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otherwise would have to be spent elsewhere at a later stage on SST development programs. IV. RESEARCH REQUIRED This statement of research required is based upon: 1) the existing state of our knowledge resulting from past research and current work underway, and 2) the changed nature of the task with which the Committee has been confronted as outlined above. A detailed statement of our present state of knowledge, with an outline of the merits and demerits of past and existing knowledge would be needlessly redundant. Such information is readily available in the public domain.* The Subcom- mittee's evaluation of this information is conveyed either explicitly or implicitly in the following statement of work to be done. Psychoacoustic Determination of Annoying Acoustical Aspects of the Boom. Study of the effective stimulus parameters of impulsive sounds as they relate to annoyance should be continued. Some of the relations among individual stimulus variables are known; e.g., duration, peak pressure, wavefront, and so on. But, perhaps some other dimension such as spectral energy density or rise time relates more simply, directly and significantly to annoyance. If such new relations can be established they should aid greatly in the formulation of guidelines for design of future SSTs that may produce booms of a more benign nature. Simulation. Construction of several additional simulation facilities devoted specifically to human response studies is badly needed. These much needed facilities should be able to simulate faithfully both the low and high frequency features of the sonic boom. New as well as now-existing simulation facilities should be made available to qualified investigators and should incorporate design features that will permit easy change and modification. Understanding human response to the sonic boom is sufficiently important to warrant high priority for the maximum use of simulation facilities. For facilities in government laboratories, if in-house laboratory manpower is in- sufficient, contractor personnel should be sought to supplement the efforts of permanent personnel. Suitable simulation facilities could be *Many of the reports on past sonic boom research are available either from the National Aeronautics and Space Administration, Department of Transportation or Department of Commerce Clearinghouse for Federal Scientific and Technical Information. -5-
of considerable importance in determining long-term effects on sleep and irritability of repeated exposure to sonic booms of differing overpressures, shape and frequency over a long period of time. Relationship of Impulse Vibration to Annoyance. Studies of subjective reaction to impulse type vibrations should be undertaken. It is important to create a valid psychological scale of annoyance to brief vibrating stimuli and to determine the interrelation between vibration and acoustic stimuli. Several psychophysical methods, especially magni- tude estimation procedures, should be utilized to cross-validate the obtained scale. Magnitude Estimation. The psychophysical methods of matching and category scaling used in past research on the sonic boom should be expanded to include the method of magnitude estimation. The latter method provides more flexibility and more information than matching and is less dependent on context than is category scaling. Magnitude estimation should be applied to the criterion of annoyance as well as to responses like acceptability, loudness and noisiness. The first of these applications should permit an additional validation of results obtained in the past. The second would lead, hopefully, to a better understanding of the psychological components of acceptability or nonacceptability. The method should be applied both in the laboratory and in the field. Analytical laboratory studies could provide information on how loudness, annoyance, and other psychological correlates depend on the various physical parameters of the sonic boom. Field studies should aim at the sociological responses to sonic booms of different overpressures and shapes under various environmental conditions. Not all variants of the method of magnitude estimation appear equally well-suited for the evaluation of psychological responses to the sonic boom. It is there- fore recommended that future studies make ample use of experienced consultants. Effect of Sonic Booms on Behavior It is important to know more about the response of an individual to the sonic boom as a function of his ongoing activities such as skilled motor performance, conversation, daily routine, sleep at night, sleep during the day, or recovery in a hospital. These relations should be studied independently for infants, children and adults of all ages. Sleep. Since interruption of sleep is particularly annoying and detrimental to a considerable degree to everyone and particularly to middle-aged and older persons who have difficulty in sleeping, this area of ongoing activity has been singled out for detailed recommendations. -6-
Investigation of the effects of sonic boom on sleep and efficiency should be continued and extended. Even though SST nighttime overflights of the current version of the SST over populated areas may never be considered seriously, there are large numbers of people, including night workers, invalids, hospitalized patients and the elderly who sleepduring daylight hours. Among the many questions not yet fully studied, the following are particularly relevant in this field as a background for management decisions: 1. What are intensity levels of booms below which behavioral waking is unlikely? 2. Does behavioral waking adapt to repeated boom stimuli? Does it adapt differently to changes in over- pressure level or to variations in rise time? 3. Do repeated booms cause changes in the depth of sleep as judged by the electroencephalogram (EEC)? Does the simulated subject develop a chronic deficit of important stages of sleep? What is the level of boom overpressure and initial rise time at which sleep is usually not disturbed. 4. Do repeated brief awakenings of normal subjects cause behavioral changes, psychological distress or excessive fatigue? 5. What levels of simulated sonic boom aggravate existing sleep disorders? Might there be a significant subgroup in the population in whom any audible booms would cause severe loss of sleep? Social Psychological Studies of the distribution of individual responses should be conducted in such a way as to enhance our understanding of social psychological responses, to permit prediction of the responses of larger populations than those so far studied under boom exposure, and to identify special subgroups in the population whose responses may in some way be unusual. Studies in this category should generally be surveys of the sort conducted in Oklahoma City. Such studies may be possible in the near future only if military supersonic training over- flight schedules provide circumstances in which large numbers of -7-
individuals would be exposed frequently to sonic booms, and then, only if plans are made in advance so that people exposed may be questioned and their responses noted. Future surveys should continue to explore the relations of personal characteristics and personal circumstances to responses to sonic booms. Survey subgroups could include those who: think SSTs are inevitable, are associated with the aircraft industry, habitually question political authority, have a special sensitivity to noise and have a history of frequent complaints. Such knowledge is important as a basis for anticipating the probable responses of other segments of the population who may share these characteristics in varying degrees. More specifically, if the distribution of relevant personal characteris- tics and background circumstances were to be determined for the U.S. population via methods now available for rapidly conducting a national sampling survey, we could make a better prediction of the response of the total population â considered as an aggregate of individuals â than we could on the basis of even a fairly large number of separate community studies. Community studies can provide two kinds of knowledge, an understanding of the response of individual communities as such, and the consequences of individual responses in those communities. The latter knowledge will make it possible for us to extrapolate to other populations of individuals. This extrapolation can be made by ascer- taining the distribution, in such populations, of the backgrounds and characteristics that have been demonstrated to be correlated with response to booms. Studies of the distribution of responses should include a wide variety of more specific criteria beyond mere expressions of annoyance and/or tolerability; e.g., overt complaints, loss of sleep, interference with work, disturbance of other activities and so on. The extension of the criteria to be considered should be to some extent coincidental with the investigation of special subgroups of the population. Certain subgroups attract attention because of the prior expectation that they may be especially vulnerable on one or another criterion â startle, sleep disturbance, work interruption, and so on. Previous work such as that done in Oklahoma City has included the investigation of some special groups, though the findings have not been as fully reported as the findings for the population in general. Previous work also indicates that research on such groups may be especially difficult. Added efforts should be made to extend our knowledge of the effects that sonic booms have on special groups. -8-
Before planning further research we must consolidate our present understanding of the reaction of subgroups such as hospital populations, daytime sleepers, infants, old people, persons engaged in delicate and vital work (e.g., surgeons), students in classrooms, and so on. The concern for special groups should be extended, as has already been proposed, to a consideration of such populations as persons on ships at sea and in small pleasure craft, both to assess their reaction and to estimate the numbers of persons involved under different conditions. The goals of research on the distribution of responses to the sonic boom should be to predict the probable responses on several criteria, not only of the general population, but also of subgroups, especially those that might be presumed to bear an unusual burden of the costs of supersonic overflights. Such research should test also the effects of different patterns of exposure to booms; e.g., frequency versus intensity, and such specific questions as whether persons exposed to booms become more or less tolerant of them over the course of time, whether booms in a noisy community are the "straw that breaks the camel's back" or are merely one of many minor irritants. Community response studies are required because a community is a structured system whose response does not relate in a simple way to the responses of members that comprise the community. The indivi- dual character of a given community may suppress or may amplify the responses of its individual members on a given issue. In one case, failure to understand the inhibiting effects of the circumstances of a given community may lead to an unfortunate under-estimation of the costs borne by its members; in the other case, one might under-estimate the problems generated by community reactions or the reactions of organized groups that are disproportionate to what one would have predicted on the basis of a knowledge of the distribution of individual responses in the community. To study community response alone is to incur the risk of a faulty estimation of the personal costs involved. To study individual response alone is to risk a false estimation of the disturbance to the system. Each must be studied in its own right. By and large, we may assume that an estimation of the personal costs to be borne by the population will be determined mainly by survey type studies that establish the distribution of individual responses. Some estimation of the added costs and difficulties of handling the problems of society will be achieved to the extent that such surveys enable one to predict the number and vigor of complaints that may be made. Community reaction studies bear more directly on the costs and -9-
the difficulties of management that might be anticipated by estimating the number of communities that might make an official representation to their Congressional representatives, or the number that might apply for an injunction to stop overflights of the commercial SST and so on. Our knowledge of the factors influencing community responses lags far behind our understanding of individual responses â no matter how deficient one may conceive the latter to be. If we contemplate the full range of situations with which we may be confronted, a national program of research on human response to the sonic boom should include consideration of the costs that might accrue via community reactions as distinct from individual reactions to different levels of the boom. Costs from adverse community reactions might be of greater magnitude than the costs to individuals. There have, in fact, been situations studied in the past in which organized action seems to have been disproprotionate to individual costs. The ultimate objective that one might foresee is that a knowledge of community characteristics associated with response to sonic booms may make it possible, by assaying the distribution of such community characteristics in a sample of American communities that may be overflown by the SST, to assess the incidence and nature of community reactions as a whole. Problems of measurement are posed by the sonic boom issue. These problems place demands that are beyond the present state of the art. Implicit is the concept of "utility" which welfare economists have put forth as a yardstick by which monetary and nonmonetary costs and benefits can be compared. Such an ultimate yardstick is far from realization but there is every reason to believe that usable approxi- mations can be obtained in specific situations. There are, however, many opportunities for measurement which are most valuable yet fall far short of the ultimate attainment of a measure of common utility for all costs and benefits. For example, the Edwards Air Force Base experiment has increased our ability to translate the acceptability of sonic booms into equivalent levels of perceived noise for noise of jet airplanes and has given us new insight into probable public response to presently contemplated SSTs. There are similar problems of measurement in the broad range of issues involved in noise abatement and noise control of all kinds. Interested agencies of the Government ought to contemplate the possibility of supporting studies of measurement and comparison as they bear on the overall noise problem. The funding of research on reactions -10-
