Directional microphone processing effectively reduces the cognitive load of listening to speech in background noise. This is significant because it is likely that listeners with hearing impairment will frequently encounter noisy speech in their everyday communications.
There are a number of directional microphone systems and these may be engaged manually (program button or remote control) or automatically based on signal processing decisions designed for given listening environments (for example speech in noise or speech in quiet).
Fixed directional uses one of the polar patterns; automatic fixed directional can access the same cardioid patterns as fixed but usually engage automatically in the presence of background noise. Automatic adaptive systems can switch the directional microphones on or off and also change polar patterns according to the relationship between the listener and a noise source.
Adaptive directionality is usually a feature in the ‘high end’ product range and allows either a manual or automatic selection of available polar plots, thus maximising potential signal to noise ratios.