Uses
- Sound power measurements
- Low-level measurements
- In-cabin measurements
- Measurements in strong magnetic fields
- Homeland security applications
| Features
- Sensitivity 1.1 V/Pa
- Guaranteed noise floor <6.5>
- Slim-line, true ½" solution
- Optimised frequency response up to 20 kHz
- Maximum SPL up to 110 dB
- Connects directly to PULSE and NEXUS front-ends
- Built-in overvoltage protection
- Temperature compensation
- True omnidirectional response
- All titanium construction
- Excellent long-term stability
|
Introduction
Every microphone has an inherent noise caused, amongst other things, by Brownian movements. This results in a noise voltage, which cannot be avoided even with the best microphone.
A microphone with a higher sensitivity will inherently have a better signal-to-noise ratio. That is why some low-noise microphones are 1" types. However, the larger the microphone the more it will disturb the sound field, even at relatively low frequencies.
High quality, conventional 1" condenser microphones such as Brüel & Kjær Types 4144 and 4145 have a typically inherent noise level of 10 dB(A). Together with a high quality preamplifier, such as Brüel & Kjær Type 2669, they provide a combined noise floor of around 11 dB(A), hence a useful measurement range from around 14 dB and up. Similar high sensitivity half-inch types, such as Types 4189 and 4190, allow measurements from around 19 d B(A), and due to their smaller dimensions, cover a wider frequency range – up to 20 kHz. A high sensitivity of the microphone preamplifier system also has the advantage that the noise of the input stage contributes less to the total system noise.
Low-noise TEDS Microphone Type 4955 consists of a high sensitivity ½" cartridge, which has been optimised for the lowest inherent noise.
Description of the Microphone
In order to avoid contamination that would cause increased self-noise, the cartridge-preamplifier is laser-welded and forms one unit. The complete transducer is assembled and adjusted in a clean room environment, guaranteeing low noise over a long period and under critical environmental conditions, such as high temperatures and high humidity. The low-noise preamplifier has a gain of 20 dB and is followed by a carefully designed filter for linearisation of the free-field response of up to 20 kHz. The output stage of the preamplifier has low output impedance and high current-drive capability.
Special precaution has...
For a full Description and Specifications, see 
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