1. A breathing apparatus speech enhancement system comprising: a breathing mask; a primary sensor on the breathing mask and configured to produce a primary signal; at least one reference sensor on the breathing mask and configured to produce a reference signal; and, a processor which combines at least the primary signal and the reference signal to produce an output signal with an enhanced speech component, wherein the processor is configured to: use a filter to filter the reference signal and subtract the filtered reference signal from the primary signal to produce the output signal; update the filter based on the output signal and the reference signal; and only update the filter when the processor detects the exclusive presence of an alarm signal by: receiving the primary signal; determining the energy of the primary signal; and analyzing the energy of the primary signal to determine whether the alarm signal is exclusively present.