碳粒式麦克风，有时称作纽扣式麦克风或碳粒式传声器，是一种能将声音转化为电子信号的传感器，由两片分开的金属薄片及其之间的碳粒组成。朝外的那块金属薄片作为传导震动片。当声音使薄片振动时，会使其改变对碳粒的压力，会进一步改变两薄片之间的电压 (挤压碳粒使其更加紧密，因此压力越大薄片间电压越小)。当在两金属薄片之间施加直流电压，变化的电压会带来电流的变化，这些变化可以通过电话系统传输，或在电子系统中将声音转化成电信号。

在19世纪20年代，真空管电子放大器开始广泛应用之前，碳粒式麦克风是获得高品质音频信号的唯一实际的方法，被广泛用于电话系统中。它的制造成本低，输出信号强，以及良好的高频输出特性使其非常适用于电话系统，直到19世纪80年代，新安装的电话仍然在使用碳粒式麦克风。在此之前，它们在其他应用领域早已被其他类型的麦克风取代（在绝大多数的西方铜线电话网络中，旧式基于碳粒式麦克风的电话仍在使用未被淘汰）。 碳粒式麦克风曾被广泛应用于早期的调幅无线广播系统中(一般为改进过的电话麦克风)，但由于它们有限的响应频率，以及有较高的噪音，遂于19世纪20年代在该领域中被淘汰。接下来的数十年，它们继续被广泛应用于低端播音、军事以及业余无线电应用。

The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony, this undulating current is directly passed through the telephone wires to the central office. In public address systems or recording devices it is amplified by an audio amplifier. The frequency response of the carbon microphone, however, is limited to a narrow range, and the device produces significant electrical noise.