Claire always used a windscreen on her measurement microphone. Outdoors, indoors, in a sealed chamber — the windscreen was always on. 'Protection,' she said. 'You never know when someone might sneeze near the mic.' This was technically true but acoustically expensive.

A foam windscreen attenuates high frequencies. At 1 kHz, the effect is negligible — maybe 0.2 dB. At 4 kHz, it's about 0.5 dB. By 10 kHz, a typical foam windscreen introduces 1-2 dB of attenuation. At 16 kHz, it can reach 3 dB or more. These are small numbers that add up to a systematic high-frequency measurement error.

Claire had been submitting measurement reports for two years that showed every room she measured had slightly reduced high-frequency reverberation compared to predictions. Her RT60 values above 8 kHz were consistently 0.1-0.2 seconds lower than calculation models predicted. She chalked this up to 'real-world conditions always differing from models,' which is true but wasn't the explanation here.

The windscreen was absorbing enough high-frequency energy at the microphone capsule to reduce the measured reverberant level, which made the RT60 calculation produce artificially low values. Every room she measured appeared to have slightly better high-frequency absorption than it actually had. She had been under-specifying HF treatment for two years based on this phantom absorption.

The Moral: Every element in the measurement chain affects the result. SonaVyx's mic calibration system lets you apply frequency-dependent corrections — including windscreen compensation — so your measurements reflect the room, not your accessories.