Norman L. Carter

Human response to environmental noise: The role of perceived control

Negative impacts of noise exposure on health and performance may result in part from “learned helplessness,” the syndrome of deficits typically produced by exposure to uncontrollable events. People may perceive environmental noise to be uncontrollable, and several effects of noise exposure appear to parallel “learned helplessness” deficits. In the present socioacoustic survey (N = 1,015), perceived control over aircraft noise correlated negatively with some effects of noise (though not others). Furthermore, these effects were better predicted by perceived control than by noise level. These observational data support the claim that “learned helplessness” contributes to the effects of noise exposure.

Placebo-Controlled Biofeedback Blood Pressure Effect in Hypertensive Humans

The role of biofeedback in blood pressure control remains ill-defined because of nonspecific (placebo) effects, small study numbers, and the technical limitations of continuous pressure feedback. Clarification of its potential is awaited by those seeking a nonpharmacological approach to blood pressure control. This study examines the capability for systolic pressure lowering of 5 mm Hg or more using continuous pressure feedback in a statistical sample of untreated, well-characterized, mildly hypertensive individuals. Subjects were randomized in a double-blind study to active or placebo biofeedback. Placebo consisted of a modified contingency approach, using a partial disguise based on a digital high pass filter with 15 elements. Blood pressure-lowering capability was assessed during two laboratory sessions. Continuous visual feedback resulted in 11 of 28 subjects on active treatment and 12 of 28 on placebo treatment lowering their systolic pressure by 5 mm Hg or more (11 +/- 5.6 and 12 +/- 8.4 mm Hg, respectively; P = NS). Prestudy pressure was well-matched (153 +/- 9/97 +/- 4 and 154 +/- 8/98 +/- 4 mm Hg, respectively). An initial small difference in diurnal profile did not change. These findings indicate that among mildly hypertensive individuals, almost half can lower systolic pressure at will for short periods. This capability is independent of the real or placebo nature of the feedback signal. We conclude that there is no specific short-term biofeedback pressure-lowering capability in hypertensive individuals. Further exploration is needed to determine whether specific components of the placebo effect can be delineated, whether personality characteristics influence the response, and whether further biofeedback training can alter the outcome.

Predicting habituation/adaptation to aircraft noise

Whether or not people habituate and/or adapt to a negative soundscape remains a contentious issue. The Sydney Airport Health Study has involved interviews with residents before, soon after, and several years after the runways were reconfigured. Noise increased in some low‐noise areas and decreased in some high‐noise areas (while other areas remained highly exposed and unchanged, or minimally exposed to aircraft noise). Of the pre‐reconfiguration sample, 23.6% reported getting used to the noise. This paper examines the factors which predict who will get used to the noise and who will not, by regression against a number of predictors: noise exposure, sensitivity, attitude, personality, age, gender. The post‐reconfiguration studies also allow examination of the speed with which reaction changes with changed exposure, and the factors which predict changes in reaction. Underlying mechanisms other than adaptation and habituation are considered.

The contribution of noise to perception of neighborhood satisfaction, and the probability of leaving the area

When the runaways at Sydney Airport were reconfigured, noise increased in some low‐noise areas and decreased in some high‐noise areas (while other areas remained highly exposed and unchanged, or minimally exposed to aircraft noise). Residents were surveyed before (N=1015), immediately after, and several years after the reconfiguration. This data set allows consideration of the extent to which ratings of the neighborhood are determined by noise versus other factors (parks, air pollution, safety). Residents were also asked whether they would consider moving because of the noise. From the follow‐up data we examined which features of the residents satisfaction with the area and the noise, as well as features of the residents themselves (noise sensitivity, general sensitivity, personality, home ownership) predicted considering moving and moving. These results address the issue of the importance of soundscape in residential satisfaction, relative to other factors.