Method for detecting a direction of arrival of an acoustic target signal and binaural hearing system

A method for detecting a direction of arrival of an acoustic target signal by use of a plurality of microphones, the microphones being distributed over a first hearing instrument of a binaural hearing system as a local device and a second hearing instrument of the binaural hearing system as a remote device, the local device containing at least a first local microphone and a second local microphone, and the remote device containing at least a first remote microphone, each of the microphones configured to generate a corresponding microphone signal from an environment sound, respectively, the method comprises the steps of:

• deriving a first local input signal by means of a first local microphone signal and a second local microphone signal;
• deriving a second local input signal by means of the first local microphone signal and/or the second local microphone signal;
• deriving a first remote input signal by means of at least a first remote microphone signal, the first local input signal, the second local input signal and the first remote input signal forming a part of a set of input signals;
• deriving a plurality of spatial feature quantities, the spatial feature quantities each being derived from different respective pairs out of the set of input signals, and being indicative of a spatial relation between two corresponding ones of the input signals, deriving each of the spatial feature quantities from a respective pair out of the set of input signals by a same mathematical relation and/or algorithm, varying the respective pairs of input signals for different said spatial feature quantities;
• using the spatial feature quantities as an input to a neural network;
• estimating, by means of the neural network, the direction of arrival of the acoustic target signal;
• and
• wherein as the spatial feature quantities, corresponding intra-microphone responses between the respective two input signals out of the set of input signals are derived, each of the intra-microphone responses being a ratio of cross power spectral densities of an underlying pair of the input signals and of an auto power spectral density of one out of the pair of input signals, or a ratio of cross-correlations of the underlying pair of input signals and of an auto correlation of one out of the pair of input signals.