BackgroundWhen stimuli are presented over headphones, they are typically perceived as internalized; i.e., they appear to emanate from inside the head. Sounds presented in the free-field tend to be externalized, i.e., perceived to be emanating from a source in the world. This phenomenon is frequently attributed to reverberation and to the spectral characteristics of the sounds: those sounds whose spectrum and reverberation matches that of free-field signals arriving at the ear canal tend to be more frequently externalized. Another factor, however, is that the virtual location of signals presented over headphones moves in perfect concert with any movements of the head, whereas the location of free-field signals moves in opposition to head movements. The effects of head movement have not been systematically disentangled from reverberation and/or spectral cues, so we measured the degree to which movements contribute to externalization.Methodology/Principal FindingsWe performed two experiments: 1) Using motion tracking and free-field loudspeaker presentation, we presented signals that moved in their spatial location to match listeners’ head movements. 2) Using motion tracking and binaural room impulse responses, we presented filtered signals over headphones that appeared to remain static relative to the world. The results from experiment 1 showed that free-field signals from the front that move with the head are less likely to be externalized (23%) than those that remain fixed (63%). Experiment 2 showed that virtual signals whose position was fixed relative to the world are more likely to be externalized (65%) than those fixed relative to the head (20%), regardless of the fidelity of the individual impulse responses.Conclusions/SignificanceHead movements play a significant role in the externalization of sound sources. These findings imply tight integration between binaural cues and self motion cues and underscore the importance of self motion for spatial auditory perception.

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Effects of hearing-aid dynamic range compression on spatial perception in a reverberant environment The Journal of the Acoustical Society of America 141, 2556 (2017) Abstract: Hearing-aid wearers have reported sound source locations as being perceptually internalized (i.e., inside their head). The contribution of hearing-aid design to internalization has, however, received little attention. This experiment compared the sensitivity of hearing-impaired (HI) and normal-hearing listeners to externalization cues when listening with their own ears and simulated behind-the-ear hearing-aids in increasingly complex listening situations and reduced pinna cues. Participants rated the degree of externalization using a multiple-stimulus listening test for mixes of internalized and externalized speech stimuli presented over headphones. The results showed that HI listeners had a contracted perception of externalization correlated with high-frequency hearing loss.

place, the propionic acid is held strongly. Propionic acid molecules not finding a strongly interacting site move on rapidly. This phenomenon contributes to the peak broadening and tailing so greatly manifest with propionic acid. As the size of the sample of propionic acid is increased, the limited number of strongly interacting sites becomes saturated; and the bulk of the propionic acid moves on more rapidly, thus resulting in the decrease in 7, observed. Effects of this type have been reported by Ottenstein (9).Column Poisoning. Previous work (/) has shown that 0.1µ samples of the test compounds injected successively into the asphalt column did not change the value of the interaction coefficient. This suggests that no irreversible reactions of the test compounds, or column poisoning, are taking place. However, because of the reproducibility problem and extreme "tailing" encountered with propionic acid, the possibility of irreversible reaction of this test compound with the asphalt was re-examined.Propionic acid was injected repeatedly on the sample asphalt column, using sample sizes 0.1 and 2.0 µ . When 0.1-µ samples were used, the 7, varied within the limits of the experimental error.When large 2.0-µ1 injections were made, the lg s dropped from 122 to 95; however, when a 0.1-µ1 sample was subsequently injected, the previous value of 122 was obtained. These data show no significant "poisoning" by propionic acid. The explanation for the lower values of lg obtained when 2.0 µ of propionic acid were used was given in the previous section. Water Displacement. Water in solute samples in other (9) D. M. Ottenstein, J. Gas Chromatogr., 6,129 (1968).systems (70) has a displacement effect on the solute, thus de-

Ammonia vapor has been irradiated with single pulses of electrons at a very high dose rate (1027 eV g−1 s−1) with a Febetron 705. At this dose rate radical–product reactions are not significant. In pure ammonia, hydrogen, nitrogen, and hydrazine are produced and the yields found at 1027 eV g−1 s−1 are: G(H2) = 3.58 ± 0.08; G(N2) = 1.00 ± 0.05; G(N2H4) = 0.58 ± 0.05. The yields are independent of pressure from 1 to 5 atm and of temperature between 20 and 200 °C. Above 250 °C the yields of all three products increase significantly and this is due to reaction [1] competing with radical–radical reactions.[Formula: see text]A rate constant for this reaction has been determined,[Formula: see text]Product yields have been measured for ammonia–propene mixtures. These yields have allowed determination of the primary radiation yields GNH = 0.74; [Formula: see text]; GH = 4.8; and G(−NH3) = 5.4.