Product Overview
The G.R.A.S. Microphone Type 40BD is a ¼-inch precision condenser microphone designed for general-purpose acoustic measurements. It is a prepolarized pressure microphone known for its large dynamic range and wide frequency response, suitable for use in couplers and at boundaries.

Specifications

• Frequency Response: 4 Hz - 70 kHz (± 2.0 dB), 10 Hz - 25 kHz (± 1.0 dB)
• Nominal Sensitivity: 1.6 mV/Pa
• Polarization Voltage: 0 V
• Dynamic Range: Upper limit at 174 dB re. 20 µPa
• Microphone Thermal Noise: 40 dBA re. 20 µPa
• Capacitance: 7 pF
• Temperature Range: -40 °C to +120 °C
• Dimensions: Length 10.5 mm, Diameter 6.9 mm (with protection grid)
• Weight: 2 g
• Humidity Range: 0 - 100% (non-condensing)

Design and Materials
The microphone is constructed from non-corrosive, stainless materials to withstand rough handling and corrosive environments. It is guaranteed for 5 years and comes with an individual calibration chart.

Applications
Typical applications include sound pressure measurements, high-frequency measurements, and high-level pressure measurements. It is compatible with G.R.A.S. CCP 1 preamplifiers.

Performance Considerations
In open sound fields, the microphone's small dimensions minimize disturbances, but corrections are needed at higher frequencies due to reflections and diffractions. Free-field corrections for various angles of incidence are provided.

Compliance and Standards
All G.R.A.S. microphones comply with IEC 1094 standards for measurement microphones.