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Bruel and Kjaer EMS Inc.
Binaural Microphone - Type 4101-A
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Uses
• Binaural sound recording at the entrance to the human ear canal
• Sound recording where a vehicle’s driver wears the Binaural Microphone
• Binaural recordings where the influence of the test-person’s head and torso is important
• Sound recording of a helmeted person, for example, a motorcycle driver
• Psychoacoustic experiments requiring binaural sound recordings on human subjects
• Binaural recordings where the use of a traditional Head and Torso Simulator (HATS), for example, Sound Quality Head and Torso Simulator Type 4100, is impossible
• Evaluation of headphones and ear muffs on a human subject’s head/ears
Features
• Uses miniature, prepolarized condenser microphones that are positioned at the entrance to the ear canal and do not affect normal hearing capabilities
• Very lightweight: < 10 g down to the cable clip with the remaining cable
• Connects to and powered from CCLD input (3 to 10 mA) via a BNC plug
• Free-field and diffuse-field corrections available as an ASCII table and built into the PULSE™ Sound Quality Software Type 7698
• Low equivalent noise level of 23 dB(A)
• Calibration adaptor for Sound Calibrator Type 4231
• TEDS (Transducer Electronic Data Sheet) available
Binaural Microphones Type 4101-A is designed specifically for binaural sound recording where testing on a human subject is preferred, and/or the use of the traditional HATS method is precluded. The microphones are lightweight, do not affect normal hearing capabilities and consequently will not influence test results.
Construction
The Binaural Microphone’s upper section comprises two 2 mm stainless-steel tubes. Because the microphone cables run through the inside of the tubes, either tube can be continuously bent without collapsing, and reshaped to suit test personnel. A miniature coaxial cable in one braid connects Microdot to BNC connectors. Additionally, a cable clip that can be attached to the test subject’s clothing is supplied to relieve pressure on both the microphone’s upper section and the test subject’s ear canal, freeing them from supporting any unnecessary weight or stress exerted by the remaining cable.
The microphone capsules are specially selected versions of the well-proven miniature condenser microphones from DPA Microphones. They are mounted in a gold-plated capsule that is resistant to moisture.
Moulded rubber inserts and windshields, UA-2072, are included so that the ear can be cushioned when Type 4101 is worn under, for example, a crash helmet.
Calibration
The microphones are selected based on matching frequency responses. Operating in the open ear canal of the test person, the Binaural Microphone is calibrated with Head and Torso Simulator Type 4128, which also has an open ear canal.
In a diffuse sound field, the Binaural Microphone is measured for its diffuse-field response mounted on HATS Type 4128. The free-field response at 0 degree frontal incidence is measured in the same way but in an anechoic room. In both cases, the results are averaged over several different mountings of the Binaural Microphone on HATS Type 4128.
The resulting data are shown in the table on page 4 and also included in PULSE Sound Quality Software Type 7698.
Level calibration of the Binaural Microphone when in use, is performed using the special calibration adaptor together with Sound Calibrator Type 4231. Using the adaptor, the output level from the calibrator will be increased by 0.35 dB ± 0.2 dB.
