EPTFE Acoustic Vent Membrane For External Road Noise Cancellation Microphone

This EPTFE acoustic vent is engineered for external road noise cancellation (RNC) microphones placed in wheel wells, underbody, and near the exhaust system. These reference microphones must capture low-frequency road roar with high fidelity to generate accurate anti-noise signals, yet they face the most aggressive environmental attacks in the vehicle: high-pressure water, slush, de-icing chemicals, and flying gravel. The vent’s tailored acoustic resistance (500 Rayls typical) provides a precise acoustic path that preserves the microphone’s frequency response down to 20 Hz while blocking all liquids. The composite structure, bonding EPTFE to a heavy-duty mesh, resists puncture from pebbles and ice fragments. It endures steam jet cleaning (IP69K) and 1500-hour salt spray testing without any ingress, ensuring the RNC system operates correctly throughout the vehicle’s life. This vent is a key enabler for achieving luxury-level cabin quietness in mass-market vehicles.

RNC systems rely on accurate noise reference signals. If the external microphones become clogged with mud or water-soaked, the noise measurement becomes corrupted, and the cancellation algorithm may actually amplify noise. This EPTFE vent provides a permanently dry, calibrated acoustic path that keeps the microphone operating at its designed sensitivity. The robust physical protection means the mic can be placed closer to the noise source for better coherence, improving cancellation performance. The solution helps OEMs avoid the cost and weight of traditional passive sound deadening, contributing to lighter, more efficient vehicles.

Wheel well RNC reference microphones, underbody noise sensing mics, exhaust system acoustic monitoring, and chassis vibration sensors with acoustic inputs.

Low-frequency road noise travels as pressure waves through the EPTFE membrane to the microphone element. The vent’s calibrated acoustic resistance ensures a predictable, linear transfer function that the ANC system can rely on. Water, mud, and salt solutions are blocked at the surface because the pore size is too small to allow liquid penetration at typical driving pressures. The high water entry pressure ensures that even when submerged in a puddle at speed, water does not force its way through. The tough backing mesh absorbs stone impacts and prevents tearing.