A gas-buffered brush seal assembly and associated method are provided. The input voltage-switching control oscillator includes: an oscillation closed loop that is provided with a variable-voltage capacitance element; and a switch for interchangeably selecting one of a plurality of voltages in accordance with a selection signal and applying the selected voltage as a control voltage to the variable-voltage capacitance element. In one variant, the apparatus includes a receiver connected to the signal processing electronics, and a fastener as a unitary connector of the cover and microphone housing to the housing.