An evaluation on voice intelligibility for factory noise reduction based on integration of active noise control and auditory masking

Factory noise has been focused upon as one of the social problems. Factory workers exposed to loud, continual noises feel strong discomfort by hearing the loud factory noises for a long time. We have previously proposed an integration method of the active noise control (ANC) and the auditory masking for a noise reduction. The ANC reduces the sound pressure level of the noise in a lower-frequency band by emitting the secondary signals, and the auditory masking reduces discomfort which caused the spectral peaks in a higher-frequency band by emitting the secondary signals. We confirmed that the proposed method is effective for reducing discomfort. However, the method might disturb conversations among the workers by emitting secondary signals. In this study, we therefore evaluated the voice intelligibility of the noise-reduced speech obtained by applying the proposed method to the noisy speech recorded in the factory. As a result of the evaluation experiment, we confirmed that the proposed method can keep voice intelligibility almost the same as the intelligibility of the clean speech in the amid factory noise. In addition, we investigated the relationship between the voice intelligibility and each method under the condition that the controlling frequency-bands are set at to 0–500 Hz for ANC and 500–5500 Hz for auditory masking.