在电容传声器,包括驻极体传声器中,由于传声器头的内阻抗非常高,一般都紧接传声器头加装一前置放大器,用以变换阻抗。然而,前置放大器输出的固有电噪声又限制着传声器的动态范围向低端发展,即传声器所能接受声信号的最低声压级受到传声器等效噪声级的限制。因此,测量和降低前置放大器以至整个传声器的固有电噪声,已经成为保证和提高传声器性能的一个重要问题。根据定义,在测量固有电噪声时,必须加上 A 计权,以模拟人耳的听 In condenser microphones, including electret microphones, since the internal impedance of the microphone head is very high, a preamplifier is usually installed immediately next to the microphone head to change the impedance. However, the inherent electrical noise output from the preamplifier limits the dynamic range of the microphone to the low end. That is, the minimum sound pressure level at which the microphone can receive acoustic signals is limited by the microphone’s equivalent noise level. Therefore, measuring and reducing the inherent electrical noise of the preamplifier to the entire microphone has become an important issue for ensuring and improving microphone performance. By definition, A-weights must be added to measure the inherent electrical noise to simulate the listening of the human ear