elektreettimikrofonikapselit

Electret microphone capsules, known in Finnish as elektreettimikrofonikapselit, are compact sound‑transducing devices that convert acoustic pressure waves into electrical signals. The core of a capsule consists of a piezoelectric polymer film that has been permanently charged—an “electret”—to act as a micromembrane. Sound waves flex this membrane, creating a varying capacitance that is translated into a voltage by an integrated field‑effect transistor or a passive circuit.

These capsules are among the smallest and most popular microphones for consumer electronics, including smartphones, digital cameras, headsets, and voice‑activated assistants. Their low power consumption, high sensitivity, and mechanical robustness make them suitable for embedded applications where space and cost constraints dominate. Variations of the basic electret design include condenser‑type capsules with different diaphragm materials (polypropylene, polyester, and metal‑coated films) and modeling of the surround and dome shapes to tailor frequency response and sensitivity. Some advanced capsules feature temperature compensation or laser‑etched diaphragms to improve low‑frequency performance and reduce distortion.

Manufacturing electret capsules typically involves lamination of polymer films, corona discharge or heated ion deposition to impart static charge, and precise machining of the diaphragm and backplate. Quality control monitors the residual charge, diaphragm tension, and electrical impedance to ensure consistent acoustic response. Although newer electromechanical microphones such as MEMS sensors are emerging, electret capsules remain the workhorse in many portable audio devices due to their proven performance and manufacturability.