Abstract: An active noise-reduction headphone arrangement has a housing bearing a loudspeaker having a first diaphragm surface coupled to a first volume of air bounded by and coupled to a user's ear, and a second diaphragm surface bounding a cavity within the housing assembly so as to define a second volume of air, rearward of the diaphragm; a conduit provided in the housing, the conduit being in fluid communication the ambient air via a first acoustic couple means having a first characteristic acoustic impedance, the conduit also being in fluid communication with said second volume of air via a second acoustic couple means having a second characteristic acoustic impedance; and a microphone having an inlet coupled acoustically to a predetermined location within the conduit.

Abstract: A MEMS microphone assembly has an enclosure enclosing a volume of air. A MEMS microphone chip is provided within the enclosure. First and second acoustic ports are formed in the enclosure, defining first and second fluid paths between the volume of air and air outside the enclosure. The MEMS microphone responds to a pre-determined linear interpolative value between two independent pressure signals supplied via first and second ports according to the potentiometic ratio of the acoustic impedances of the first and second ports.

Abstract: This invention relates to a device for and method of implementing an ambient noise-cancellation (ANC) circuit that uses digital processing whereby a signal indicative of the ambient noise is converted to digital form, filtered, using a fixed or adaptive digital filter, and then converted back to analogue before sending it to an ear-proximate speaker. In order to address the time delays associated with such processing operations, the analogue-to-digital converter used is associated with a down-sampler, and the arrangement is such that a first part of the filtering is implemented by the down-sampler, and a second part of the filtering is implemented by the digital filter. This reduces group delay by configuring a down-sampler associated with the front end of the analogue-to-digital converter to incorporate selected filter characteristics of the overall ANC filter response, and modifying the subsequent filtering processing stage to compensate for this.

Abstract: The invention is intended to facilitate the production of ambient noise- cancelling earphones and, to that end, provides a module (30) comprising a microspeaker (34) and an electret microphone (38) both carried on a common substrate (32) which is also configured to incorporate an acoustic resistor (33, 35). The module (30) is incorporated into an earpiece having electrical connections to noise-cancelling electronic circuitry that is provided separately from the earpiece and is housed, for example, in a separate pod (82, 102) or incorporated within the body of a cellular telephone. The performances of the microspeaker (34) and microphone (38) are classified against one or more predetermined operational criteria, enabling the noise-cancelling circuitry to be configured to allow for departures from such criteria.