摘要:

According to the Perceptual Anchor Model of Context Coding [Braidaet al., J. Acoust. Soc. Am.76, 722–731 (1984)], resolution tasks differ in memory coding requirements: basic sensory limitations are measured in fixed discrimination, while context memory limitations can be inferred by comparing fixed discrimination with identification. The theory was applied to two synthetic consonant continua, one varying in voicing (from /ba/ to /pa/), the other in place of articulation (/ba/‐/da/‐/ga/). For both continua, regions of high basic sensitivity were found between the best phonemic exemplars, while optimal context coding occurred near the exemplars. Neither result occurs for an /i/‐/ɪ/‐/ε/ vowel continuum [Goldberget al., J. Acoust. Soc. Am. Suppl. 177, S7 (1985)]. [Work supported by NSF.]

ISSN:0001-4966    

DOI:10.1121/1.2023634

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Ten normal‐hearing subjects listened to a recorded list of 120 whispered consonant‐vowel syllables spoken by a male talker. The consonants were six plosives /b,p,d,t,g,k/, the vowel was /a/. Each syllable was repeated 20 times in random order. The overall consonant identification score was 85.2%. The scores for the voiced consonants were lower than for the voiceless ones, but they were still rather high. The highest average identification score of 96% was obtained for /k/. The average scores were 91%, 88.5%, 83%, 81%, and 71.5% for /t/, /d/, /p/, /b/, and /g/, respectively. A pairwise comparison showed that the difference between /k/ and /g/ scores was significant. With respect to place, alveolars and bilabials had the highest and the lowest scores, respectively. Whispered /b,d,g/ were more often confused with their cognates than vice versa; cognate errors were more numerous than place errors. These results indicate that the voicing contrast is indeed useful for distinguishing voiced and voiceless plosives, however that there are other cues which allow the discrimination between voiced and voiceless consonants if the voicing contrast is absent.

ISSN:0001-4966    

DOI:10.1121/1.2023639

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Across studies when listeners perceive a syllable to have a fricative‐stop initial cluster, they report only one P center. Further, the locations of such P centers shift in a one‐to‐one millisecond manner with changes in pre‐vocalic acoustic durations. We also know there is a lower limit on the duration of silence which allows such clusters to be perceived. In this study we ask about the upper limit on intra‐syllabic silence and we ask if the number and location of P centers can be used to assess listeners' sensitivity to the segmental coherence of syllables. Using natural tokens of [s], [trip]and [strip] by two talkers, the silent interval was varied from (a) isochronous alternation to (b) overlap of [s]and [trip]. Listeners judged the number of events and the location of P centers. For (a) they perceive two separate events, each with a P center. For (b) they perceive two simultaneous events with one P center. When listeners report one event with one P center, they show sensitivity to the naturally produced silent intervals. [Work supported by Alvey.]

ISSN:0001-4966    

DOI:10.1121/1.2023644

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Systems of precisely spaced bubbles, balloons, or air‐filled thin shells in water, in full spaces, or near elastic boundaries, insonified at frequencies close to the fundamental resonance value ω0(“bubble frequency”) and interactingviamultiple scatter may develop true resonant modes or superresonances (SRs). Under SR conditions the pressure amplification relative to the incident field will be of order (kRa)−2, as opposed to (kRa)−1for single scatter at ω0,kRbeing the wavenumber in water andathe scatterer radius. For simple configurations this leads to theoretical SR amplifications between 103and 5 × 103. It is shown here that, in order to observe the SR effect, spacings and volumes must be controlled to12or better. Typical pair spacings are of order13 λacoustor (roughly) multiples thereof. When a bubble/balloon pair is near a thin plate the basic spacing is about one flexure‐wave wavelength and SR amplification becomes very sensitive to the direction of flexure mode arrivals, tending to vanish entirely for angles intermediate between broadside and endfire incidence. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2023650

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Acoustic backscattering from the sea surface at grazing angles in the region of 5 deg is affected by shadowing. Under these conditions the equations presented by Basset al.[IEEE Trans. Antennas Propag.AP‐16(5) (Sept. 1968)] may be combined to form a single equation. The agreement between experimental data near 1 kHz and the unified equation is good. The frequency shift of the backscattered acoustic energy is dependent on wave height and period through the horizontal orbital particle velocity. The frequency spread of backscattered energy is still dependent on the same particle velocity but is diminished because the wave troughs are preferentially insonified. The experimentally determined values of backscattering strength compare favorably with other reported low‐frequency, low grazing angle data.

ISSN:0001-4966    

DOI:10.1121/1.2023654

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP