Development of an Active Noise Cancellation Hearing Protector: How Can Passive Attenuation Be Retained?

Abstract

The modest low-frequency attenuation of the conventional passive hearing protector can be improved electronically by active noise cancellation techniques. This paper presents the theory and some of the actual limitations of an active noise cancellation hearing protector. Three prototypes with similar types of controller, but with different mechanical construction were made and their performance was measured. The electronics of the system were implemented using analog electronics and feedback construction. The measurement results were compared with the results of an equivalent passive hearing protector with no internal electronics and with an intact earcup. The results show that the integration of the controller inside the earcups degrades the passive attenuation of the hearing protector at frequencies below 200 Hz. With proper design, an active noise cancellation hearing protector can still have 15 dB more noise attenuation at 100 - 200 Hz range than an equivalent passive hearing protector.

Active Noise Reduction Algorithm Based on NOTCH Filter and Genetic Algorithm

“…Sounds of higher frequencies carrying the main information message of the speech signal are attenuated very well, while lowfrequency sounds which are the masking signal for the speech signal are poorly attenuated. These problems can be solved by application of active noise reduction systems which allow for a more effective reduction of low-frequency noise (Oinonen et al, 2006). The use of lighter hearing protectors with poorer attenuation in the high-frequency band additionally provided with active noise reduction systems increasing their attenuation in the higher-frequency band often results in improved intelligibility of speech of individuals using hearing protectors (Prashanth, 2010;Pawełczyk, Latoś, 2010).…”

Performance Analysis of an Active Noise Cancellation Hearing Protector

“…There is a trade-off between active and passive performance, which is caused by two factors [6]. First, passive noise attenuation depends on the free volume inside the earcups.…”

“…NOISE & VIBRATION WORLDWIDE equivalent passive hearing protector. Because the integration of the ANC system inside the earcup causes a loss of passive attenuation [6], similar measurements were carried out with an equivalent intact passive hearing protector. Measured at 125 Hz, the sound pressure level inside the earcup is on average 2 dB lower with the passive equivalent than with the ANC hearing protector in passive mode.…”