ACOUSTICS.

Star (Christchurch), Volume LXVI, Issue 20541, 16 February 1935, Page 21 (Supplement)

ACOUSTICS.

Sea Shells an Early Idea. LONDON DISCOVERY. Chesterfield House —once the home of Princess Mary—was recently demolished, a curious discovery was made. Packed tightly between the joists of the floor-beams above the ballroom and filling the entire space between floor and ceiling over the whole area of the room, was a great quantity of sea shells. It appears that the first Earl of Chesterfield had these inserted to improve the acoustics for musical purposes when he took possession of the mansion about 185 years ago, says the London “ Daily Mail.” There is much debate as to what form of building tends to the most perfect acoustics, and from a study of many of London’s concert halls and public buildings eminent architects have evolved the following definite facts:— Square halls produce less satisfactory acoustics than oblong or fan-shaped ones, and domed ceilings than flat ones. Flat ceilings have the effect of distributing the sound more uniformly over the hall below. Fan-shaped halls cause the side walls to act as sound reflectors. Tone quality is improved by resonant wood panelling, and still more so if such panelling is polished. The floor of an orchestra, if polished, strengthens the tones of the instruments. Upholstered seats aid the acoustics, and it is especially essential that all gallery seats should be upholstered. For Concert Halls. Large areas of panelling, carpeted floors, and upholstered seats are advised for most concert halls, and the rear walls should comprise some absorbent materials, or else consist of heavily draped boxes built in. All these items tend to control reverberations. It has been found that areas of glass respond to low tones, wood panelling to middle and upper middle tones, and oil-painted canvas over wood to muffled middle tones. v Outdoor acoustics are curious. A man speaking in the open air can be heard at a greater distance if he is standing in front of a wall than if he has an open space behind him. If there is also a clear space before him that is paved, his voice will carry still better to the audience. Similarly, a building on a noisy main road that is immediately opposite a park or open space proves considerably quieter within than the adjoining premises that are opposite other buildings across the road. The reason for this is that a good proportion of the noises from the street are reflected from the fronts of the opposite buildings. The selection of a site in a busy town is therefore of not a little importance from this point of view alone.