Headphone speech listening

A digital audio processor for use in a headphone, the digital audio processor comprising:

• a transparency digital filter path through which one or more of a plurality of external microphone signals of a primary headphone is to be filtered before driving a speaker of the primary headphone;
• a personalized enhancement digital filter path, which has a higher latency than the transparency digital filter path, through which one or more of the plurality of external microphone signals is to be filtered before driving the speaker of the primary headphone,
• wherein the processor has i) a first transparency mode of operation in which the transparency digital filter path is active while the personalized enhancement digital filter path is inactive, and ii) a second transparency mode of operation in which the transparency digital filter path is inactive while the personalized enhancement digital filter path is active, and in both the first transparency mode of operation and the second transparency mode of operation the speaker reproduces a first sound source and a second sound source that are in ambient environment of the headphone;
• and
• a separator that is to process the plurality of external microphone signals to produce, in parallel, i) a plurality of instances of a first frequency domain filter that represents the first sound source, and ii) a plurality of instances of a second frequency domain filter that represents the second sound source, the separator is to configure digital filter coefficients of the personalized enhancement digital filter path using the first frequency domain filter and the second frequency domain filter with a latency that is longer than that of the transparency digital filter path.