MEMS measurement microphones

NPL is pursuing the development of MEMS (Micro Electro-Mechanical System)-based measurement microphones. Ultimately, these devices will be:

• Deployable as arrays
• Minimally perturbing
• Robust and inherently stable
• Used for multi-position, long-term monitoring
• Easily deployable and autonomous – can be left measuring whilst unattended
• Less vulnerable to theft
• Multi-parameter sensing (pressure, intensity on 3-axes, others)
• Able to report their positions
• Simple to calibrate with potential for self calibration or internet calibration

Such devices have a large number of applications, including the following areas:

• Environmental noise: measurement, map validation, map construction
• Machinery noise: low-cost arrays, long-term monitoring
• Noise exposure: personal dosimetry
• Condition monitoring

NPL recognised that miniature MEMS microphones, which are available at extremely low cost, represented a potential disruptive technology for the measurement of noise. Therefore, through our research programmes, we have been pioneering their development as measurement devices, together with the underpinning metrology.

The first demonstration of this potential was realised in the DREAMSys project which deployed MEMS microphone based measurement systems in numbers that would not be economically viable with traditional equipment. Systems of up to 40 measurement points were used to validate and augment noise maps around transport infrastructures such as the M25 motorway and London City Airport. Since then, other demonstrator systems have been developed and installed in both indoor and outdoor measurement environments.

NPL has been investigating the potential of commercial MEMS microphones, as measurement grade microphones. This work has resulted in our ability to modify the microphones to yield a frequency response that is compliant with IEC 61672-1 Class 1 requirements.

For more information contact Richard Barham