[Slight differences in noise stimulation and NI-TTS (noise-induced temporary threshold shift)].
This paper was attempted to study on the temporary threshold shift (TTS) at 4000cps by a 20-min noise exposure through a earphone to each of a subdivided tone, approximately 2db step, within the range of 79 to 88 phon of white noise. The change of auditory sensitivity was observed by means of Bekesy-type audiometer. Nine subjects tested were adult men with normal hearing who had well experienced the Bekesy audiometry. These results were as follows:1) Although the intensities of stimuli of tones were slightly different respectively, a noise intensity which produced a remarked rise of TTS and a prolonged recovery from it was found in all the subjects.2) A noise intensity level producing of such an elevated threshold was significantly defferent each other:No. 1 and No. 7 were found at 81db; No. 2 at 82db; No. 3, No. 5, No. 6 and No. 9 at 84db; No. 4 and No. 8 at 86db.3) Observing the recovery process over a duration of 20 min, the following was noted, that the elevated threshold after stimuli, being recovered to normal threshold, still showed the elevation in 7-9 min after stimuli were ceased. This was classified to class IV & V. These recovery types were more frequently found on 1 grade less intensity of tone than the fatiguing tone intensity producing the remarked threshold shift and prolonged recovery of it. And these recovery pattern dissappeared on the interruped threshold tone at a frequency of 4000cps.
Contribution to the Study of Auditory Fatigue
Fatigue and other effects of 3 minutes of strong (105 db) acoustic stimulation were studied. Four combinations of fatiguing sound (white noise or 2‐kc tone) and test frequency (3 or 4 kc) were each used twice for each of 24 Ss. Mean threshold recovery, functions closely resembled many of the individual functions reported by Hirsh and Ward and confirmed the phenomenon they called “bounce” however, many individual functions, like Hood's, were monotonic. Largest inter‐subject and smallest intra‐subject variability were associated with the noise/4000 combination. Ss differed considerably with respect to general fatiguability and recovery rate, and they tended to remain in the same rank order throughout the post‐stimulatory period. There was a positive but low relationship between the fatigue a S displayed under one condition and what he displayed after the same recovery time under another condition; the relationship was generally highest after the first 3 minutes following stimulation. Many individual recover...
VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission
A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of greater than 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights less than 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(sub A) approx. = 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of Omega = 13.45 deg - ((3 deg (sin(exp 2)B)). 5. We find a statistical limb darkening, which can be described by the relation (T(sub B)(alpha))/T(sub B)(0)) = 0.4 + ((0.6(cos(exp 2) alpha)) for sources with T(sub B) greater than 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater than or approximately equal to 0.5 MK), or equivalently, long-lived sources (greater than or approximately equal to 5 days) show a systematic variation of their altitude as function of the center-limb distance.