Microphone capsules are typically connected to the input of an amplifier, placing them in a sensitive area that is vulnerable to electromagnetic interference (EMI) from the environment, which can create unwanted noise.
The microphone capsule itself is shielded with a metal casing, making it difficult for external electromagnetic interference to penetrate. However, EMI typically enters the circuit through the microphone capsule's leads, causing interference.
Unfortunately, some product engineers neglect the importance of selecting the right signal wire for the microphone capsule, often using ordinary wires that can easily introduce interference.
To reduce noise and interference in the final product, it is crucial to use shielded leads, such as twisted pairs or shielded wires.
1. Twisted Pair Wire
Twisted pair wiring consists of two wires of the same specification twisted together into a helix. This type of wire is effective in environments with general electronic interference, providing decent resistance to high-frequency interference.
Why does twisted pair wire resist interference?
When external electromagnetic interference hits the wire, it generates magnetic fields of opposite phases on the positive and negative wires. The twisting of the wires naturally causes the opposing fields to cancel each other out, providing interference resistance.
The tighter the twist of the wires, the better the anti-interference performance.
2. Shielded Wire
In environments with stronger interference or lower-frequency disturbances, twisted pair wires may not be sufficient. In these cases, shielded wire is much more effective.
Shielded wire has an additional metal sheath surrounding the signal wires, typically grounded or connected to the negative terminal.
Low-frequency interference, such as the 50Hz electromagnetic field from AC power lines, is blocked or absorbed by the metal shield surrounding the wire. Since the shield is grounded, the interference is diverted to the ground (zero potential), effectively filtering out the noise.
Shielded wires come in various grades. Low-quality shielded wires may have a sparse copper wire shielding, while higher-quality wires feature denser copper shielding wrapped around the signal wires. Premium shielded wires often use a mesh layer to tightly encase the signal wires, providing the best performance-though at a higher price.
