초록 ▼

The invention relates to a method and to apparatus for attenuating externally originating noise reaching the eardrum while still enabling communication via an electro-acoustic path. Apparatus according to the invention comprises passive attenuation means disposed about each ear and delimiting a cavi

The invention relates to a method and to apparatus for attenuating externally originating noise reaching the eardrum while still enabling communication via an electro-acoustic path. Apparatus according to the invention comprises passive attenuation means disposed about each ear and delimiting a cavity (10). In addition it includes active attenuation means comprising a loudspeaker (6) placed inside the cavity (10) and a microphone (8) placed in the external ear duct or at the inlet thereto, said loudspeaker and microphone being interconnected by a constant gain amplifier (11) and an active analog filter (12) of the polynomial type, with the passive components thereof being designed to provide a given transfer function. One application lies in the construction of protective headsets fitted with incorporated loudspeakers enabling electro-acoustic communication.

대표청구항 ▼

Apparatus for attenuating externally originating noise reaching the eardrum, the apparatus being of the type including passive soundproofing means which together with each ear delimits a respective cavity, and also including an electro-acoustic transducer and a microphone disposed inside each said c

Apparatus for attenuating externally originating noise reaching the eardrum, the apparatus being of the type including passive soundproofing means which together with each ear delimits a respective cavity, and also including an electro-acoustic transducer and a microphone disposed inside each said cavity and interconnected via a feedback loop including a constant gain amplifier and a filter with which they constitute an active sound attenuator, the apparatus being characterized in that the transfer function C(w) of said filter is a complex polynomial function and in that the product of the constant gain K of said amplifier multiplied by the modulus │C(w)│of the transfer function of said filter and by the modulus │H(w)│of the open loop transfer function as measured at the input to said transducer and at the output from said microphone is considerably greater than unity throughout the range of low audio frequencies which are to be attenuated and satisfies the stability criterion for all audible frequencies.