Subjects were exposed in one ear for 5 min to «-oct band noise centered at either 2, 3, 4, or 6 kHz at 110 dB SPL. The resulting aftersensation, called "noise-induced short-duration tinnitus" (NIST) was matched for pitch and loudness in the nonstimulated ear. It was found that the pitch of NIST bears a constant relation to the frequency of the stimulus and that the difference between the equivalent frequency of NIST and the frequency of maximum threshold shift was equivalent to one critical band.

No abstract

Time-weighted average (TWA) is widely used in research and practice, in occupational health, as an index of exposure and dose. Its key element, CT, where C is concentration of contaminant and T is duration of contamination, is recognizable as Haber's rule. Neither TWA nor similar measurements have been scientifically validated, and it does not seem appropriately named. In the late 1940s and early 1950s, cautions were expressed about the scientific validity of TWA, but the specific scientific study of it did not begin until 1981. In the interim, the cautions appear to have been largely ignored. In 1985, TWA cannot be said to be scientifically valid. Uses of it often confuse dose and exposure, and take insufficient account of time as a factor. Validation of TWA may well be too complicated a scientific problem for occupational epidemiology. TWA need not be rejected for regulatory or all practical purposes, but its key element ought to be better understood, and all applications which presume its scientific validity need to be reviewed.

This paper considers the precision which may be expected in short-term serial measurements of audiometric thresholds.Twelve otologically normal young men were tested on four separate occasions at 1, 2, 3, 4, 6, 8, 0-5, and 1 kc/s. The tests were carried out in a mobile test room installed in a specially constructed vehicle chassis.The acoustic output of the audiometer and ear-phones was measured at intervals throughout the investigation. Output stability with variations of mains supply voltage and drift during the warming-up period of the instrument were also measured.It was concluded that the instrument variation had been extremely slight throughout the investigation.The estimates of variance of repeated threshold determinations on a single ear were found to be 8 5 (dB)2 at 0 5 kc/s, 6 (dB)2 at 3 kc/s, and 23 (dB)2 at 8 kc/s. Differences between consecutive determinations extended to 25 dB.These results were obtained under conditions which practically precluded all sources of variation other than that due to the inherent uncertainty of audiometric measurements. It appears to follow, therefore, that if an apparent drop in auditory threshold in one ear is to be considered as significant evidence (P = 1 %) of a real change, the difference would have to be at least The subjects were 12 male medical students in whom no ear, nose or throat pathology could be demonstrated and who gave no history of noise exposure. Attention was paid to the possibility of the subjects developing rhinitis, either coryzal or allergic in origin, during the course of the experiment. As far as is known no test was carried out on a subject suffering from either of these conditions. The possibility of a temporary threshold shift resulting from the recent use of noisy transport was also excluded by arranging to perform the tests between lectures, rather than on the individual's first arrival in the morning. Enquiry was also made concerning previous treatment by drugs with VlIIth nerve toxicity.It was considered that this group comprised otologically normal subjects as defined in British Standards 2497 (1954) and this assumption is supported by the actual audiometric results, which showed no gross departure from the normal threshold of hearing.For the purpose of this experiment it was necessary to demonstrate that the acoustic output of the audiometer did not vary during the course of the 231 on 11 May 2018 by guest. Protected by copyright.

1972). Brit. J. industr. Med, 29, 1-14. Mortality of newspaper workers from lung cancer and bronchitis 1952-66. The mortality experience of 3 485 men who worked full-time in the newspaper printing industry in London and Manchester and died in the period 1952-66 has been analysed for occupation and cause of death.There was an excess of deaths from cancer of the lung and bronchus (I.C.D. 162, 163) in printing trade workers as a whole compared with the male population ofthe region in which they worked, adjusted for age and calendar year of death. The excess was about 30% in London and about 40% in Manchester. Both these excesses are significant at the 1 % level. In Manchester, but not in London, there was a concentration of excess (about 100%) in machine room men, again significant at the 1% level. White collar workers showed no difference between observed and expected deaths in London and only a small excess (20%, not significant at the 5 % level) in Manchester.There were small deficits of deaths from bronchitis (I.C.D. 500 to 502), about 10% for printing trade workers, and 30 to 40 % for white collar workers, with little difference between London and Manchester. Neither deficit is significant at the 5% level because of the small numbers involved.This survey does not provide any evidence about the cause of the overall small excess of deaths from lung cancer, which might or might not be occupational. The larger excess in the Manchester machine room men is more likely to be due to an occupational hazard.