The head-related transfer function ͑HRTF͒ varies with range as well as with azimuth and elevation. To better understand its close-range behavior, a theoretical and experimental investigation of the HRTF for an ideal rigid sphere was performed. An algorithm was developed for computing the variation in sound pressure at the surface of the sphere as a function of direction and range to the sound source. The impulse response was also measured experimentally. The results may be summarized as follows. First, the experimental measurements were in close agreement with the theoretical solution. Second, the variation of low-frequency interaural level difference with range is significant for ranges smaller than about five times the sphere radius. Third, the impulse response reveals the source of the ripples observed in the magnitude response, and provides direct evidence that the interaural time difference is not a strong function of range. Fourth, the time delay is well approximated by well-known ray-tracing formula due to Woodworth and Schlosberg. Finally, except for this time delay, the HRTF for the ideal sphere appears to be minimum-phase, permitting exact recovery of the impulse response from the magnitude response in the frequency domain. a radius of the sphere ͑m͒ c ambient speed of sound ͑m/s͒ f frequency ͑Hz͒ h head-related impulse response h m mth-order spherical Hankel function h m Ј the derivative of h m with respect to its argument Hhead-related transfer function relative to free field H head-related transfer function relative to source i ͱϪ1 j m mth-order spherical Bessel function k acoustic wave number ͑/m͒ n m mth-order spherical Neumann function p f f free-field pressure at the center of the sphere ͑kg/m 2 ) p s pressure on the surface of the sphere ͑kg/m 2 ) p pressure at a small sphere surrounding the source ͑kg/m 2 ) P m Legendre polynomial of degree m Q m mth-order modified spherical Hankel function r distance from the center of the sphere to the source ͑m͒ r radius of a small sphere surrounding the source S magnitude of flow from an ideal point source ͑m 3 /s͒ t time ͑s͒ ⌬t time between arrival at observation point and sphere center ͑s͒ ⌬ normalized ⌬t angle of incidence ͑rad͒ 0 angle for tangent incidence ͑rad͒ wavelength ͑m͒ normalized frequency normalized distance to the source 0 density of air ͑kg/m 3 ) normalized time radian frequency ͑rad/s͒

The effectiveness of a high variability identification training procedure to improve native Japanese identification and production of the American English (AE) mid and low vowels /ae/, /A/, /2/, /O/, /Ç/ was investigated. Vowel identification and production performance for two groups of Japanese participants was measured before and after a 6-week identification training period. Recordings were made of both group's pre-/posttraining vowel productions of the five vowels, which were evaluated by a group of native AE listeners using a five-alternative, forced-choice identification task and by an acoustic analysis of the vowel productions. The overall results confirmed that the identification performance of the experimental (trained) participants improved after identification training with feedback and that the training also had a positive effect on their production of the target AE vowels. When learning a second or foreign language (L2), adults typically have difficulty mastering certain phonemic contrasts in the target language (Best, 1995;MacKain, Best, & Strange, 1981). As language-specific perceivers, adults' perception of speech is attuned to contrastive elements that serve to distinguish native phones during first or native language (L1) acquisition. It can be a challenge for listeners to accurately distinguish between sounds in the L2, or between L1 and

This study examines the auditory attribute that describes the perceived amount of reverberation, known as "reverberance." Listening experiments were performed using two signals commonly heard in auditoria: excerpts of orchestral music and western classical singing. Listeners adjusted the decay rate of room impulse responses prior to convolution with these signals, so as to match the reverberance of each stimulus to that of a reference stimulus. The analysis examines the hypothesis that reverberance is related to the loudness decay rate of the underlying room impulse response. This hypothesis is tested using computational models of time varying or dynamic loudness, from which parameters analogous to conventional reverberation parameters (early decay time and reverberation time) are derived. The results show that listening level significantly affects reverberance, and that the loudness-based parameters outperform related conventional parameters. Results support the proposed relationship between reverberance and the computationally predicted loudness decay function of sound in rooms.

High dynamic range (HDR) photography and physically based rendering produce images with full range of luminance data. The problem of mapping real world luminance into the limited luminance range of display devices has been addressed in the last decade through the development of many different tone mapping algorithms (see [Devlin et al. 2002] for a recent survey). Clearly, a sound methodology for comparing existing algorithms is needed to understand their strengths and weaknesses; this work takes a first exploratory step towards achieving this goal. We performed a series of psychophysical experiments in which human subjects assessed their perceptions associated with a set of 24 images, constructed by submitting four different scenes (both synthetic and photographic) to six popular tone mapping operators: Photographic Tone Reproduction (Reinhard et al. the human contrast sensitivity option was switched off). In this initial attempt, we chose an exploratory rather than confirmatory approach in which subjects first made global judgments regarding how perceptually similar or dissimilar the images were, without specifying the ways in which they might differ from one another. Global dissimilarity judgments were made for all pairwise comparisons of the six tone mapping operators separately for each of the four scenes by each of 11 subjects, and these data were submitted to INdividual Differences SCALing (INDSCAL) analysis. The primary INDSCAL result of interest is a derived Stimulus Space in which each stimulus is assigned coordinates on the dimensions describing the perceptual differences between the stimuli (see [Borg and Groenen 1997] for background on this analysis method). The spatial configuration of the six tone mappers on the two most salient dimensions is shown in Figure 1.In order to aid in the interpretation of the INDSCAL results, psychophysical scale values were obtained for all stimuli with respect to three perceptual attributes: apparent image contrast, apparent level of detail (visibility of scene features), and apparent naturalness (the degree to which the image resembled a realistic scene). Multiple regression analyses revealed that the first, most salient perceptual dimension describing the differences between stimuli was associated linearly with apparent level of detail (r = .85), and the second INDSCAL-derived dimension was most highly associated with apparent naturalness (r = .67). A more complex relationship was found for apparent contrast, the fit regression equation having significant quadratic components on both dimensions of the INDSCALderived Stimulus Space.In order to determine the relationship between these dimensions and subjective preferences for tone mapper outputs, pairwise preference choices were made for all stimuli, and the resulting preference rankings were submitted to PREFerence MAPping (PREFMAP) analysis. This analysis identified an "ideal" preference point in the INDSCAL-derived Stimulus Space, the location of which suggested that the best tone mapping operator should produce ima...

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