Product Overview
The G.R.A.S. Microphone Type 40BH is a ¼-inch high-pressure microphone designed for measuring acoustic impulses and very high sound-pressure levels up to 194 dB. It features a flat pressure-frequency response from 10 Hz to 20 kHz, making it suitable for sound pressure and impulse-sound measurements.

Specifications

• Frequency Response: 10 Hz - 20 kHz ± 2.0 dB
• Nominal Sensitivity: 0.4 mV/Pa
• Polarization Voltage: 200 V
• Dynamic Range: Upper limit of 194 dB re. 20 µPa with 3% distortion
• Microphone Thermal Noise: 60 dB re. 20 µPa
• Capacitance: 6 pF
• Temperature Range: –40 °C to +150 °C
• Dimensions: Length/Diameter with protection grid: 10.5 mm/6.9 mm; without protection grid: 9.1 mm/6.3 mm
• Weight: 2g
• Humidity Range: 0 - 100% (non-condensing)

Design and Construction
The microphone is constructed from non-corrosive, stainless materials to withstand rugged handling and corrosive environments. It is rear vented, which is advantageous for applications where phase response is critical.

Compliance and Warranty
All G.R.A.S. microphones comply with IEC 1094 standards for measurement microphones and are guaranteed for 5 years. Each microphone is individually checked and calibrated, with a calibration chart provided.

Additional Information
G.R.A.S. offers compatible ¼-inch preamplifiers for use with the Type 40BH. The microphone's mounting thread is compatible with other similar preamplifiers. Free-field corrections for various angles of incidence are provided, with 90° incidence recommended for free-field measurements.