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Bruel & Kjaer Mouth Simulator Type 4227 is an accurate reference sound source developed for near field testing of telephone transmitters and microphones. It provides a standardised and realistic simulation of the human voice field. Features Conforms to IEEE-269, IEEE-661 and ITU-T P.51. Accurate level and frequency response calibration is easily done using a Brⁿel & Kjµr ╜ microphone placed in the supplied calibration jig Accurate simulation of human voice field Quality control testing of frequency response and distortion of telephone transmitters and close-talking microphones Continuous SPL of 100dB 25mm from lip ring Low distortion Built-in overload protection circuit