[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.
Loudness Patterns—A New Approach
When a sound enters the ear it sets up a vibration pattern along the basilar membrane. This vibration pattern initiates nerve pulses which travel along the eighth nerve to the brain, where a second pattern of neural activity results. Two general methods may be used to study these patterms: (1) the objective measurement of cortical potentials by the electro‐physiologist, and (2) subjective measurements such as masking and fatigue effects. The present paper is based on the latter procedure in which the results of loudness and fatigue tests have been combined to give patterns of cortical activity in terms of millisones per kappa‐band. Use of fatigue patterns permits employment of a low level probe tone which overcomes the difficulties formerly experienced with artifacts in masking patterns due to beats and distortion products.
Pioneer 10 Observations of the Ultraviolet Glow in the Vicinity of Jupiter
A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-α, the surface brightness is about 10,000 rayleighs.