Sound Without The Fury

Press, Volume XCVII, Issue 28529, 7 March 1958, Page 14

Sound Without The Fury

Anyone who has been in an empty house will remember how the slightest sound bounced back, loud and harsh.- If a room in the home has the same qualities in some degree it can usually be made more pleasant without any great effort.

For perfect room acoustics for music, live or reproduced, the services of an acoustical engineer must be obtained. Improving the quality of sound in a room, however, can be done by following a few simple principles.

All substances either absorb or reflect sound. When a room is full of glass, polished wood, and other hard surfaces, sounds will be harsh. In a room with a lot of soft furnishings, carpet, and drapes the sound will be muffled.

The live room, where sound is harsh, can be made more pleasant by increasing the size of drapes and folding them more deeply. A drape folded to half its width absorbs nearly twice as much sound as the same amount of material hung flat. Sponge rubber placed underneath the carpet nearly doubles its already fairly high sound absorption. Possibly the cheapest and simplest way of absorbing excess sound, though, is to put a panel covered with acoustic tiles somewhere on the wall. A room in which sound is unpleasantly mu (Tied can be made more live bv increasing the area of sound-reflecting surfaces in it. Dead Room If a room is reasonably dead acoustically, less noise from it will penetrate nearby rooms than would be the case with a live room. But much more can be done to keep sound where it belongs. A built-in wardrobe full of clothes insulates a wall against sound extremely effectively. Also I particularly effective is the use of vermiculite as a filler between linings of walls and ceilings. Vermiculite is a light-weight mineral which is inert chemically, fire-proof, odourless, and verminproof. As well as its soundproofing qualities it is a good neat insulator.

Mixed with cement it produces a light-weight building concrete of which one cubic foot weighs 301 b, against 1401 b for ordinary concrete. This concrete is now beoming widely used in the floors of houses.

The following table shows the percentage of sound at the pitch

of normal speech absorbed by various materials:— Acoustic fibreglass 91 Acoustic tile 85-75 Carpet with sponge rubber underneath 65-55 Draperies 55-40 Carpet and underfelt .... 35 Draperies, hung flat 30-10 Carpet without underfelt .. 25 Cork tile on concrete .... 8 Linoleum on concrete .... 4 Asphalt or rubber tile on concrete 3 Wooden floor 3 Plaster 4 Brick 3 Glass 3 Concrete 2

The Magic Word

The gramophone has become an essential part of life in the last few years, due mainly to the development of the long-playing record.

Although the magic word “hi-fi” is attached to practically anything capable of producing a sound, the quality of sound reproduction varies almost as much as price. There are four main elements in a record-reproducing system—the turntable, pickup, amplifier, and loudspeaker. They may be bpught separately or enclosed in a cabinet. The prices both of components and complete units vary greatly.

Many persons prefer to have a radiogram, with everything in one cabinet. Some of these remarkably good reproduction, in others it is only tolerable. Most radiograms nowadays contain automatic record-changers. Experts are unanimous in denouncing these-—because of their complex mechanism and the danger to record surfaces—but they sell well.

The man—it is usually a man—who wants the best possible reproduction from his records will choose separate components. This generally means a heavy 12-inch turntable, a transcription pickup, often of different manufacture to the turntable, an amplifier which may cost between £2O and £7O, and a 12-inch loudspeaker or a combination of loudspeakers which will be installed in a care-fully-designed cabinet. These components may cost from about £6O to £2OO. Almost perfect reproduction can, however, be obtained with a system costing about £BO.