Microphone
Dec 26,2022
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Most microphones are electret condenser microphones (ECM), which have been used for decades. The working principle of ECM is to use a polymer vibrating membrane with permanent charge isolation. Compared with the polymer vibration film of ECM, the performance of MEMS microphone is very stable at different temperatures, and will not be affected by temperature, vibration, humidity and time. Due to its high heat resistance, MEMS microphones can withstand the high temperature reflow soldering at 260 ℃ without any change in performance. Since the sensitivity changes little before and after assembly, this can even save the cost of audio debugging in the manufacturing process. At present, integrated circuit technology is more and more widely used in the manufacture of sensors and sensor interface integrated circuits. This micro manufacturing process has the advantages of precision, flexible design, miniaturization of size, integration with signal processing circuits, low cost and mass production. The early micro microphone was based on piezoresistive effect. According to research reports, it was made with (1 × 1)cm2、2 μ Microphone with m-thick polysilicon film as the sensing film. However, if there is no stress in the sensitive film, the first resonant frequency of such large and thin polysilicon film will be lower than 300Hz. The first-order resonant frequency in such a low frequency range will cause the frequency response of the microphone in the auditory frequency range to be extremely uneven (the change of sensitivity is greater than 40dB), which is unacceptable for microphone applications. When there is tensile stress in the sensing film, its resonant frequency will increase at the expense of sensitivity. Of course, a higher first-order resonant frequency can be obtained by adjusting the size of the sensitive film, but this will still reduce the sensitivity. It can be seen that the piezoresistive scheme is not suitable for the manufacture of micro microphones [3].
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Most microphones are electret condenser microphones (ECM), which have been used for decades.
2022-12-26
The power distribution of the main speaker system for sound reinforcement should be based on the determined number of combinations and the power amplifier without distortion power conditions, and the appropriate number should be selected. For the speaker drive, the pre-frequency division method can be used, or the power frequency division method can be used. In order to ensure the rationality and reliability of the sound box system in the hall, special treatment must be made in the grouping and wiring technology of power distribution.
2017-11-15
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