Over the past few years there has been a growing awareness of the availability and application of sound level meter apps which provide simple noise measurement functions.
Some of these sound level meter apps have been designed to meet compliance with relevant instrumentation standards when used with a suitable external microphone. But, if combined with the range the range of devices available, there is potential for significant variations in the accuracy, function, and performance of the measurement chain.
So, can convenience and cost efficiency ever override accuracy when it comes to noise measurements?
How widely used are Sound Level Meter Apps?
A significant portion of the noise measurement equipment sold in the UK and overseas is used for the compliance with regulations and legislation.
At Cirrus Research, our team carried out a survey among our customers to see if any of them had used sound level meter apps, and whether they had ever considered the issue of accuracy when it came to these apps.
Our survey found that within Noise at Work, users often used sound level meter apps to make an initial assessment of noise levels or to give other stakeholders a simple way to raise concerns about noise levels.
Internal or External Microphone
The question of how accurate a noise measurement app could be when using a devices internal microphone has been discussed at length. One paper showed that using the same app across a number of different devices (in a controlled environment) gave differences between -28dB(A) and +10dB(A) when compared to a reference sound level meter.
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, like what would be found in a manufacturing environment.
Positioning of the device
Another factor that plays into the accuracy of noise measurement apps is the orientation or positioning of the device.
Most smartphones use a microphone that is positioned at the lower edge of the device where the designers would expect a user’s mouth to be. The location on a tablet, however, is more variable as these are not intended to be used primarily for calls.
A quick sample of users of smartphones and tablets showed that unless they 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.
Most sound level meters currently being manufactured comply with IEC 61672-1, often with the subsequent Type Approval to IEC 61672-2 and then periodic verification to IEC 61672-3. 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.
Can we help?
At Cirrus Research, we provide a wide range of noise measurement instruments to suit all industries and needs, which are easy-to-use and meet relevant regulations.
If you’d like to find out more about noise monitoring, what your business needs to do and how you can fully protect your workers, then get in touch with the noise experts at Cirrus Research, we’re here to help!