HD Electret Condenser Microphones PUI Audio HD Electret Condenser Microphones are designed for high sensitivity and superior signal-to-noise ratio using premium-grade FETs and diaphragms. PUI HD microphones feature GSM buzz-blocking capacitors. These condenser microphones diameter is designed for extreme fidelity from 20Hz to 20kHz. The HD electret microphones are ideal for medical, automotive, industrial, and consumer products.