AEROPREPARED STATEMENT OF LEO FOX, PH. D., DIRECTOR, NAUTICAL LIFE SCIENCES DIVISION, OFFICE OF ADVANCED RESEARCH AND TECHNOLOGY, NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

INTRODUCTION

The growth of transportation systems, particularly air transportation, has been spectacular in the 20th century, especially since the end of World War II. This phenomenal growth has been a major influence in altering modes of living throughout the world. It has increased individual mobility and exposed great numbers of people to experiences and environments formerly reserved for only the most affluent. It has added to the wealth of those nations which, because of their advanced technology and great productivity, have been in the forefront of this transportation boom. It has also helped to bring progress to backward nations. However, as with other forms of progress, advancement in aeronautical systems has been responsible for producing a variety of problems and disadvantages for man as an operator and a passenger of these systems, and as a member of the community at large. As aeronautical systems become more complex so will the related human problems. In the past, in the advancement of aeronautical systems, major emphasis was placed on the development of hardware to meet certain physical specifications. Only secondary consideration was given to insuring that the assigned role of the pilots and crews was within their performance capability. Moreover, the physical and psychological effects that new aircraft systems might have been expected to have on passengers and the community in general were only considered after a prototype vehicle had been constructed.

In other words, our capability to utilize man efficiently and our understanding of how man is affected by the aeronautical environment has not kept pace with the great advances we have made in the engineering of electronic and mechanical systems.

In recognition of this disparity, the Office of Advanced Research and Technology has established the Aeronautical Life Sciences Division to conduct required research and to advance technology relative to man's role in advanced aeronautical systems, including subsonic aircraft such as the STOL, supersonic transports, and in the future with hypersonic transports.

The objectives of the Aeronautical Life Sciences Program are to determine the limitations and adaptation of man relative to aeronautical environments; to develop methods and equipment to enhance human performance and safety in aviation systems; and to advance the state-of-the-art of aeronautical simulation technology for application to air and ground personnel training and proficiency maintenance and to aviation-related physiological and psychological research. The program is divided ito three elements: Environmental Effects, Man Systems Technology, and Simulation Technology. Figure 1 shows a typical example of research in each of these program elements. The objectives of these elements

are:

Environmental Effects. To obtain quantitative information on human annoyance and physiological damage due to aircraft noise and vibration; to measure the physological and psychological effects of other stresses due to aviation systems such as fatigue, desynchronosis, disorientation and visual aberrations.

Man Systems Technology.-To enhance man's performance as an operator and insure his safety and comfort as a passenger in aeronautical systems by optimizing man's role in our traffic control systems; by defining man's requirements for flight displays and controls; by developing workload standards; and by improving aircraft seats, restraint systems, protective equipment and environmental control methods.

Simulation Technology.-To maximize the utiltiy of aeronautical simulators by optimizing the visual, motion, aural, and tactile inputs to the users and by analyzing the requirements for and degree of achievement of simulation fidelity.

Advanced aircraft systems produce an environment both inside and outside the vehicle which affects man physiologically and psychologically. Some of the elements of this environment are noise, vibration, increased acceleration, increased complexity of operations, and rapid traversal of time zones. These have resulted in physiological changes such as fatigue, desynchronosis and disorientation, and increased psychological stresses, such as increased workload and altered performance. For aviation, the primary environmental pollutant is noise, and aircraft noise is already inhibiting growth in some areas.

COMMUNITY REACTION TO AIRPORT NOISE

Aircraft noise has become increasingly prevalent in American communities in the last 10 to 15 years as a result of advances in aviation technology and increased travel. Concomitant with the increase in airport noise has been a public awareness of and an annoyance reaction to this phenomenon. This has sometimes culminated in complaints or most vigorous opposition to airport operations. Consequently, a seven city study, conducted for NASA by Tracor, Incorporated, was begun a number of years ago to extend knowledge in the area of community reaction to airport noise. The results of a preliminary analysis of a portion of the data were reported last year.

Although this survey included a description and measurement of aircraft noise, it went beyond these parameters and investigated the significance of social and psychological factors in the shaping of individual and community response. The NASA-Tracor Seven City Study was completed in the second half of CY 1970. In the seven cities (Boston, Chicago, Dallas, Denver, Los Angeles, Miami, and New York), a total of 8207 interviews were obtained. Most of the respondents in each city were selected randomly from sample areas under flight paths and areas extending to 10 or 12 miles from the center of the airport. In addition,

some were selected from lists of noise complainants or from the membership of an anti-noise organization. Noise exposure for each respondent was ascertained from acoustical measurements and air traffic data. A total of over 10,000 flyover noise signatures was recorded and analyzed.

Results of the study enhanced the understanding of annoyance and complaint and their relationship to the noise produced by air traffic. The study allowed for comparison of the many existing formulations of noise parameters by using comprehensive physical and social data collected in airport communities. Two ways of accurately evaluating annoyance in exposed communities have been developed. One method permits the state of annoyance to be estimated from complaint information. Another more detailed method permits estimation of individual annoyance using a predictive equation. The latter equation and the underlying analyses also explained quantitatively for the first time the differences in annoyance observed between individuals subject to the same noise exposure. The final report has been well received by the DOT and FAA Noise Abatement Program Offices and the Interagency Noise Abatement Program Committee. The major conclusions of the study may be summarized as follows:

1. Estimation of annoyance using noise exposure as the sole predictor is rather poor. The inclusion with noise exposure of certain attitudinal or psychological variables affords good prediction of individual annoyance. An equation was written which predicts individual annoyance with good accuracy.

2. Within certain limits, the number of highly annoyed households in a community may be estimated from the numbers of complainants.

3. Adjusting for the noise attenuation of the house lowers the correlation between exposure and annoyance; people appear to react to noise as perceived outdoors rather than indoors.

4. There is a substantial difference between predictors of annoyance and predictors of complaint: predictors of annoyance are primarily physical/attitudinal; predictors of complaint are primarily physical/sociological.

5. Complainants are not more sensitive to noise than random respondents. The complainants are less annoyed with usual sources of neighborhood noise except for two items-aircraft and sonic booms. On the average, complainants, in comparison to members of the random samples, tend to live nearer the airport, have higher noise exposure, and to be older, more educated, and more affluent. They also display a higher awareness of, and negative attitude about, aircraft operations. On the basis of a very limited sample, members of noise protest organizations tend to be very similar to complainants in such characteristics.

6. Alleviation of aircraft noise annoyance by "house attenuation" methods and techniques does not appear to be feasible, except possibly in special cases. The seven city study is being followed by a study designed to determined community reaction to aircraft noise in smaller cities. The cities chosen are Chattanooga and Reno. Tracor, Incorporated, is continuing with final interviewing, noise measurements, and data processing. A final report should be available by the end of this calendar year.

The Federal Aviation Administration and various airport authorities are planning to use the data obtained from this study in conjunction with other information to aid in their decisions on the cut-off point for flight operations. The Housing and Urban Development Department plans to utilize this type of data for land planning purposes around airports. This information will aid in selecting types of structures and assessing economic effect on property in areas with particular noise characteristics generated by aviation operations.

SUBJECTIVE EVALUATION OF VTOL AIRCRAFT NOISE

The Boeing Company Vertol Division is currently conducting a study for Langley Research Center to evaluate the subjective acceptability of VTOL aircraft noise. This study is designed to define acceptability criteria for VTOL aircraft in terms of noise control requirements.

The investigative technique relies on the use of magnetic tapes to simulate the noise from tilt wing and tandem rotor aircraft, such as those shown in Figure 2. The sound spectra are varied to simulate the noise from such aircraft at various distances. During the subjective tests, VTOL sounds are interspersed with those of conventional jet aircraft, which serve as reference points. The tests approach a real-life situation in that subjects are performing tasks or are in leisure environments as shown in Figure 2. They rate each noise on an absolute basis of annoyance or interference with work or leisure activity.

The results of the Boeing-Vertol study will be used to define VTOL noise criteria in terms of subjective threshold values for annoyance or intrusiveness.

DISTURBANCE OF SLEEP BY SUBSONIC JET AIRCRAFT NOISE AND SONIC BOOMS The Stanford Research Institute, under contract with the NASA Langley Research Center, conducted studies on the disturbance of human sleep by subsonic jet aircraft noise and simulated sonic booms. Jet noise tests were carried out using actual jet aircraft flying over the subjects' location at low altitudes. Sonic boom testing was accomplished using a specially developed simulator. These studies have provided data on children (5 to 8 years of age), on middleaged men (50 years of age), and on old men (about 72 years of age).

Results of the program indicate the sleep of children tends to be essentially unaffected by either simulated sonic booms or subsonic jet flyovers. The noise intensities ranged from 0.63 to 5.0 psf for sonic booms and 101 to 119 PNdB for flyover noise, as measured outdoors. Using the same intensities for middle-aged and old men, it was found that 18 percent of middle-aged men were awakened by boom and flyover noise, while 32 percent of the older men were awakened.

In addition, some members of the middle-aged group had a high sensitivity to noise during sleep. This middle-aged high sensitivity group was found to be about ten times more likely to be awakened by sonic booms or flyover noise than the middle-aged group of low sensitivity.

By contrast, men in the old-aged group who exhibited high sensitivity were only about twice as likely to be awakened by the stimuli as those who showed low sensitivity.

Finally, the study demonstrated that on the average both middle and old-aged groups are awakened as readily by sonic booms of 2.0 psf as by subsonic jet flyover noises of about 110 PNdB.

The Department of Housing and Urban Development is planning to utilize the data obtained from this study to aid in land planning around airports.

RIDE COMFORT CRITERIA

Public acceptance and use of transportation systems involves many factors. A principal one is ride comfort. It is a complex subject involving a variety of physiological and psychological factors which can vary substantially between or within categories of passengers. As previously reported, a Langley Research Center study has concentrated on the vibration environment of vehicle passenger compartments, since vibration is believed to be a principal factor in defining the quality of ride comfort. Other factors will be considered in subsequent phases of the program.

Figure 3 shows the various vehicles studied to date. The type of vehicles involved include a station wagon, a Canadian National Turbo-train, a V/STOL aircraft (XC-142, a CTOL aircraft (Boeing 727), a helicopter (OH-4A), a STOL aircraft (McDonnell-Douglas 188), an auto-carrying ferry boat, and a pneumatic rubber-tired subway train (in Montreal system). The portable instrumentation developed for measuring the vibration spectrum, including amplitude, frequency, wave shape, and exposure time, is shown in the center photograph in Figure 3. This instrumentation measures and records the relatively low-level vibration characteristic of transportation vehicles in the low-frequency, 0-30 Hertz, regime. Vibration values were measured during complete trips of the vehicles involved. In addition to values obtained during cruise, peaks were recorded during take-off and during the impact of aircraft landings.

The data indicated that the roughest part of the ride in aircraft can, as might be expected, occur for non-cruise conditions. Over and above that, however, the data showed vibrations in the lateral and vertical degrees of freedom appear to have significant influence on ride comfort at vibration levels as low as, or lower than, 0.1 G acceleration. Of all vehicles studied, the jet transport had the lowest vibration levels. Helicopter and STOL-type vehicles, however, had considerably interior vibration characteristics. These vehicles are likely candidates for programs aimed at reducing vibration.

Last year, Langley Research Center, using the specially developed portable equipment, made vibration measurements on the Metroliner on a trip from Washington to New York and return. Prior to these measurements, there was no vibration data available. The input of this information was a factor in the decision of the Penn Central Railroad to make improvements on the road bed between Washington and New York. This should result in a much more comfortable ride.

A new effort planned at Langley is a ride comfort simulator (Figure 4). The vibration data obtained in the field have been used to formulate specifications for the simulator. It will be employed to study effects of both single and multiple degrees-of-freedom vibration inputs on ride comfort and can also be used to measure subjective reactions to other environmental factors, such as noise. Through correlation of laboratory and field experiments, it should be possible to derive meaningful ride-comfort criteria.

EFFECTS OF VIBRATION AND NOISE ON PERFORMANCE

The literature is replete with studies of human performance under noise stimuli. However, few studies have examined performance in a noise environment with the superimposition of other stresses such as are encountered by aircrews in flight. Today, pilots flying VTOL commercial routes spend about eight hours each day in the cockpit. Many of the flights are under Instrument Flight Rules (IFR), and the crews log nearly 30 landings and take-offs each day. Earlier studies have shown that operational VTOL flight environments normally do not degrade pilot performance under Visual Flight Rules. However, there is the possibility that performance degradation may occur when the increased workload of IFR flight is superimposed on the vibration and noise environment of VTOL aircraft.

Sikorsky Division of United Aircraft Corporation, under contract with the Langley Research Center, is currently studying the problem of the combined stresses of vibration and noise on pilot performance by simulating a VTOL flight plan under IFR conditions. IFR was chosen because flying this type of approach pattern requires close to maximum effort on the part of each crewmember.