摘要:

R. Bruce Lindsay, reknowned physicist, administrator, educator, and editor, is remembered by his friends and colleagues.

ISSN:0001-4966    

DOI:10.1121/1.392783

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

Meaningful spectrum measurement of musical instruments requires proper specification of the player’s task and proper specification of the instrument itself (in both musical and physical terms). Variations in the room transmission characteristic may be averaged over by moving‐source, moving‐microphone techniques based on current knowledge of the sound field statistics of rooms, and taking into account the angular distribution of the radiated instrumental sound. Detailed discussion of these matters is presented, built around a report on the measurement of two notes on each of six well‐documented clarinets. The lower odd partials have variations of only ±1 dB. For all other partials the variation is ±2 dB arising from all causes. This variation is accounted for about equally by inter‐instrument differences and by player instability. Systematic features of the clarinet spectrum are shown to correlate well with theoretical expectation, and perceptual implications are briefly discussed.

ISSN:0001-4966    

DOI:10.1121/1.392784

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

A detailed modal analysis of several axisymmetrical or fully three‐dimensional Tonpilz transducers is carried out, both with a plane wave approach and with the finite element method. It allows identification and classification of the modes in a broad frequency range (longitudinal modes of the ceramic stack, flexural modes of the head mass, and longitudinal modes of the stress rod) and demonstrates that the motion of the ceramic part of the structure remains essentially of plane wave type. Following this conclusion, a mixed finite element–plane wave method is proposed and described, which gives fairly good results and uses the computational resources efficiently. Moreover, it is likely to be applied to other types of projectors.

ISSN:0001-4966    

DOI:10.1121/1.392785

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The quality of sound pickup in large rooms—such as auditoriums, conference rooms, or classrooms—is impaired by reverberation and interfering noise sources. These degradations can be minimized by a transducer system that discriminates against sound arrivals from all directions except that of the desired source. A two‐dimensional array of microphones can be electronically beam‐steered to accomplish this directivity. This report gives the theory, design, and implementation of a microprocessor system for automatically steering a two‐dimensional microphone array. The signal‐seeking transducer system is implemented as a dual‐beam ‘‘track‐while‐scan’’ array. It utilizes signal properties to distinguish between desired speech sources and interfering noise.

ISSN:0001-4966    

DOI:10.1121/1.392786

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

Computational and measured results of the phase and amplitude distributions of the fields radiated by four circular sources are presented. The limitations of the results are discussed, indicating that meaningful comparison is possible only for planes in and beyond the near‐ and farfield transition regions. The inclusion of an effective radius into the theoretical calculations of a piston in a rigid baffle gives generally good agreement between experiment and theory. The inclusion of the finite size of the receiver produces an additional small improvement. The phase distributions are clearly seen to be a more sensitive index of the field structure than the amplitude distributions commonly used. The value of the work is in suggesting conditions under which one or two amplitude measurements in the field may be used to define effective parameters for an ideal theoretical computation which bears a close resemblance to the actual field radiated by an (imperfect) probe.

ISSN:0001-4966    

DOI:10.1121/1.392787

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

It is a general practice to insert a single electrode pair per muscle for electromyographic recording. The location of electrode insertion influences the character of the signal obtained. The objective of the experiment was to study the relationships between electromyographic signals recorded simultaneously from different locations in an anatomically simple muscle involved in speech production. Signals from three pairs of fine wire electrodes placed high, middle, and low in the palatoglossus muscle of five speakers of American English were amplified, rectified, and integrated. The data were analyzed statistically to determine the patterns of similarity and degree of independence among simultaneous signals from different sites in the muscle for a given speaker. The middle signal was most often the best, and the low signal was most often the poorest representative of the group of signals. The greatest similarity was found between the high and middle signals; next most similar were the middle and low signals. Similarity between signals varied with utterance. In some cases, the relationship between two signals varied over time. This variation may be due to change in interelectrode distance during anisometric contraction or to different motor unit firing patterns.

ISSN:0001-4966    

DOI:10.1121/1.392788

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The problem of glottal source–vocal tract interaction is treated. The effect of the first formant load on the waveform of glottal volume flow is investigated by solving a nonlinear differential equation which describes the variation of pressure drop across the first formant load. The glottal volume flow is calculated under the influence of supraglottal and subglottal formant loads. The estimation of the glottal area function is discussed as an application of the theory developed.

ISSN:0001-4966    

DOI:10.1121/1.392789

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The relative timing of consonant and vowel related movements of the tongue dorsum across variations in stress patterns was examined in two subjects using a computerized pulsed ultrasound system. The patterns observed were similar to those reported by Tulleretal. [J. Exp. Psychol. H.P.P.8, 460–472 (1982)] for interarticulator timing. Correlations between the duration of a ‘‘period,’’ defined as the interval between the onsets of movements associated with adjacent vowels, and the ‘‘latency,’’ defined as the interval between the beginning of the period and the point in the period at which movement associated with the intervocalic consonant begins, were positive and reliable. The source of this correlation pattern was examined and found not to be due to a scaling of an invariant phase relation but rather due to a main effect for stress on the vowel‐to‐vowel articulatory period combined with an artifactual part–whole correlation within each stress level.

ISSN:0001-4966    

DOI:10.1121/1.392790

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated [ph, th, kh], voiceless unaspirated [sp, st, sk], and voiced [b, d, g] stop consonants produced in the context of [i, e, u, o, a]by 8‐ to 9‐year‐old subjects. The results revealed that VOT reliably differentiated voiceless aspirated from voiceless unaspirated and voiced stops, whereasF0 significantly contrasted voiced with voiceless aspirated and unaspirated stops, except for the first glottal period, where voiceless unaspirated stops contrasted with the other two categories. Fundamental frequency consistently differentiated vowel height in alveolar and velar stop consonant environments only. In comparing the results of these children and of adults, it was observed that the acoustic correlates of stop consonant voicing and vowel quality were different not only in absolute values, but also in terms of variability. Further analyses suggested that children were more variable in production due to inconsistency in achieving specific targets. The findings also suggest that, of the acoustic correlates of the voicing feature, the primary distinction of VOT is strongly developed by 8–9 years of age, whereas the secondary distinction ofF0 is still in an emerging state.

ISSN:0001-4966    

DOI:10.1121/1.392791

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

High vowels have a higher intrinsic fundamental frequency (F0) than low vowels. This phenomenon has been verified in several languages. However, most studies of intrinsicF0 of vowels have used words either in isolation or bearing the main phrasal stress in a carrier sentence. As a first step towards an understanding of how the intrinsicF0 of vowels interacts with intonation in running speech, this study examinedF0 of the vowels [i,a,u] in four sentence positions. The four speakers used for this study showed a statistically significant main effect of intrinsicF0 (high vowels had higherF0). Three of the four speakers also showed an interaction between intrinsicF0 and sentence position such that no significantF0 difference was observed in the unaccented, sentence‐final position. The interaction was shown not to be due to vowel neutralization or correlated with changes in the glottal waveform shape, as evidenced by measures of the first formant frequency and spectral slope. Comparison with studies of tone languages and speech of the deaf suggests that both the lack of accent and the lowerF0 caused the reduction in the intrinsicF0 difference.

ISSN:0001-4966    

DOI:10.1121/1.392792

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP