GRAS 46BC multifield microphone
46BC is a true multifield microphone for use in pressure, free-field, or random-incidence environments or any scenarios where the sound field is ill-defined or changing. The design of this microphone takes advantage of the microphone\'s small dimensions and slightly enhances the high-frequency content, which results in the perfect microphone for in-cabin measurements or any scenarios where measuring in a random incidence environment is needed.
Sound fields have historically been defined in microphone standards as pressure, free field, or random incidence. Multifield microphones can accurately measure in any field or in any combination of the defined fields.
In all situations, sound fields, and angles of incidence, 46BC is compliant with IEC 61672 Limits.
46BC protection grid
Unlike other ¼″ microphones, 46BC is optimized for use with the protection grid. This feature ensures protection during in-cabin measurements.
NOTE: The protection grid creates a resonance that will occur around 35 kHz. This resonance is in the order of magnitude of + 6 dB.
Microphone set concept
Data safety is highly important because the costs related to unsuited and unreliable sensors may determine whether your project turns into a success or not.
For users, data safety translates directly into tools that allow for easier microphone selection, simple system configuration, and reduction of measurement errors.
The microphone set concept. It is simple, reliable, and robust and consists of a microphone cartridge and preamplifier combination, which is calibrated as one unit. This eliminates errors because there is only one sensitivity value to account for and the risk of contaminating the interface is eliminated. Combine this with our unique and proven design and you have the most reliable measurement microphone sets available in the industry today.
Typical applications and use
The small size and optimized frequency response make 46BC ideally suited for applications where the sound field is ill-defined or changing. This is due to the combination of size and optimization, which reduces the influence of angle of incidence of source positions and reflections. The result is a reduction in measurement uncertainty in applications such as in-cabin noise, architectural acoustics, and outdoor measurements. GRAS 46BC is also well suited for general acoustic measurements where high sensitivity and low noise are required.
In-car acoustic measurements
The AES Technical Committee on Automotive Audio [TC-AA] has developed some very useful guidelines for In-car Acoustic measurements in a whitepaper from 2023.
This paper is focused on measurements with microphones in the driver and passenger seat, both on methods and instrumentation.
The RA0399 holder is specially designed to meet the specification in the whitepaper.Together with the GRAS 46BC high sensitive microphone ( or the high sensitive pressure microphone 46BL-1)set, it fulfills the complete test demands in the white paper.
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Find more information on the RA0399 H-shaped holder for 6-unit microphone array
NOTES:
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To achieve optimal performances 46BC must be powered on for at least two minutes before starting a measurement.
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Unlike other CCP microphones, a positive pressure on the 46BC diaphragm generates a negative output voltage.
Compatibility
To perform as specified, the GRAS 46BC microphone set requires a constant current input module that can deliver 3.5 mA and 24 V unloaded CCP voltage supply. If the constant current supply is lower, the capability of driving long cables is reduced, and consequently, the upper frequency is reduced. If the voltage supply is lower, it will influence the upper dynamic range.
The microphone set is terminated with a 10/32 Microdot female connector. Ready-to-use coax cable assemblies of various types and lengths are available in standard as well as customized lengths.
The 46BC is IEEE 1451.4 TEDS v. 1.0 compliant. If your measurement platform supports Transducer Electronic Data Sheets (TEDS), you will be able to read and write data like properties and calibration data.
System verification
The functionality of TEDS is very useful to determine which microphone is connected to which input channel. However, it is not a check of whether the microphone is within specifications or not. For daily verification and check of your measurement setup, we therefore recommend using a sound source like the GRAS 42AG Sound Calibrator.
For proper sensitivity calibration we recommend using a reference sound source like the GRAS 42AP Intelligent Pistonphone.
Calibration
46BC has a diaphragm that is slightly larger in diameter than is standard for ¼″ microphones. This does not affect sensitivity calibration, but for frequency calibration, you need a RA0236 Adapter.
When leaving the factory, all GRAS microphones have been calibrated in a controlled laboratory environment using traceable calibration equipment. Depending on the use, measurement environment, and internal quality control programs we recommend that the microphone is recalibrated at least once a year.
We offer two kinds of calibration as an optional after-sales service: GRAS Traceable Calibration and GRAS Accredited Calibration.
GRAS Traceable Calibration is a traceable calibration performed by trained personnel under controlled conditions according to established procedures and standards. This is identical to the rigorous calibration that all GRAS microphones are subjected to as an integral part of our quality assurance.
GRAS Accredited Calibration is performed by the GRAS Accredited Calibration Laboratory that has been accredited in accordance with ISO 17025 by DANAK, the Danish Accreditation Fund.
If you want a new microphone set delivered with an accredited calibration instead of the default factory calibration, specify this when ordering.
Learn more at calibration.
Quality and warranty
GRAS microphone sets are made of components from our proven standard portfolio and are all manufactured of high-quality material and branded parts that were chosen and processed to ensure life-long stability and robustness.
All parts are manufactured and assembled at the factory in Denmark by skilled and dedicated operators in a verified clean-room environment. The microphone diaphragm, body and unique protection grid are made of high-grade stainless steel and make the microphone set resistant to physical damage as well as corrosion caused by aggressive air or gasses.
This, together with the enforced gold-plated microphone terminal, guarantees a highly reliable connection. Thanks to the high quality, our warranty against defective materials and workmanship is five years.
Service
Should you by mistake damage the diaphragm on a GRAS microphone we will in most cases be able to exchange it at a very reasonable cost and short turn-around time. This not only protects your investment but also meets your quality assurance department since you do not have to worry about new serial numbers etc.
