摘要:

Estimates of critical bandwidths in binaural experiments vary considerably across experimental conditions. For masking experiments using signals of varying bandwidths (i.e., spectral integration), and experiments with a frequency‐dependent interaural masker correlation, bandwidth estimates agree with those from monaural experiments. However, if auditory bandwidths are estimated from binaural band‐widening masking experiments, the effective bandwidth is usually a factor of 2 to 3 times larger than monaural estimates. One often ignored detail is that this difference between monaural and binaural estimates decreases with decreasing masker level [Halletal., J. Acoust. Soc. Am.73, 894–898 (1983)]. Using the binaural model described by Breebaartetal., we have simulated the binaural experiments described above. It can be shown that, without any parameter change in the model, basically all relevant conditions can be modeled accurately, including the band‐widening and spectral integration experiments. In agreement with the scheme discussed by Kohlrauschetal., detection in binaural narrow‐band‐noise conditions is improved by analyzing the internal representation in several adjacent filters. It is concluded that the absence of this detection advantage in monaural random‐noise conditions is the primary cause for the so‐called ‘‘wider binaural critical band.’’

ISSN:0001-4966    

DOI:10.1121/1.422908

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The structure‐borne sound characteristics of a commonly found fan installation were examined through measurements and further analyses in the frequency range up to 500 Hz. The focus was to determine the prediction improvements by including the rotational degrees of freedom. Free velocities of the fan were measured in five degrees of freedom (in‐plane rotation or twisting motion were neglected), while fan mobilities were measured and foundation mobilities were predicted in three degrees of freedom: a translational and two rotational, those resulting in bending motion. The two in‐plane translations were considered by transforming their motion to rotations resulting in moment excitations on the foundation. Measurements were also made of the corresponding isolators’ stiffness values. Comparisons are made with power measurements of the complete system. It was found that an unsatisfactory moment excitation resulted in one of the rotational degrees of freedom while employing a twin shaker arrangement when determining the fans’ mobilities. Therefore, a source signal filtering technique was applied to improve the measurement. Comparisons are made with the originally measured mobilities. [This work has been supported by the Swedish Council for Building Research (BFR) through Contract 950192‐8 and the Swedish Research Council for Engineering Sciences (TFR) through Contract 95‐160.]

ISSN:0001-4966    

DOI:10.1121/1.422914

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Optimization techniques to ensure synthesis of stiffened and laminated composite panels subjected to acoustic excitation are presented. The criteria for optimization are established to balance the structure weight and fatigue life. Test spectrum of loading pressure fluctuations is in use, with the parameters of pressure correlation ensuring the greatest response. For stiffened structures, stress spectra and corresponding root‐mean‐square values in points of maximum response are computed by means of special software to draw the special final diagrams that connect nondimensional structure parameters and optimization criteria. These diagrams are then used to select optimal parameters of reinforcement. For composite structures, correlation of the nondimensional parameters representing structure stress level, acoustic load level, dominant frequency of vibration, and panel anisotropy is computed by the same technique. The functions computed are later used to estimate how the criterion for optimization depends on the number of layers, lay‐up sequence, and the directions of fibers. The approach proposed allows aerospace designers to select and motivate their decisions having increased confidence in the development and modifications of these structures.

ISSN:0001-4966    

DOI:10.1121/1.422919

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

To explore the idea that speech motor goals are acoustic targets, upper lip protrusion and tongue blade fronting were examined in the sibilant /∫/ for evidence of motor equivalence in eight speakers of American English. Positive correlations across multiple repetitions of /∫/ (motor equivalence) would occur if the upper lip compensated with more protrusion when the tongue blade was further forward and vice versa. This motor equivalence would serve to maintain an adequate front cavity size for good acoustic separation from /s/ and enhance the acoustic stability of /∫/. It was hypothesized that motor equivalence would be found among less prototypical tokens, as elicited in a ‘‘clear+fast’’ speaking condition. Acoustic spectral analyses indicated excellent acoustic separation between the two sibilants, even in the ‘‘clear+fast’’ condition. There were significant positive correlations of the tongue‐blade and upper lip movements for 28% of all possible cases, with considerable individual variation. When motor equivalence could be compared across the speaking condition, the tokens produced with the motor equivalent pattern were acoustically less prototypical. No occurrences of negative movement correlations were found. One possible source of individual variation may be the use of saturation (quantal) effects, which could also enhance acoustic stability. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.423102

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Ejectives in Athabaskan languages have been investigated phonetically by Lindau (1984), McDonough and Ladefoged (1993), in Navajo, and by Davis and Hargus (1994, 1996) in Babine/Witsuwit’en. In the latter two investigations, three different types of production were found associated with glottal consonants, only one of which showed the classic ejective pattern with a silent period. Examination of samples of Tanana Athabaskan recorded in 1961, 1962, 1974, and the early 1990s found similar variation in samples of this Alaskan Athabaskan language. There appeared, however, to be no examples of ejectives without silent periods in the oldest samples (1961 and 1962). This suggests the hypothesis that the ejective without silent period is an innovation in the last generation of Tanana speakers. Recordings analyzed include a set of standardized word lists recorded by McKennan in 1962 with speakers of Minto, Chena, and Salcha dialects; texts of Teddy Charlie (Minto) recorded by Michael Krauss in 1962; and 3keywords2 recordings of Isabel Charlie (Minto) and Eva Moffit (Salcha) recorded by James Kari and Siri Tuttle in 1991. [This work has been supported by NSF.]

ISSN:0001-4966    

DOI:10.1121/1.422920

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Although vowels can be produced with manyF0 values, high vowels’F0s tend to be higher than low vowels’, a tendency found for every language examined. Nonetheless, this ‘‘intrinsicF0’’ (orIF0) has been called a deliberate ‘‘enhancement’’ of the speech signal, aiding vowel height perception. SinceIF0 remains constant with the number of vowels in a language, this enhancement seems unlikely. The only positive evidence for it is that activity of the cricothyroid (CT) muscle, which primarily raisesF0, is larger for high vowels than for low. The present experiment explores this by having subjects produce vowels at slightly differentF0s, with the differences being similar to theIF0 magnitude for each subject. The first subject (of four planned) showed no vowel height difference in CT; further, an analysis factoring outF0 as a covariate showed that high vowels had higher CT activation. Thus different vowels involve different levels of CT activity for a givenF0; previous findings were likely due not toF0 control but toF0/vowel quality interactions. Even the EMG evidence, then, rendersIF0 an unlikely speech enhancement. Rather,IF0 appears to be an automatic consequence of vowel production. [Supported by NIH Grant DC‐02717.]

ISSN:0001-4966    

DOI:10.1121/1.422930

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

This paper documents the acoustic characteristics of what have been called devoiced vowels in Tokyo Japanese, traditionally attributed to the phonological rule of high vowel devoicing [T. J. Vance, Introduction to Japanese Phonology (1987)]. More recently they have been attributed to articulatory gesture overlap [S‐A. Jun and M. E. Beckman, Paper, Annual Meeting of the LSA (1993)]. Current research by the author indicates both processes are consistent with the data. The vowels which have undergone phonological processing, however, are not simply devoiced; they have undergone a process of obstruentization similar to that found in the Turkish language of Uyghur discussed both pedologically [R. F. Hahn, Spoken Uyghur (1991)] and phonologically [E. M. Kaisse, Language68, 313–332 (1992)]. Specifically, the vowel sites surface as voiceless fricatives at the place of articulation of the preceding voiceless consonant. This is evidenced acoustically by high‐frequency frication in spectrograms and a high number of zero crossings. Additionally, formant frequency information is preserved, as evidenced by formant bars in spectrograms and spectral sections, allowing the perception of the original vowels in the face of heavy loss of vocality.

ISSN:0001-4966    

DOI:10.1121/1.422932

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Categorial discrimination tests (CDTs) with equal opportunities for ‘‘hits’’ and ‘‘false alarms’’ assessed native Japanese and English subjects’ perception of English and Japanese segmental contrasts. The stimuli consisted of vowels and consonants spoken at two rates by five native speakers each of English and Japanese. The listeners chose the odd item out in triads, if there was one, or responded ‘‘none’’ if they heard three physically different tokens of a single vowel or consonant. A’ scores were computed for each contrast. The subjects were ten native English (NE) controls, ten ‘‘experienced’’ bilinguals (Japanese speakers who had spent several years in the United States), and ten ‘‘inexperienced’’ bilinguals (Japanese speakers who had never lived outside Japan, but had studied English in school). Analysis of the CDT results will help determine (1) if the subjects differ in their ability to discriminate consonants and vowels, (2) if perceptual sensitivity to vowel and/or consonant contrasts is affected by the speech rate, and (3) if the experienced bilinguals more closely resemble the NE controls than the inexperienced bilinguals do. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.422937

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Previous research has demonstrated significant improvements in the intelligibility of synthetic speech following listener training [E. Schwabetal., Human Factors27, 395–408 (1985)]. In the present study, the effect of listener training on second‐language speech intelligibility was investigated. Chinese‐accented words and sentences were presented to four groups of native English listeners—one training and one control group for each of two speakers. On word trials, listeners were instructed to select the word presented from two minimal‐pair alternatives; on sentence trials, listeners were instructed to write down what they heard. Listener responses were scored as percent of intended words correctly identified. The two training groups participated in three 1‐h training sessions. Auditory and visual feedback was provided to listeners during the training sessions only. Performance of the training and control groups was compared across pre‐ and posttraining test sessions. Improvement in minimal‐pair word intelligibility following training was found across speakers for the training group, relative to the control group; a similar but smaller improvement in sentence intelligibility was found. Word results will be discussed in terms of improvement in discriminability following training for the twelve phonemic contrasts tested. [Work supported in part by NIH‐NIDCD Grant No. 2R44DC02213.]

ISSN:0001-4966    

DOI:10.1121/1.422938

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The mismatch negativity (MMN) auditory‐evoked potential reflects the detection of minimal stimulus differences at a preattentive level. It has been reported that the MMN reflects acoustic, rather than phonetic processing of speech stimuli. The purpose of the present study was to examine the relationship between discrimination at a neurophysiologic level, as reflected by the MMN, and the behavioral ability of native speakers of American English to discriminate and label pairs of Hindi stop consonants that are contrasted by a place of articulation feature that is not phonemic in English. These pairs were the voiceless unaspirated Hindi stop consonants, dental and retroflex /t/, and the voiced unaspirated Hindi stops, dental and retroflex /d/. The present study addressed two questions: (1) whether the MMN response would be evoked by acoustic differences resulting from differences in place of articulation, even though behavioral discrimination ability was poor; and (2) whether there would be a difference in the presence/absence or other parameters (latency, duration, amplitude, and area) of the MMN response depending on which voicing contrast was presented.

ISSN:0001-4966    

DOI:10.1121/1.422943

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP