Microphones

Crystal Microphone

晶体麦克风

Crystals which demonstrate the piezoelectric effect produce voltages when they are deformed. The crystal microphone uses a thin strip of piezoelectric material attached to a diaphragm. The two sides of the crystal acquire opposite charges when the crystal is deflected by the diaphragm. The charges are proportional to the amount of deformation and disappear when the stress on the crystal disappears. Early crystal microphones used Rochelle salt because of its high output, but it was sensitive to moisture and somewhat fragile. Later microphones used ceramic materials such as barium titanate and lead zirconate. The electric output of crystal microphones is comparatively large, but the frequency response is not comparable to a good dynamic microphone, so they are not serious contenders for the music market.

能够表现出压电效应的晶体在受到形变时会产生电压。晶体麦克风使用一块压电材料薄片固定在振膜上。当晶体被振膜推拉时，晶体的两侧会获得相反的电荷。这些电荷的大小与形变的程度成正比，当作用在晶体上的应力消失时，电荷也会消失。早期的晶体麦克风使用 Rochelle 盐，因为其输出较高，但其对湿度敏感且较为脆弱。后来的麦克风则使用如钡钛酸盐和铅锆酸盐等陶瓷材料。晶体麦克风的电信号输出相对较大，但其频率响应无法与优质动态麦克风相比，因此在音乐市场中并不占优势。

Directional Patterns of Microphones

麦克风的定向模式

Characteristic 特征	Omnidirectional 全向的	Cardioid 心形线	Supercardioid 超 cardioid	Hypercardioid 超心形	Bidirectional 双向的
Pickup arc 3 dB down 拾取弧3 dB下降	...	131°	115°	105°	90°
Pickup arc 6 dB down 拾取弧6 dB下降	...	180°	156°	141°	120°
Relative output at 90° in dB 90°时的相对输出（dB）	0	-6	-8.5	-12	-inf -∞
Relative output at 180° in dB 180°时的相对输出（dB）	0	-inf -∞	-12	-6	0
Angle at which output = 0 输出等于0时的角度	...	180°	127°	110°	90°

The variety of directional patterns are often characterized by the arc within which they pick up at least half the peak value. In decibels, a drop of 3 dB represents half the power and 6 dB down is one fourth the power.

各种方向图通常通过其能拾取至少峰值一半的弧来表征。以分贝计，3 dB的下降表示功率的一半，6 dB的下降则表示功率的四分之一。

With any of the microphone mechanisms, different directional patterns of response can be produced. Common directional patterns are called cardiod (for heart shaped) and omnidirectional. There are also "figure-eight" patterns which accept sound from front and rear. The parabolic microphone is unidirectional in the extreme!

无论使用哪种麦克风机制，都可以产生不同的指向性模式。常见的指向性模式称为心形（因形似心脏而得名）和全向性。还有“双耳形”模式，可从前方和后方接收声音。抛物面麦克风在极端情况下是单向的！

One directional technique used is the "stereo microphone" which may be constructed from two condenser microphones attached to each other so that their peak response directions are 90° apart. Although stereo effects may be obtained with two separate microphones, the stereo pair offers a way to get some stereo effect with a single microphone placement.

一种方向性技术是使用“立体声麦克风”，它可能由两个电容式麦克风连接而成，使得它们的峰值响应方向相互垂直。虽然使用两个独立麦克风也可以获得立体声效果，但立体声配对提供了一种通过单个麦克风位置获得某些立体声效果的方法。

Parabolic Microphone

抛物面麦克风

For recording distant bird or animal sounds, or for just plain eavesdropping, it is hard to beat the directionality and sensitivity of the parabolic microphone.

对于录制远处的鸟或动物声音，或者仅仅是窃听，很难超越抛物面麦克风的方向性和灵敏度。