oldhvy - Wan't "big hears" the system they use in Hawaii before WWII? It was suppose to "listen" for incoming aircraft before they actually had radar. From the story I remember, they thought the sound it picked up was US aircraft being ferried to Hawaii from the mainland. Turned out to be the zeros attacking.
Correct ear alignment
I have found that the string loops on face masks put my ears in perfect alignment for critical listening.At our local Audiophile Salon it has become a mandatory “ thing” at our Saturday morning ears and coffee get together. It even improves the sound of my Bose system in my Ferrari 599 GTB.