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True Multifield ¼″ High-sensitivity Microphone

GRAS 46BC TransBG04 May 2023 - GRAS Sound & Vibration, part of Axiometrix Solutions, released a new measurement microphone is ideal for automotive in-cabin and NVH testing. The new GRAS 46BC CCP ¼″ Multifield Microphone Set, High Sensitivity is a microphone with a specific set of skills. Focusing on automotive acoustic assessments (from in-cabin speech transmission index to electric vehicle (EV) inverter switching frequency noise), the microphone is designed with all the benefits of small microphones, but also benefits from the low-noise capabilities of its much larger ½″ cousins.

The primary reason that ¼″ microphones had not been used for in-cabin measurements in the past was their noise floor. It was much higher and would miss noise contributors such as road and brake noise, or even the higher frequency contributions that could not be measured by a microphone with a 40 dB(A) noise floor. The high-sensitivity 46BC eliminates this issue. With a noise floor of 24 dB(A), it outperforms all other ¼″ microphones and removes the need for using a variety of ½″ microphones to only come close to the same data quality.

As a ¼″ microphone, its effect on the environment is reduced, and the effect of the angle of incidence from the sound source is minimal. These are challenges for ½″ microphones. They have substantial pressure build-ups in front of the diaphragm, which causes additional challenges in a mix of pressure- and free-field environments and can give under-represented data as the angle of incidence increases. In particular, the 46BC benefits from unique tuning of its response curve to be a truly multifield microphone.

The combination of small-size benefits, multifield tuning, and the lower noise floor of the new GRAS 46BC essentially provide a microphone that is the best of two worlds for automotive acoustic testing.

There is a general trend in measurement to take advantage of ¼″ microphone capabilities, but their noise floors meant they could miss some potentially irritating noise contributions. Developing a ¼″ microphone with a 24 dB(A) noise floor opens up a new range of measurement capabilities—resulting in a better product for end users. —Dr Rémi Guastavino, Director of Product Management

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