Study of frequency properties of infrasound condenser microphone

Distribution of frequency of sensor is studied and influence on amplitude-frequency response is analyzed quantitatively by parameters of different parts of the sensor.The models of the response and its error in cut-off period of the sensor are developed by solving dynamic equation for infrasonic wave field in front and rear chambers.A batch of components with relative error less than 5%of inlets,leaks and diaphragms,and front and rear chambers with relative volume error less than 0.1%are chosen to assemble 32 sensors that are tested by calibration experiment.The calibration results show that the cut-off period is in the range from 540 s to 610 s,while the theoretical period based on cut off period error model is in the range from 530.6 s to 614.9 s.The obtained consistency between calibration and theoretical results justifies the validity of the model developed.The models provide theoretical guidance for controlUng cut off period of sensors and fine batch design.