The Effects of High Intensity Noise on Human Equilibrium
Abstract : Five experiments were conducted on the effects of broadband, high intensity noise on human equilibrium. The ability of subject to balance on narrow rails was measured during exposure to the noise; and immediately after termination of the noise. Four different noise conditions were used in each experiment: control, 120, 130, and 140 dB (re. 0.0002 dyne/sq cm). In the first experiment subjects wore earmuffs and earplugs; in the second, only earplugs were worn; and in the third experiment, subjects wore earplugs and one earmuff to produce an asymmetrical exposure. At an ambient level of 140 dB, a detrimental effect was obtained in all three experiments. At lower intensities of noise, there were performance decrements only for the asymmetrical exposure. In the remaining two experiments, conducted after termination of the noise, detrimental effects were obtained for asymmetrical auditory exposure but not for equal auditory exposure. The results of these experiments are interpreted as a possible quantitative demonstration of the direct effect of high intensity noise on the vestibular system.
Observations on Disturbances of Equilibrium and Other Symptoms Induced by Jet-Engine Noise
Introduction IN a previous report (Dickson and Watson, 1949), mention was made of the occasional occurrence of the symptoms, unsteadiness, dizziness and lack of concentration in personnel working with turbo-jet aircraft. These disturbances were noticed chiefly in the vicinity of the impellor close to the, air intake at the fore end of the engines. The appearance of such subjective sensations seemed to be produced infrequently and erratically. Injudicious press reports of possible harmful effects resulting from exposure to ultrasonic frequencies generated by jet engines led to a number of purely psychological disturbances being experienced by jet personnel. At first sight therefore, the assumption that they were psychological in origin provided a reasonable, though not altogether satisfactory explanation. Reference to the literature on this subject has revealed no clear conclusions. A transient vestibular irritation induced by standing in close proximity to turbo-jet engines when run at certain speeds has been experienced by many observers, including the present writers. That this phenomenon is due solely to the presence of ultrasonic waves as was first suggested seems unlikely. It is well known that stimulation of the vestibule can be caused by sufficiently loud acoustic stimuli. Frequency analyses have shown that sounds within the normal range of audibility are generated by jet engines at sufficiently high intensities to provide an adequate stimulus to the labyrinth, even in normal individuals. Some reports, nevertheless, indicate that frequencies above the normal sound range can also produce similar effects. Ultrasonic spectra, however, reveal that during the test bed running of jet engines, frequencies above the range of audible sound are of so low an intensity as to be thought incapable of causing deleterious results.
An Internet-based Real-time Heavy Rainfall Display System
A new storm warning system, which can be accessed through the Internet and by cellular phones is described. At the time of a heavy rainfall for disaster prevention, it is important that every resident understand how heavy is that rainfall. A real-time heavy rainfall display system designed for all of Japan provides such information (http://www.disaster-i.net/rain/). In that system values for 1-hour precipitation, 24-hour accumulated precipitation, etc. are displayed at every observatory. Advantages are that not only the latest observations but differences from the historical highest records can be seen. Almost all information is displayed by characters so that users have easy access to the system even when the communication network is crowded. Access date for the six months after the system opened shows that the average daily number of accesses of the top page was 306, and the largest number 3078. The maximum number for daily access to all the pages was about 21,500. This is about 2% of the number obtained on the same day for a similar system operated by the Ministry of Land, Infrastructure and Transport (http://www.river.go.jp/).