Is the microphone an input device or an output device?

The microphone is the input device. Input devices are used to input commands, programs, data, text, graphics, images, audio and video information to the computer; microphones are energy conversion devices that convert sound signals into electrical signals, which can input audio information to the computer. So a microphone is an input device.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Input devices and output devices are key devices for human-computer interaction.

The output device (Output Device) is the terminal device of the computer hardware system, used to receive the output display, printing, sound, and control of peripheral device operations of computer data. It also expresses various calculation result data or information in the form of numbers, characters, images, sounds, etc. Common output devices include monitors, printers, plotters, image output systems, voice output systems, magnetic recording devices, etc.

Input device: A device that inputs data and information to the computer. It is used to input commands, programs, data, text, graphics, images, audio and video and other information to the computer. Keyboards, mice, cameras, scanners, light pens, handwriting input tablets, joysticks, voice input devices, etc. are all input devices. The voice input device includes a microphone.

Microphone

The scientific name is microphone, translated from the English microphone (microphone), also known as Microphone, microphone. A microphone is an energy conversion device that converts sound signals into electrical signals. Classifications include moving coil, condenser, electret and recently emerging silicon micromicrophones, in addition to liquid microphones and laser microphones. Most microphones are electret condenser microphones, which work by utilizing a diaphragm of polymeric material that provides permanent charge isolation.

Classification of microphones:

Microphones can be divided into two types: electric microphones and condenser microphones based on their transduction principles. Among them, the electric type can be subdivided into dynamic microphones and aluminum ribbon microphones.

• Common commercial microphone types include condenser microphones, crystal microphones, carbon microphones and dynamic microphones.

• There are two energy sources commonly used in condenser microphones: DC bias power supply and electret film.

Both condenser microphones and crystal microphones convert sound energy into electrical energy, producing a changing electric field. Carbon microphones use a DC voltage source to change their resistance through sound vibrations, thereby converting acoustic signals into electrical signals.

Condenser, crystal and carbon microphones all produce a voltage signal proportional to the displacement of the sensitive membrane, while dynamic microphones produce a voltage signal proportional to the vibration rate of the sensitive membrane.

The dynamic microphone uses permanent magnets as the energy source and converts sound energy into electrical energy based on the inductive effect.

Technical indicators

• Sensitivity

  refers to the ratio of the open circuit voltage of the microphone to the sound pressure acting on its diaphragm . In fact, the microphone will inevitably cause sound field scattering in the sound field, so there are two definitions of sensitivity. One is the sound pressure actually acting on the diaphragm, which is called sound pressure sensitivity. The other refers to the sound field sound pressure when the microphone is not placed in the sound field, which is called sound field sensitivity. The sound field sensitivity is divided into free field sensitivity and diffusion. field sensitivity. Usually recording microphones give sound pressure sensitivity, and measurement microphones give sound pressure or sound field sensitivity depending on the type of application.

  The unit of sensitivity is Volt/Pa (Volt/Pascal, V/Pa), which is usually expressed by sensitivity level. The reference sensitivity is 1V/Pa.

• Frequency response

  means that when the microphone receives sounds of different frequencies, the output signal will amplify or attenuate as the frequency changes. The most ideal frequency response curve is a horizontal line, which means that the output signal can directly present the characteristics of the original sound, but this ideal situation is not easy to achieve. Generally speaking, the frequency response curve of a condenser microphone is flatter than that of a dynamic microphone. Most common microphone frequency response curves are attenuation of high and low frequencies, while mid- and low-frequency frequencies are slightly amplified.

  In the frequency response curve graph, the horizontal axis is frequency, the unit is Hertz, and in most cases it is expressed as a logarithm; the vertical axis is sensitivity, the unit is decibels.

• Impedance

  The 3-pin XLR connector can produce a balanced output signal, which can effectively eliminate external noise interference. The three pins will be marked with three numbers: 1, 2, and 3; in US regulations, 1 represents the ground wire, 2 represents the positive phase (hot) signal, and 3 represents the reverse phase (cold) signal; in European regulations, 1 represents the ground wire , 2 represents the reverse phase (cold) signal, and 3 represents the positive phase (hot) signal.

• The signal-to-noise ratio

  is measured by the logarithm of the ratio of the microphone output signal voltage to the microphone's intrinsic noise voltage. Generally, the S/N value of high-quality condenser microphones is 55~57dB.

• Dynamic range

  Small dynamic range will cause sound distortion and deterioration of sound quality, so a large enough dynamic range is required.

• Equivalent noise level

  The output voltage generated by the sound pressure of the sound wave acting on the microphone is equal to the output voltage generated by the inherent noise of the microphone itself. The sound pressure of the sound wave is equal to the equivalent noise level of the microphone.

• Total Harmonic Distortion (THD)

  Harmonic distortion refers to the harmonic component that the output signal has more than the input signal. Harmonic distortion is caused by systems that are not perfectly linear. The sum of all additional harmonic levels is called total harmonic distortion. Generally speaking, the total harmonic distortion at the frequency of 500Hz is the smallest, so many products use the distortion at this frequency as its indicator. The total harmonic distortion is 1% to F, which cannot be distinguished by the ear. If it exceeds 10%, the distortion components can be clearly heard. The smaller the value, the purer the sound, indicating the higher quality of the product. The total harmonic distortion of general products is less than 1% (measured at 500Hz frequency)

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