Complex sentence: Non Verbal Auditory Agnosia is the inability to comprehend environmental (nonverbal) sounds which appear unintelligible, e.g. an airplane roaring overhead would not be understood to be related to the idea of "airplane"--indeed, the person would not even think to look up.
Split into simpler sentences: Non Verbal Auditory Agnosia is the inability to comprehend environmental (nonverbal) sounds which appear unintelligible. They are unable to say exactly what the sound is, e.g. (6) an airplane roaring overhead would not be understood to be related to the idea of "airplane"--indeed, the person would not even think to look up.