Audio alarm signals should not conflict with other auditory codes or signals.
Additional Information:
If continuous, relatively loud signals are used, they may render other codes and signals less audible. Thus, it may be necessary to consider the audibility of a signal not just in the presence of ambient control room noise, but also in combination with other signals that might plausibly occur at the same time. To avoid mutual masking, the frequencies of tonal signals associated with alarms that may be active at the same time should be separated by at least 20 percent of the center frequency. Interference among alarm signals is less of a concern if the signals consist of a number of widely separated frequency components or of brief groups of pulses presented at intervals. Techniques are available that allow the audibility of signals in noise to be predicted.