The Hum

Urban man lives with a hum always in his ears. During his working hours, he is subjected to the distant noise of traffic, the whistle of the air conditioner, the hum of the fluorescent lighting. At home, the washing machine and the dishwasher rumble, radios blare.

Thunderous Chirp. Far from being alarmed, acoustical engineers today are in favor of the low steady hum. "There should be an unobtrusive noise, constant and surflike," says Robert B. Newman, a partner in the Cambridge. Mass., acoustical engineering firm of Bolt, Beranek & Newman, Inc. Without it, the slightest sound can prove enormously distracting. Typical is the commuter who reads a book amid the accustomed clatter of the 5:42, yet is shaken out of bed when a robin chirps in the silence of a country morning.

"Silence is the lack of noise," argues Newman; "quiet is the lack of distraction." Of the two, quiet is preferable. "A certain amount of noise is necessary to retain our sanity," agrees Psychologist George A. Talland of Massachusetts General Hospital's Psychiatric Research Laboratories.

According to current engineering theory, quiet is created by adding noise. Such background noises as the soft buzz of a fluorescent light or the slight hiss of an air cooler do not inhibit concentration (whereas the sound of voices or footsteps does). If background noise in an office averages 20 decibels (the unit for measuring sound) and distracting noise 30, the best solution is not to add expensive soundproofing but to increase the background noise by 15 or more decibels. In a Rhode Island hospital, when doctors complained that conversations carried from one office to the next, a pencil-sized cylinder was installed in the air-conditioning outlets. "The resulting steady whoosh raised the level of background noise and made the offices quieter--freer of distraction," said Newman. At M.I.T., when the library's noisy air blowers were turned off, students looked up whenever a phone rang or someone checked out a book.

Everyday Din. While it is known that too much noise causes fatigue, irritability, even loss of sexual desire, nobody is yet certain of the effects of the drone of decibels that 20th century Americans have come to accept as normal. "Ears are not damaged by the normal sounds of life," says Newman. But some disagree. Audiologist Moe Bergman, director of the Speech and Hearing Center at Manhattan's Hunter College, studied a group of African tribesmen who never heard any outside noises but jungle sounds, compared his findings with a study of a group of Angelenos who worked in relatively quiet areas (no loud industrial noises) but were naturally subjected to such everyday sounds as air conditioners, wheezing refrigerators and furnace fans. His conclusion: the Africans' hearing deteriorated only slightly as they aged, but the Californians' "changed grossly" for the worse.

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