794 AEROPLANE NOISE AND DEAFNESS

AEROPLANE NOISE AND DEAFNESSTHE occupational deafness of boilermakers and

of workers in similar noisy surroundings has longbeen recognised. The noise produced by certaintypes of multi-engined aircraft has been measuredand found to exceed that in boilermakers’ shops;and engine-noise is likely to become still greatelwith further increases of horse-power. It hastherefore become important to study the effects ofthese sounds on the hearing of aviators and thosewho test and tune their machines, and a usefulpreliminary survey has been made by DICKSON,EWING and LITTLER.1

Laboratory experiments have shown that loudtones at intensities up to 120 decibels above thenormal threshold, and with frequencies betweenC1 and C4, cause temporary diminution of acuityover a range of frequencies extending from thelevel of the fatiguing tone to about an octave higher.Audiograms of cases of deafness in members ofthe Royal Air Force invariably show a bilateral lossof acuity confined to frequencies above 0, andusually most definite in the region of C4. Analysis,however, of the sounds emitted by aeroplanesshows that frequencies which give the highestrelative loudness are invariably at the lower end ofthe scale ; so that, in the case of aeroplane deaf-ness, loss of acuity at the upper end of the scale iscaused by vibrations of high intensity at the lowerend. This loss at the upper end of the scale resultsin an inability to recognise consonants ; these

patients are therefore liable to make mistakes inhearing speech, but as their hearing over the rest ofthe scale is unimpaired they are not always aware oftheir deafness. The deafness is probably progressiveas long as the patient continues in his noisy occupa-tion, and aviators’ deafness must be considered tothreaten a serious and lifelong disability.Good insulation for sounds of low frequency is

particularly difficult to obtain. V. F. LAMBERT,who collaborated with Wing-Commander DICKSONand his colleagues in examining various methods ofprotecting the ears, remarks that finding a methodof completely occluding the meatus seemed on firstconsideration to be quite simple, but in practicethis was not the case. The rigid bony meatusshould be easy to occlude, but unfortunately it isvery sensitive and intolerant. The cartilaginousmeatus is more tolerant, but it is mobile and themovements of the jaw are readily transmitted to it.The substance to be used as a plug must be softenough to mould into position and to fit snuglydespite the movements of the jaw. LAMBERTfound dental stent too hard to fit tightly during thejaw movements ; neither Plasticine nor a heavyfluid in a soft rubber container proved suitable,but a plug of cotton-wool smeared with Vaselinewas quickly and safely applied and efficient. He

says that the usual flying helmet, firmly strappedso that the telephones and their holders closelyseal the ears, gives good protection, and this is con-firmed by audiograms of three pilots with manyhours’ flying to their credit, who wore helmets and1. Dickson, E. D. D., Ewing, A. W. G., and Littler, T. S.,

J. Laryng. September, 1939, p. 531.

showed no deafness. Protection of the ears

appears to diminish, if not to eliminate, the risk ofimpairment of auditory acuity, and seeing that thereis a real danger of permanent deafness if this pre.caution is neglected, steps should be taken toensure that all pilots while flying and mechanicswhile tuning engines use either an effective ear plugor a carefully fitted helmet.

TREATMENT FOR BED-WETTINGSOME of our country towns have lately come to

have a Continental look ; for every morning everywindow is filled with bedding hung out to air in thesunshine. The scene is cheerful, but the house-holders are depressed; for the habit of bed-wetting,in guests who are likely to stay a long time, is aserious tax on hospitality, especially where thehosts have no large reserve of bed-linen. Some-what unexpectedly, enuresis has proved to be oneof the major menaces to the comfortable disposi-tion of evacuated urban children ; and, though itshould diminish as the children begin to feel them-selves at home, its very existence defers thisdomestication. It alienates affection which maybe the child’s main need. Hence even the most

superficial treatment will be legitimate if it breaksthe vicious circle by removing the symptom, and ata time of widespread domestic crisis we make noapology for offering a few dogmatic opinions andrecalling some of the traditional remedies.

If a child over three years old cannot hold hiswater, the child and the water should be examined.After such general disorders as mental defect andhypothyroidism have been excluded, a searchshould be made for irritable foci in the genitalia,particularly balanitis, vulvitis, and meatal ulcera-tion. Urinary examination is important chiefly forthe discovery of pyuria-a common cause, or clueto the cause, of acquired enuresis-and a drop ofuncentrifuged urine should therefore be looked atunder the microscope. In the absence of pus andsugar it may be discovered that the urine is abnor-

mally acid or alkaline, and potassium citrate or acidsodium phosphate may be accordingly prescribed;, ;.which if it does no good will at least do no harm.As a rule, the result of these investigations will be-nothing more than the conclusion that one has to-deal with functional enuresis. When this decisionhas been made there is much to be said for turning-the patient over to a paediatric psychotherapist;but such an one is not to be found in every hedge-row, and in his absence good results can often begot by simple means. Dr. HECTOR CAMERON has.said that " functional enuresis may be cured byanyone who is confident of his own powers toachieve success and who can communicate thatconfidence to the child." The parent, however,must be made to share the doctor’s confidence andmust be additionally assiduous ; so it is to behoped that foster-parents will be less likely thanindulgent mothers to resign themselves to the child’s"weak bladder," or to his being " too small"

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or " too delicate " to be trained. If the parentor guardian believes that (in Mr. CHURCHILL’Sinspiring phrase) " we have only to persevere-to conquer," she will communicate her belief. She-