Perceptual constancy in auditory perception of distance to railway tracks

Distance to a sound source can be accurately estimated solely from auditory information. With a sound source such as a train that is passing by at a relatively large distance, the most important auditory information for the listener for estimating its distance consists of the intensity of the sound, spectral changes in the sound caused by air absorption, and the motion-induced rate of change of intensity. However, these cues are relative because prior information/experience of the sound source-its source power, its spectrum and the typical speed at which it moves-is required for such distance estimates. This paper describes two listening experiments that allow investigation of further prior contextual information taken into account by listeners-viz., whether they are indoors or outdoors. Asked to estimate the distance to the track of a railway, it is shown that listeners assessing sounds heard inside the dwelling based their distance estimates on the expected train passby sound level outdoors rather than on the passby sound level actually experienced indoors. This form of perceptual constancy may have consequences for the assessment of annoyance caused by railway noise.Full Tex

Solution syntheses of unsupported Co(Ni)-Mo-S hydrotreating catalysts

Highly dispersed Ni(Co)-Mo-S sulfides were prepd. by simple room temp. soln. reactions using nickel or cobalt salts and thiomolybdate precursors in the presence of nonionic surfactants. The products were characterized by X-ray powder diffraction, sp. surface area measurements, and scanning and transmission electron microscopy. The evolution from amorphous pre-catalysts to highly dispersed sulfide catalysts during the activation step was studied by thermal anal. Extended X-ray absorption fine structure measurements were carried out to elucidate the chem. environment of the transition metals in the precursors and the sulfided catalysts. The specific catalytic activities of the Ni(Co)-Mo-S systems in the hydrodesulfurization of thiophene and 4,6-DMDBT were up to six times higher than those of com. alumina-supported systems

Solution preparation of the amorphous molybdenum oxysulfide MoOS2 and its use for catalysis

Acid condensation of aq. MoO2S2-2 anion yields amorphous MoOS2 oxysulfide. This compd. possesses tubular morphol. and when freshly pptd. is sol. in polar orgs. such as acetone and ethanol. The ensemble of characterizations (IR, UV-visible, EXAFS spectroscopy) suggests that it contains cyclic or short linear oligomers of neutral molybdenum (V) oxysulfide MoOS2 core. Thermal decompn. of MoOS2 under inert atm. leads to the formation of a mixt. of MoO2 and MoS2 phases. Promotion of MoOS2 with cobalt followed by sulfidation leads to highly active HDS catalysts