Electret microphones are a type of condenser microphone known for their compact size, simplicity, affordability, and excellent acoustic performance. They are widely used in DSLR interview microphones, DSLR stereo microphones, professional interview microphones, wireless lavalier microphones, and headset microphones, among other professional and consumer applications.
Directional vs. Non-Directional Microphones
Directional properties are a crucial aspect of microphone design. Common directional types include omnidirectional (non-directional), cardioid, and supercardioid. In this article, we will compare the internal structures of two 9.7mm electret microphone elements: one omnidirectional (non-directional) and one supercardioid (directional).
Omnidirectional microphones pick up sound uniformly from all directions, meaning that the volume of the sound remains consistent regardless of the source’s direction. This results in no distinction between ambient noise and the targeted sound source. In contrast, supercardioid microphones are most sensitive to sound coming directly from the front, while sounds from other directions are attenuated. This allows the microphone to clearly distinguish the sound from the target source against the background noise.
Structural Differences
Externally, the omnidirectional microphone’s backplate lacks any holes, meaning sound can only enter through the front, impacting only the front side of the diaphragm with sound pressure. The supercardioid microphone, however, has small holes in the backplate, allowing sound to enter from both the front and these rear holes. This design allows sound pressure to affect both sides of the diaphragm. When the sound does not come directly from the front or rear entry points, the sound pressure on both sides of the diaphragm tends to cancel each other out, reducing the volume. This is the secret behind the directionality of supercardioid microphones.
Disassembly and Comparison
Now, let’s take apart these two electret microphones to compare the internal structures of the omnidirectional and supercardioid models. It becomes evident that, while they operate on similar principles, there are significant differences in their structural design and manufacturing processes, which are key to achieving their respective directional characteristics.
