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from one individual to another , and depends on such factors as age , <br /> 1 <br /> attitude towards the noisemaker , fear , and even socioecionomic status . <br /> In a recent study [ 5 ] comparing the data from 11 social surveys <br /> conducted over 13 years in 6 countries , the percentage or people highly <br /> annoyed was determined as a function of Ldn . These surveys showed that <br /> people who were questioned at different times in diffei.ent countries <br /> reacted to noise with surprising similarity. Figure 11 shows the <br /> average results of the surveys , as well as the results of the individual <br /> questionnaires . The range of response occurring at a givennoise level <br /> reflects human nature . In any group of people , you sill find some <br /> members are annoyed by sounds others won' t even notice . <br /> But when does annoyance result in action? And ho;■T much action? <br /> The answer is : Response cannot be pinpointed , but the rainge of response <br /> can be quite well predicted. One widely based relationship between <br /> noise and community response and noise exposure i he result of <br /> analyzing 55 case histories of impacts from various noist sources [6 ] . <br /> 411 The relationship is shown in Fig. 12. Because of the wide variety of <br /> situations represented by the 55 different cases , the data have been <br /> adapted to the standard set of conditions noted in the! figure . The <br /> major normalizing factor is that all environments were adjusted so that <br /> the residual noise level -- the noise that you hear , but! whose source <br /> you cannot determine -- was at the level found in urban residential <br /> areas . This is L dn 60. <br /> When the residual noise level differs from that found in urban <br /> residential areas , the impact of aircraft noise will also!differ. For <br /> example , in quiet residential areas ( an Ldn of 50 , 10 dB below urban <br /> residential) the impact is as if the aircraft noise were 10 dB higher . <br /> From Fig. 12 , we would expect aircraft noise at Ldn 65 in a quiet <br /> residential area to cause the reaction of aircraft noise at L dn 75 in an <br /> urban residential area -- vigorous community reaction <br /> 411 <br /> 28 <br /> ,4 :r • <br />