Interpretation and measurement of acoustic phase response

This note is inspired to an article published some years ago on Fedeltà del Suono [1]. The motivation to write something about acoustic phase and its implications on listening was originated from the reading of an interesting “Application Note” from Brüel & Kjær [2]: a perfect example of how it is possible to treat in an exemplary, clear way, a not so very intuitive subject like this one. Many technicians and amateurs in this field read and studied this type of publications, and often have taken them as a starting point to improve their research or divulgation activity. It is therefore puzzling that this work, which was presented on occasion of the 48th AES Convention held in California in 1974, could remain largely ignored for a long time. One of the dark sides of high fidelity is that some of its important technical aspects are present and well known in the relevant literature and nevertheless are systematically ignored by designers and sound enthusiasts.