Scientists Built Earmuffs That Control Why Your Voice Sounds Weird

Researchers at RWTH Aachen University built a device to control the occlusion effect for own voice perception studies. The occlusion effect is the change in eardrum sound pressure caused by occluding the ear canal, and it consists of two phenomena: an insertion loss that attenuates air-conducted sounds, and an occlusion gain that amplifies bone-conduction. Because the effect varies widely between individuals, producing repeatable, precise occlusion conditions for perceptual experiments is difficult, and the system must control the insertion loss and occlusion gain separately. Their approach modifies commercial earmuffs with integrated microphones, along with dedicated impedance measurements and digital filters applied to the microphone signals to emulate arbitrary occlusion effect curves. Objective measurements showed the headphones' inherent occlusion gain stays below 6 dB above 115 Hz and below 0 dB above 155 Hz, and emulation worked accurately across the entire frequency range of interest. Limitations are a slight residual inherent occlusion gain for deep voices and the system's processing delay. Future work will focus on perceptual evaluation of the system and its application in perceptual studies.