Environmental users were looking for levels and sound recording of concern to them, or populating complaint management apps issued by councils, for example. Internal or External Microphone? The question of how accurate, for want of a better description, a noise measurement app could be using an internal microphone has been discussed at length. The most significant differences were shown when the noise contained a high proportion of low frequency content or where the measured noise contained a significant impulsive component not uncommon within a manufacturing environment.
Free Decibel Meter app for iPhone
Environmental users were looking for levels and sound recording of concern to them, or populating complaint management apps issued by councils, for example. Internal or External Microphone? The question of how accurate, for want of a better description, a noise measurement app could be using an internal microphone has been discussed at length.
The most significant differences were shown when the noise contained a high proportion of low frequency content or where the measured noise contained a significant impulsive component not uncommon within a manufacturing environment.
Another recent test of an sound level meter app using a new iPad showed a discrepancy of up to 10dB between measurements. This appeared to be caused by the use of multiple microphones on a device, especially where one or more of the microphones is being used automatically for noise cancellation.
This effect was more pronounced at low levels below 40dB A where this could significantly impact upon environmental noise measurements and calculations where the statistical distribution of the noise is an important metric.
Positioning of the Device The orientation or positioning of the device has been shown in previous studies to be a significant factor upon the frequency response of the measurements. Some devices now use multiple microphone capsules spread over the body of the device to allow for noise cancellation, enhancing the quality of speech. The location of the microphone on tablets is more variable as these are not intended to be used for calls. Most modern devices will auto-rotate the display as the user moves the phone with the result that the microphone could possibly be in one of four different positions.
A quick sample of users of smart phones and tablets showed that unless that were made aware of the position of the microphone they would hold the device with the microphone typically facing their body, sometimes with the body of the device touching their clothing, further affecting the frequency response of the device. Standards, Consistency and Repeatability The big question is whether this type of sound level meter app could, or should, be used where there is a requirement to meet a standard or regulation.
The standards, regulations and guidelines to which most of us are working will specify that an instrument should meet Class 1 or Class 2 of this standard.
Other sound level meter apps have similar statements or none at all. What is Being Measured? An evaluation of 25 sound level meter apps on the Google Play Store showed that only 6 labelled the metric being displayed correctly. Where some form of averaging was available, only 8 of the sound level meter apps used displayed Leq or TWA as a metric. The others used Average or Mean as a descriptor. The clear risk here is that the user may not be aware of whether the app is providing the appropriate metric or whether the processing of raw data to provide those metrics is correct.
The sound level meter app is showing 61, 76 and 39 respectively but with no indication as to the applied time and frequency weighting. This is not a judgement on a specific app but an example of how the information displayed could be misleading. Sound Level Meter Apps — Conclusion The aim of this is not to approve or disapprove of the use of sound level meter apps. There are plenty of apps that, when used with the appropriate microphone, can be an effective and accurate way to take measurements.
However, we a significant proportion of the users could be at risk of using inappropriate equipment to take what could be business critical measurements.
Education and information is key.
Sound Meter (Noise & Decibel)
Note the loudness of a sound also depends on your distance from the source of the sound it will get quieter as you get farther away —so to do a direct comparison of different sounds, you have to keep this distance constant. What does all this have to do with a smartphone?
VIDEO: Free Db Meter App
NIOSH has released a free smartphone sound measurement app for Additionally, a Larson-Davis Model type 1 sound level meter was. Of the apps tested, researchers determined that some of the Apple apps had sound level measurements within plus or minus 2 dBA, which falls within national standards NIOSH adds stepladder safety to free app.
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