Which EMC (electromagnetic compatibility) devices are helpful for hearing aid design and modification?

Hearing aid EMC design is a balance between miniaturization and high performance. The entire circuit must utilize a multi-layer PCB, providing complete ground and power planes. Microphone preamplifiers and receiver (speaker) driver circuitry require careful layout, kept away from digital and wireless components. Decoupling capacitors in 0402 or 0201 packages are widely used on power pins. Radio frequency interference (RFI) suppression relies primarily on PCB grounding design and, possibly, miniaturized filter components (e.g., miniature beads, LC filters). For Bluetooth hearing aids, antenna design needs optimization, and a balanced-to-unbalanced converter (balun) may be used to improve matching and suppress common-mode radiation.