Effect of active noise control and masking sound on speech intelligibility

Passengers sitting in the back seats of cars while talking on their phones can easily have the privacy of their speech invaded by the driver. One way of protecting speech privacy is to utilize masking sounds, which may also lower speech intelligibility- masking sound may be so loud that it annoys both drivers and speakers. Here, we evaluate the feasibility of utilizing active noise control (ANC), which aims to reduce the level of speech targeted toward the driver, thus lowering the needed level of masking sounds while still protecting speech privacy. Evaluation of speech intelligibility has been completed both objectively and subjectively using Speech Intelligibility Index (SII) and Speech Reception Threshold (SRT), respectively. SII value calculation has shown that ANC is not effective at lowering the level of masking sounds and speech intelligibility. On the other hand, SRT measurement has shown that ANC, which reduces the speech level to around 10 dB below 1000 Hz, is able to lower the level of masking sounds by about 5 dB.