Patent GB-351947-A (GB)
Title: Improvements in auditoriums
IPC: E04B1/99
Filed: 1929-12-28
Abstract: 351,947. Auditoriums; controlling acoustic properties of buildings. COOKE PATENTS, Inc., 26, Liberty Street, New York, U.S.A.-(Assignees of Cooke, H. L. ; Princeton University, New Jersey, U.S.A.) Dec. 28, 1929, No. 39698. Convention date, Dec. 31, 1928. [Classes 20 (i) and 20 (ii).] The curved reflecting surfaces, such as walls and ceilings of theatres, concert halls, and like auditoriums, are so designed in relation to the audience curve or curves that predetermined intensities of sound are produced at any radius from a source point, and those intensities shall be substantially the same for all parts lying equidistantly from the source point. The audience curve may be selected as approximating to a logarithmic spiral A, A<1>, Fig. 5, with the origin at the point 0, the source of the sound, and the seating arrangements are provided on the area formed by swinging this curve horizontally about the vertical axis OZ through O, Fig. 5, or through a point O<1>, Fig. 3, at the rear of O. The ceiling and other reflecting surfaces are so formed according to stated formulµ that the reflections from the several portions thereof serve to re-enforce the direct waves received from the source of sound at the various points of the audience area, either to render the intensity of sound uniform and of equal intensity as that received at a critical point p at a distance r from the source point, or alternatively to cause the intensity of sound to vary as the distance from the source. In order to avoid disturbances by repeated reflections from the back of the auditorium the ceiling or reflecting surfaces are so positioned that the reflected reenforcing waves from those surfaces impinge practically normally on the audience curves and are thus reflected back to the reflecting surfaces and thence to the stage where they are absorbed or dispersed. The auditorium may be arranged as shown in Fig. 3, the plan being in the form of a sector of a circle with the stage attached at O and to avoid diffraction of sound waves the front part of the ceiling or reflecting area N is formed as a spherical surface with centre O, so that the waves impinging thereon are reflected back to the source. Where galleries are provided the shape of the rear part of the ceiling curves is so designed that the reflections from them re-enforce the audience curves in the galleries. Instead of the reflecting surfaces being so designed as to cause uniformity of audibility throughout the audience area they may be so arranged to cause an audibility varying according to some function of the distance from the source of sound so that the intensity of reception may increase or decrease with respect to the intensity at a certain critical distance. The Specification as open to inspection under Sect. 91 (3) (a) comprises also an auditorium in which the rear surface of the stage may be formed as a reflecting surface as at P‹, C‹, Fig. 12 (Cancelled), to re-enforce the sounds in the galleries or again, the sides of the building instead of being flat may be formed with curved hollows G, G<1> by which the sound waves are deflected to the spaces beneath the galleries, Figs. 14 (Cancelled) and 15 (Cancelled). The incident and reflected rays from the reflecting surfaces may not necessarily lie in the same vertical plane to produce the desired results, and Fig. 14 (Cancelled) shows an egg-shaped building designed according to stated formulµ to give the necessary re-enforcement. Where extended wave fronts I such as orchestras are employed, consideration must first be had to the changes of audibility caused by reflections from the side walls, in conjunction with the direct sound waves, and then the reflecting surfaces are so designed to re-enforce the summation effects for different lines of audience disposed parallel to the side walls, Fig. 9 (Cancelled). This subject-matter does not appear in the Specification as accepted.