Sound fields surrounding air-craft engines thought to be the cause of physical or mental disturbances experienced by person at close range. Laird(1932) reported that 60 decibels of noise decreased the normal secretion of gastric juice in four of five human subjects who previously had been given and Ewald meal and also caused a decrease in the normal secretion of saliva by about 40 per cent. Simth and Laird(1930) had observed that 80 to 90 decibels of noise caused a decrease in gastric motility in human beings. Vaughan and Van Liere(19400) reported a significant reduction in acid secretion with a noise having 100 decibels and 2,000 frequency in dogs with Pavllov Pouches. However, noise frequency of 600 was ineffective.
It is generally recognized that the behavior man exposed to noise, especially to disagreeable noise, shows that different persons or even the same person under different situation responds quite differently, quantitatively and qualitatively,
to the same noise.
Present study was undertaken to determine in human and in animals whether digestive function or other disorders occurred more readily with single or repeated exposure of air-craft noise.
A. Human Subject:
Thirty three healthy Korean males, having 54 to 70kg by weight, 163 to 178cm by height and 23 to 31 by age were employed in this experiment. Gastric juice collections were performed at early morning with all subjects in the fasting condition.
Six healthy mongrel dogs weighing 10 to 15kg and Albino rats weighing about 200g were used. Denervated(Heidenhain) pouches in four dogs were prepared by the technique described by Devito and Harkins. In two dogs stomach cannula was fixed simply in fundic protein without interruption of nerve supply. These dogs were
maintained with care until complete healing from surgical wound. They were fasted for 15 hours before each experiment and the collections were performed in conscious state. Rats fed with synthetic diet, were placed in the condition of repeated noise
for either short or long period and gastric ulcers were produced by the procedure described by Shay et al.(1945).
C. Choice of Noise:
F-86F jet engine sound was recorded in the distance of 3m apart from engine pipe during engine test. The sound was reproduced through amplifying Hi-Fi with speaker, which emitted 100 to 120 phon of noise. The noise was measured by the noise meter.
The background noise showed around 20 phon in this experiment. The subjects were exposed on noise for 30 min to 60min in cases of human and dog experiment and repeating noise for 60min in rats.
D. Gastric Juice Collection:
Fasting gastric juice was collected before and after exposure to noise by 15min interval in human and dog. In dog the response of meal(500g) and histamine (2mg base) were also determined.
E. Gastric Juice Analysis:
The free and total acidity of the gastric juice were measured in 1.0ml aliquots by titration of the sample with N/20 NaOH, using Topfer's reagent and phenolphthalein as indicators. Mucin content and pepsin were determined by Biuret reaction and Anson's method, respectively.
F, Stomach Motility:
Fasting gastric motility was determined with water pressure after tube with attached balloon was passed through a gastric fistula in dog and through mouth in man. The changes of water pressure was traced in Kymographic paper by means of tambour .
Results and Conclusion
A. Gastric Acid Secretion:
In Heidenhain pouch dogs the meal(500g) stimulated the production of gastric juice. The secretion lasted about 3 hours with the peak of secretion being reached in th 60 to 12min after feeding.
Following the subcutaneous administration of histamine, in either Heidenhain pouch or simple pouch dogs the peak of the gastric secretion was obserbed in the 30 to 60min after feeding. After 2 hours there was a negligible output of secretion.
Following the exposure of the noise (100-120 phon) the basal secretion of gastric juice was little changed and showed only slight increase of secretion gastric or Heidenhain pouch dog.
In 39 human subjects the resting flow and free acid content of gastric juice were 2.09 cc/min and 34.2 mEq/l. Following exposure to the noise the flow of gastric juice was lightly decreased and continued for 60min even after withdrawal of the noise. The acidity and mucin content of gastric juice were not altered by noise.
However, they can divided into 2 categories, e.g., those decreased and those increased acid output of gastric juice by the influences of noise. The former was 30% and the latter was 64% out of total subjects. It is noticed that basal secretion of those showing decreased acidity was considerably high and of those increase acidity was low.
B. Gastic Motility:
The active and regular fasting gastric peristaltic movement was greatly inhibited by the exposure of the noise in total gastic pouch dogs. Withdrawal of the noise resulted rapid recovery of the movement with light enhancemont. The gastric movement was completely inhibited by atropine. The inhibition of the gasttic
peristaltic movement by the noise in human subjects was more sensitive and more prolonged than that of dog.
C. Influence on Gastic Ulcer:
Ulcerative gastric lesions in rats were produced by the procedure of Shay et al.(1945) following exposure to the noise. Both groups having short and long term exposure to noise were divided. The occurrence of ulcer lesion was increase and the
severity of the lesion was enhanced in groups supplemented noise for either short or long period. The majority of the rats showed one or more of ulcers in the rumen and a few showed hemorrhage and ulcer lesions in grandular portion of stomach. The acidity of gastric content of control rats was ghigh than those of noise exposed animals.
The above results obtained in 소냐 experiments demonstrated that the influences of air-craft noise were not remarkable, but a considerable inhibition of gastric function were resulted in man and dog and the progress of ulcer was more or less aggrevated in rats, which lead to believe that the noise to a considerable degree are responsible for the prevalence of digestive disorders in human life.