The book is indeed a great one, "Motion Picture Sound Engineering," published by the Research Council of the Academy of Motion Picture Arts and Sciences, Van Nostrand 1938. L.E. Clark and John K. Hilliard wrote Chapter VII, "Headphones and Loud-speakers." Hilliard's excellent writing is basically a summary of the results of the Shearer Horn Project conducted at MGM Studios. Essential reading IMO.

The seller evidently hid the title so that buyers wouldn't look elsewhere for a cheaper copy. Who in the world would do such a thing?

motion picture sound engineering - AbeBooks