Everything is changing quietly without knowing it. Even small components as humble as wired microphones are quietly evolving. Microphone, scientific name is microphone, translated from Microphone. A microphone is an energy conversion device that converts sound signals into electrical signals, also known as a wired microphone.

The history of wired microphones dates back to the late 1800s, when scientists such as Alexander Graham Bell worked to find better ways to pick up sound, which could be used to improve upon a then-new invention, the telephone. During this time, they invented liquid microphones and carbon particle microphones, which were not ideal, but barely usable.

In the 20th century, wired microphones were originally developed through the conversion of acoustic and electrical resistance into inductance and capacitance. A large number of new microphone technologies have been gradually developed, including aluminum ribbon, dynamic coil and other microphones, as well as the widely used condenser microphones and electrets.

Microphones currently on the market mainly include dynamic, condenser, electret and emerging silicon microwired microphones, as well as liquid wired microphones and laser wired microphones. Dynamic mics have better sound quality, but are bulky. Wired microphones are small in size and low in cost, and are widely used in devices such as telephones and mobile phones.

Microphones used as input for audio signals have always suffered from noise problems.

Noise sources in wired microphones come from multiple sources: electronic noise caused by bias voltage fluctuations, FET noise, board-level noise, acoustic self-noise from the diaphragm, and external electromagnetic (EM) fields and radio frequencies coupled into the microphone's high-impedance input . FET (RF) field. Details are as follows:

(1) When a system with ECM (Electret Condenser Microphone, electret condenser microphone) is close to a radio frequency transmission with power control (such as a mobile phone), the audio component of the radio frequency signal generated by power control can be demodulated by the microphone, and converted into an audible sound signal in the audio path.

(2) In the ECM signal amplifying circuit, the threshold of the transmitting power amplifier (appearing in the audio frequency band) is adjusted by the high impedance threshold of the FET to amplify the signal. Once this signal enters the audio frequency band, it is very difficult to eliminate.

(3) Power supply voltage fluctuations are also a very common source of noise in audio systems. As a low sensitivity ECM, its output is a small analog signal on the order of 10mVrms. Since the ECM does not have any power supply rejection, small fluctuations in the power supply voltage cause intermittent noise.

(4) ECM also poses mechanical design challenges. Because the ECM can detect not only sound signals but also mechanical vibrations and convert the vibrations into low frequency sound signals, when the ECM is placed in a vibrating environment (such as mounted on a circuit board near an electric fan or a large speaker), the vibration will be The main source of noise in an audio system.