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31.
Finneran JJ Schlundt CE Carder DA Ridgway SH 《The Journal of the Acoustical Society of America》2002,112(1):322-328
Auditory filter shapes were estimated in two bottlenose dolphins (Tursiops truncatus) and one white whale (Delphinapterus leucas) using a behavioral response paradigm and notched noise. Masked thresholds were measured at 20 and 30 kHz. Masking noise was centered at the test tone and had a bandwidth of 1.5 times the tone frequency. Half-notch width to center frequency ratios were 0, 0.125, 0.25, 0.375, and 0.5. Noise spectral density levels were 90 and 105 dB re: 1 microPa2/Hz. Filter shapes were approximated using a roex(p,r) function; the parameters p and r were found by fitting the integral of the roex(p,r) function to the measured threshold data. Mean equivalent rectangular bandwidths (ERBs) calculated from the filter shapes were 11.8 and 17.1% of the center frequency at 20 and 30 kHz, respectively, for the dolphins and 9.1 and 15.3% of the center frequency at 20 and 30 kHz, respectively, for the white whale. Filter shapes were broader at 30 kHz and 105 dB re: 1 microPa2/Hz masking noise. The results are in general agreement with previous estimates of ERBs in Tursiops obtained with a behavioral response paradigm. 相似文献
32.
We assessed how listener's judgments of a set of urban sound environments were affected by co-occurring visual settings. In artificial audiovisual environments, subjects rated eight urban sound environments (recordings) when they were associated with five visual settings (four color slides varying in degree of urbanization and a control condition with no slide), along two sound scales (Unpleasant-Pleasant and Stressful-Relaxing). In general, the more urban the visual setting, the more negative the sound ratings. However, this influence depended on the type of sound. It was marked for recordings which did not include human sounds (particularly strong for bird song and weaker for traffic noise), but was absent for all recordings which included human sounds (footsteps and voices). Results are discussed in terms of the degree of matching between visual and sound information, and the degree of implication of the perceiver with these sound environments. 相似文献
33.
Saxon E Luchansky SJ Hang HC Yu C Lee SC Bertozzi CR 《Journal of the American Chemical Society》2002,124(50):14893-14902
The structure of sialic acid on living cells can be modulated by metabolism of unnatural biosynthetic precursors. Here we investigate the conversion of a panel of azide-functionalized mannosamine and glucosamine derivatives into cell-surface sialosides. A key tool in this study is the Staudinger ligation, a highly selective reaction between modified triarylphosphines and azides that produces an amide-linked product. A preliminary study of the mechanism of this reaction, and refined conditions for its in vivo execution, are reported. The reaction provided a means to label the glycoconjugate-bound azidosugars with biochemical probes. Finally, we demonstrate that the cell-surface Staudinger ligation is compatible with hydrazone formation from metabolically introduced ketones. These two strategies provide a means to selectively modify cell-surface glycans with exogenous probes. 相似文献
34.
35.
Carolyn E. M. Morris A. E. Alexander A. G. Parts 《Journal of polymer science. Part A, Polymer chemistry》1966,4(5):985-995
The polymerization of methyl acrylate in water and in dilute, aqueous, soap solutions, initiated by potassium peroxydisulfate, has been investigated, a dilatometric method being used to follow the conversion. It has been shown that small amounts of an anionic soap increase the rate of reaction while a cationic soap has the reverse effect. The change of molecular weight with conversion has also been examined as well as the effect of the exclusion of oxygen from the system. 相似文献
36.
The inhomogeneous master equation obtained in a previous paper (by Van Vliet) is employed to obtain as first-moment equation two quantum mechanical Boltzmann equations (diagonal) for systems of weakly interacting identical particles. The interactions considered are of a binary nature: fermion-fermion or boson-boson. The resulting equations have the same structure as before. The total Boltzmann equation (diagonal and nondiagonal part) is also derived. 相似文献
37.
This paper describes the design of a bilinear time-frequency distribution which is a joint model of temporal and spectral masking. The distribution is used to generate temporally evolving excitation patterns of nonstationary signals and systems and is conceived as a tool for acousticians and engineers for perceptual time-frequency analysis. Distribution time and frequency resolutions are controlled by a separable kernel consisting of a set of low-pass time and frequency smoothing windows. These windows are designed by adapting existing psychoacoustic models of auditory resolution, rather than using mathematical window functions. Cross-term interference and windowing clutter are highly suppressed for the distribution, ensuring resolution accuracy over a dynamic range sufficient to encompass that of the auditory system (in excess of 100 dB). Application to the analysis of a synthetic and two real signals are included to demonstrate the approach. 相似文献
38.
Temporary threshold shift in bottlenose dolphins (Tursiops truncatus) exposed to mid-frequency tones
Finneran JJ Carder DA Schlundt CE Ridgway SH 《The Journal of the Acoustical Society of America》2005,118(4):2696-2705
A behavioral response paradigm was used to measure hearing thresholds in bottlenose dolphins before and after exposure to 3 kHz tones with sound exposure levels (SELs) from 100 to 203 dB re 1 microPa2 s. Experiments were conducted in a relatively quiet pool with ambient noise levels below 55 dB re 1 microPa2/Hz at frequencies above 1 kHz. Experiments 1 and 2 featured 1-s exposures with hearing tested at 4.5 and 3 kHz, respectively. Experiment 3 featured 2-, 4-, and 8-s exposures with hearing tested at 4.5 kHz. For experiment 2, there were no significant differences between control and exposure sessions. For experiments 1 and 3, exposures with SEL=197 dB re 1 microPa2 s and SEL > or = 195 dB re 1 microPa2 s, respectively, resulted in significantly higher TTS4 than control sessions. For experiment 3 at SEL= 195 dB re 1 microPa2 s, the mean TTS4 was 2.8 dB. These data are consistent with prior studies of TTS in dolphins exposed to pure tones and octave band noise and suggest that a SEL of 195 dB re 1 microPa2 s is a reasonable threshold for the onset of TTS in dolphins and white whales exposed to midfrequency tones. 相似文献
39.
40.
Richie C Kewley-Port D Coughlin M 《The Journal of the Acoustical Society of America》2003,114(5):2923-2933
This study examined the effects of mild-to-moderate sensorineural hearing loss on vowel perception abilities of young, hearing-impaired (YHI) adults. Stimuli were presented at a low conversational level with a flat frequency response (approximately 60 dB SPL), and in two gain conditions: (a) high level gain with a flat frequency response (95 dB SPL), and (b) frequency-specific gain shaped according to each listener's hearing loss (designed to simulate the frequency response provided by a linear hearing aid to an input signal of 60 dB SPL). Listeners discriminated changes in the vowels /I e E inverted-v ae/ when F1 or F2 varied, and later categorized the vowels. YHI listeners performed better in the two gain conditions than in the conversational level condition. Performances in the two gain conditions were similar, suggesting that upward spread of masking was not seen at these signal levels for these tasks. Results were compared with those from a group of elderly, hearing-impaired (EHI) listeners, reported in Coughlin, Kewley-Port, and Humes [J. Acoust. Soc. Am. 104, 3597-3607 (1998)]. Comparisons revealed no significant differences between the EHI and YHI groups, suggesting that hearing impairment, not age, is the primary contributor to decreased vowel perception in these listeners. 相似文献