The sound track book of the theatre (undated)

ACOUSTICAL PROBLEMS 297 space through the screen. Installation of Acoustical Material To obtain as nearly as possible a straight line absorption across all frequencies, the acoustical material is applied on furring strips. The diaphragmatic action of such mounting on furring strips goes far in absorbing those low tones between 60 and 300 cycles that are largely responsible for a "boomy" house. It was their original efforts to eliminate this booming which convinced engineers that the most satisfactory reverberation time for the majority of houses is one slightly on the dead side as compared with optimum times for general use auditoriums. This does not mean that any tendency toward "deadness" is sought, but rather that a little less reverberation is allowed than for an auditorium in which the sound of the performance is not electrically amplified. Projection Room There are two important reasons for acoustical treatment of the projection room. First, theri is the machine noise that escapes into the audience area through the ports. This is particularly objectionable where the projection room opens immediately into the balcony. Even more important than reduction of the noise escaping into the auditorium are improved hearing conditions within the projection room, where the monitor horn is located. No projectionist can be expected to handle properly the sound in the auditorium when the reproduction from his monitor horn is masked by machine noise. Substantial reduction of this noise can be effected by treating the ceiling of the projection room with an incombustible acoustical material. Other Theatre Areas Sound conditioning to suppress noise in foyers, lounges, and around refreshment booths is a problem that also needs attention in many theatres; however, since this is apart from acoustical correction in the auditorium, it will not be discussed here. fSo you're building nothing but open air theatres?" "Sure, no overhead."