A method of manufacturing an Active Noise Reduction, ANR, device (1"), comprising: providing at a stage during manufacture a pre-completion ANR device in a non-final configuration, the pre-completion ANR device comprising: a plurality of inputs (10, 11)(2"); a plurality of signal processing resources (14,15)(5") comprising: a plurality of analogue signal processing resources; and a plurality of digital signal processing resources; an output (3 ") for driving an earphone driver; and a programmable switch arrangement (12, 13)(4") capable of assigning any of the plurality of inputs (10, 11)(2") to any of the plurality of signal processing resources (14, 15)(5"); selecting from the plurality of signal processing resources (14, 15)(5") a subset of signal processing resources to contribute to the output (3"), whereby the remaining signal processing resources of the plurality are unselected; and in a configuration step during manufacture, programming the programmable switch arrangement (12, 13)(4") to assign each of at least a subset of the plurality of inputs (10, 11)(2") to a different one of the selected subset of signal processing resources to enable the selected subset of signal processing resources to contribute to the output (3"), whereby the unselected signal processing resources of the plurality of signal processing resources (14, 15)(5") are configured not to contribute to the output (3 ") in any mode of operation of the ANR device (1"). providing at a stage during manufacture a pre-completion ANR device in a non-final configuration, the pre-completion ANR device comprising: a plurality of inputs (10, 11)(2"); a plurality of signal processing resources (14,15)(5") comprising: a plurality of analogue signal processing resources; and a plurality of digital signal processing resources; an output (3 ") for driving an earphone driver; and a programmable switch arrangement (12, 13)(4") capable of assigning any of the plurality of inputs (10, 11)(2") to any of the plurality of signal processing resources (14, 15)(5"); a plurality of inputs (10, 11)(2"); a plurality of signal processing resources (14,15)(5") comprising: a plurality of analogue signal processing resources; and a plurality of digital signal processing resources; a plurality of analogue signal processing resources; and a plurality of digital signal processing resources; an output (3 ") for driving an earphone driver; and a programmable switch arrangement (12, 13)(4") capable of assigning any of the plurality of inputs (10, 11)(2") to any of the plurality of signal processing resources (14, 15)(5"); selecting from the plurality of signal processing resources (14, 15)(5") a subset of signal processing resources to contribute to the output (3"), whereby the remaining signal processing resources of the plurality are unselected; and in a configuration step during manufacture, programming the programmable switch arrangement (12, 13)(4") to assign each of at least a subset of the plurality of inputs (10, 11)(2") to a different one of the selected subset of signal processing resources to enable the selected subset of signal processing resources to contribute to the output (3"), whereby the unselected signal processing resources of the plurality of signal processing resources (14, 15)(5") are configured not to contribute to the output (3 ") in any mode of operation of the ANR device (1").