Quiet Room, Without View

Press, Volume CII, Issue 30043, 30 January 1963, Page 16

Quiet Room, Without View

This small room, in which Mr M. Rodda, a lecturer in psychology at the University of Canterbury is sitting, is probably the quietest place in the country. Last week, noise equivalent to the sound directly behind a four-jet aircraft was created outside but, with its double-doors closed, only a whisper was heard inside the room. For its studies of hearing, speech, and sensory deprivation the psychology department needed a room free of external noise, but not so “dead” that it would emotionally disturb persons undergoing test. An anechoic room is the name given to one totally sound-proofed. The Canterbury University Engineering School has one of these but its properties are such that a person under examination might suffer acute claustrophic effects and panic.

Mr Rodda designed this room on experience he gained in building one at Durham University and he believes he has achieved, near perfection for his needs.

“We need just enough background noise to keep the subject happy,” Mr Rodda said. Under normal conditions of exterior noise, a person in this room hears it at 29.9 decibels. In a study library, where silence is imposed, the average noise level is 38; normal speech rates 40 to 50; street soiJnds at 80 to 85; and a big jet aircraft (close up) at 115 to 120.

Applying “white noise" and “pure tones” through a double arc of 20 loudspeakers outside the room, the psychology staff built up a noise level of 110 decibels this week. It was heard blocks away. Inside the room it was recorded at 32 decibels. In designing the room, four basic principles had to be taken into account: heavy materials are usually better sound insulators; materials good in reducing the reflection of sound are not so good as insulators of sound; to reduce noise effectively such a room should be structurally isolated from the ground and any adjoining building; laminated construction gives better sound-proofing properties than solid. Foot-thick Walls So Mr Rodda arranged that the room should be set on a separate concrete base and the room was then fixed on an elaborate system of mountings which eliminate direct contact with the ground and consequent vibrations from the street. The room virtually floats. The foot-thick walls, ceiling and floor contain 12 layers of fibreglass, softboard, fibrous plaster, and acoustic tiles. The double doors, similarly constructed, have a foot of air space bertween them. This air is also a good insulation. The only link with the outside world is by a communication panel wired for headphones and microphones

through which tests will ba applied and answered. The wiring zig-zags through tight seals to exclude other noise. There is no ventilation because to install it without admitting sound would ba very costly. Soda lime will remove impurities from the air so that a subject could stay in the room for an hour, if need be, without discomfort.

Even with the safeguards against claustrophobia, it is possible that some subjects may be suddenly overwhelmed by a desire to get out. The long handle shown in the picture is duplicated on the inside and win instantly release the refrigerstor-typs latch.

Mr Rodda bqlievez that this is the only room in New Zealand adequate for the truly-scientific testing of hearing which is his present special study, but it will be used by the department also for a whole new range of psycho-acoustic research.

Rams Sent By Air.—Yesterday morning 42 rams were gathered up to be loaded on to a National Airways Corporation DC3 freighter for the first flight of stock from Gore's new airfield at Charlton yesterday afternoon. Hie

consignment included rams from the Southern Provinces Stud Fair in Gore on Friday and others secured by northern buyers by private treaty. —(PA.)