摘要:

A new approach to undersea ambient noise field horizontal directionality estimation from towed line array data is presented. This new technique includes the effects of the three‐dimensional array response and the noise field vertical arrival structure during the estimation process. It is sufficiently general to include the angle of array tilt from the horizontal and does not require noise field stationarity as do most previous methods. The vertical dimension is included in the estimation process through a transformation of the noise field from a spherical coordinate system to a conical coordinate system of the array with an arbitrary tilt angle. The three‐dimensional pseudostationary noise field estimate ? (ϑ,φ) which results is then integrated over the vertical (φ) to obtain the horizontal directionality estimate ? (ϑ). The results indicate significant improvement in ? (ϑ) when the array tilt and noise vertical arrival structure are accounted for.

ISSN:0001-4966    

DOI:10.1121/1.384181

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Electrical activity of single neurons in the spiral ganglion of the guinea pig cochlea was correlated with receptor hair cell damage produced by local mechanical lesions of the organ of Corti. Damage to or loss of hair cells was assessed using scanning electronmicroscopy. Principal finds were (1) neurons emanating from damaged regions showed changes in their tuning curves such as loss of sensitivity, broadening of tuning curves; (2) in some cases, the loss of sharp tuning tip resulted in an apparent shift of the tuning curve to lower frequencies; and (3) apparently pure outer hair cell lesions, of limited spatial extent, could result in the same effects as mixed inner and outer hair cell lesions.

ISSN:0001-4966    

DOI:10.1121/1.384182

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The effects of signal uncertainty on detection performance were measured using a new procedure that allows precise specification of the initial temporal uncertainty. Five different models of the detection process, two assuming a continuous representation of the sensory input and three assuming a discrete representation, were compared with the obtained data. The effects of varying signal uncertainty (the number of potential signal intervals was one, five, or ten) had little effect on detection performance. The one‐parameter form of the choice model can be rejected without hesitation. The continuous Gaussian model and the symmetric two‐state model are significantly different from the data. The high threshold and sophisticated two‐state models provide accurate descriptions of the data that cannot be rejected on statistical grounds.

ISSN:0001-4966    

DOI:10.1121/1.384183

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Pitch phenomena related to the periodic interruption rate of white noise have traditionally been regarded as evidence for time domain pitch processing in the auditory system since spectra of these signals are flat. Short‐term spectra, however, contain information about the interruption rate. Melodic interval identification experiments were performed with sounds comprising low‐pass filtered noise modulated by either a sine wave, a square wave, or a periodic narrow pulse wave. Melodic intervals were generated by varying the modulation frequencyfmwhile the low‐pass cutoff frequencyfcoof the noise was an experimental variable. The correct identification score shows a particular dependence on the ratiofco/fmfor each type of modulation signal. Shapes and relative positions of performance functions are compared with predictions derived from an energy detector (time domain) model and a short‐term power spectrum correlation (frequency domain) model, and are found to support the former more strongly than the latter. There is some evidence, however, for the existence of both types of processing in the auditory system.

ISSN:0001-4966    

DOI:10.1121/1.384184

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Four experiments employed a listening for mispronunciations task to determine how listeners perceive an ordered series of words from a continuous, phonetically ambiguous stimulus. In experiments 1, 2, and 3, listeners’ reaction times to detect mispronunciations were obtained in phonological sequences that could be perceived as either one or two words (e.g., ’’cargo’’ or ’’car go’’ mispronounced ’’carko’’). In experiment 1, segmentation of the acoustic signal as one or two words was guided by the theme of a short story. For example, the sentence ’’They saw the carko on the ferry’’ was spliced into two stories—one about a shipment of cargo, and one about a car about to go on a ferryboat. The results showed significantly faster reaction times—by about 300 ms—when the mispronunciation was perceived as occurring in the second syllable of a word. In experiment 2, alternate segmentations of the same acoustic signal were constrained by the grammatical nature of the first few words in a sentence. Subjects were presented with sentences such as ’’The doctor said that nosetrops will help the cold’’ or ’’The doctor said he knows trops will help the cold.’’ By means of tape splicing, the final portions of the two sentences in each pair were acoustically identical. Reaction times were again found to be faster—by about 150 ms—when the mispronunciation was perceived as occuring in the second or third syllable of a word, rather than at the beginning of a word. Experiment 3 replicated these results using naturally recorded sentences having normal prosody. The results of experiments 1–3 demonstrated that prior context determines how syllables are recognized as words and that a mispronounced second syllable is detected faster than a mispronounced word‐initial syllable. It was argued that mispronunciations are detected more quickly in second syllables because the intended word has been accessed from its first syllable. This hypothesis was further supported in experiment 4. When subjects read each sentence before hearing it, so that all syllables were equally (and perfectly) predictable, mispronunciations were detected equally fast in first and second syllables.

ISSN:0001-4966    

DOI:10.1121/1.384185

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Most theoretical accounts of the identification of stop consonant place of articulation have focused on how bursts and formant transitions conspire to signal place in CV syllables. In the present series of experiments we have examined the identification of place in VCV syllables and have found that not only do the burst and opening transitions affect the judgement of place, but so also do the closing transitions and the duration of the closure interval. This outcome is consistent with the outcomes of many other experiments in showing that there are multiple acoustic events which bear on the identification of a given phone and that those acoustic events are distributed over time. Theoretical accounts of place identification based on data of this kind may prove more viable than theories based on data from the identification of place in the absolute, syllable‐initial position.

ISSN:0001-4966    

DOI:10.1121/1.384186

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Multidimensional scaling analyses of three types of English consonant confusions are reported: consonant substitutions in spontaneous speech errors, CV perceptual confusions, and VC perceptual confusions. Two data sets of each type are analyzed to assess reliability. Three reliable dimensions emerge in all data sets, corresponding to voicing, stop/fricative, and place of articulation. Representation of consonants in terms of categorical phonological features exhaustively describes what is common to the configurations of different data types, even though there is reliable detail within each data type that is not captured by categorical features. Such features can be viewed as groupings of speech sounds common to various perception and production processes.

ISSN:0001-4966    

DOI:10.1121/1.384079

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Five listeners rapidly repeated (’’shadowed’’) a random presentation of the vowel–consonant–vowels (VCV’s) /aba, apa, ama, aka, aga/. Initial vowel duration was varied to eliminate it as a temporal cue to the occurrence of the consonant. These shadowing, choice reaction times (RT’s) were compared to simple RT’s obtained when listeners always produced /aba/ or /ba/ to the same syllables. Both /aba/ and shadowing reactions were extremely fast (170 to 240 ms). Latency differences between the two tasks were attributable to differences in the point at which cues sufficient for responding were present. These results suggest that speech‐perception decisions in shadowing are directly available to, and are perhaps made contemporaneously with, the execution of the speech response. The simple /ba/ responses were observed to occur at a point comparable to the consonantal release seen for the simple /aba/ responses. This result suggests that the motor organization required for a /ba/ response includes an implicit time interval appropriate for a consonantal closure.

ISSN:0001-4966    

DOI:10.1121/1.384187

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Based upon a generalized theory of an analytic model of a practical acoustic radar (echosonde) antenna [S. A. Adekola, J. Acoust. Soc. Am. 60, 230–239 (1976)] whose potential has been exploited to measure atmospheric turbulent velocity fields and temperature fluctuations, we present an analysis of the Fresnel zone and diffraction fields near the boresight of a typical antenna. Invoking the Fresnel zone approximation and employing a tapered parabolic source excitation, the Fresnel zone field at the antenna boresight is evaluated in closed forms in terms of a highly convergent Lommel series function of the form Ω0m(ν,n) that is expedient for practical computations. A generalized diffraction integral equation at the boresight region, which can be used for both circularly symmetric and asymmetric echosonde apertures, is formulated whereby the existing integral, previously derived in the reference above, is split into a sum of zeroth‐order Hankel and Lommel transforms that describe the field in the two principal planes of the aperture. The results clearly demonstrate that circular symmetry still leads to zeroth‐order Hankel transform, while antisymmetry produces an additional Lommel transform. Analytical examples presented include closed form pattern evaluations for some commonly used source excitations, in terms of tabulated Anger–Weber and Struve functions, while illustrative numerical pattern characteristics discussed comprise beam patterns arising from Hamming—cos2on a pedestal—and doublet‐source distributions. A realization of the echosonde antenna described by the integral equations is discussed. Raw, experimentally measured, beam patterns in the acoustic frequency band 1750–3000 Hz are redrafted, statistically averaged, and presented, using standard error bars. We also discuss a facsimile recording that describes the measurements of turbulence components in the lower marine boundary layer, using an echosonde antenna. An attempt is made towards a rigorous treatment of the echosonde synthesis, based on the synthesis integral equations deduced from the results of the diffraction fields.

ISSN:0001-4966    

DOI:10.1121/1.384135

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Piezoelectric microphones are described which utilize a rigidly supported, curved polyvinylidene fluoride membrane. The microphones can be designed with a resonance frequency of about 5 kHz and a sensitivity of −55 to −60 dBV per N/m2. The harmonic distortion is typically below 1% for sound‐pressure levels up to 100 dB. Advantages of these microphone structures are the well‐defined geometry of the membrane, good mechanical and thermal stability, and the possibility of varying the membrane tension and introducing damping by the membrane support.

ISSN:0001-4966    

DOI:10.1121/1.384136

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP