOS devices.
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