摘要:

Normal subjects were presented simultaneously aligned consonant‐vowel stimuli in three forced‐choice dichotic experiments in which the information content of one signal was changed by (1) varying the intensity, (2) low‐pass filtering, and (3) alterations in signal‐to‐noise ratios. The results of all three experiments were complementary. As signal characteristics were varied to produce a reduction of information to one ear, and thus a decrement in performance, an increment in performance of the unaltered ear was observed. The trade‐off ratios of decrement and increment were such that total performance (summed ear scores) remained virtually constant. Dichotic ear effects (e.g., right ear outperforming left ear) appear to be orthogonal to this phenomenon. These observations indicate that perception of dichotically presented consonant‐vowel depends upon the central additivity of information from two quasi‐independent channels, overall performance being limited by the capacity of the central processor. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.3437390

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

Recent experiments employing an adaptation paradigm have demonstrated the possibility of phonetic feature detectors in speech perception (Eimas and Corbit, 1973). These results could be explained by Adaptation Level Theory (ALT), assuming the reference for categorizing a speech sound is external. In the present experiment, identification functions were obtained for a series of synthetic speech sounds ranging perceptually from /ba/ to /pa/ and a series of tones varying in intensity from 60 to 84 dB SPL. The distribution of occurrences of each stimulus in a series was varied for both tones and speech stimuli. The category boundaries for the tones shifted as a function of the relative number of occurrences of each tone as predicted by ALT. However, the phonetic boundaries for the speech stimuli failed to show the analogous shift. These results suggest that the response criteria for phonetic boundaries may be mediated by an internally generated reference. In contrast, the reference for the nonspeech category boundaries is under external stimulus control.

ISSN:0001-4966    

DOI:10.1121/1.3437403

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

Three tape recorded samples of sentence material having average fundamental frequencies of 119, 139, and 179 Hz were selected from a larger stimulus set [J. F. Brandt, “Effects of Stimulus Bandwidth on Listener Judgments of Vocal Loudness and Effort,” J. Acousl. Soc. Am. 52, 705–707 (1972)]. The speech samples were presented to five normal‐hearing listeners, unfiltered, and high‐pass and low‐pass filtered at 1500 Hz. Pitch matches to the speech samples were made using a filtered ac pulse train of varying repetition rate and energy centered around 2200 Hz. The fundamental frequency of the speech samples was perceived by the listeners in basically the same way that periodicity pitch (nonspeech signals) information is obtained. That is, the fundamental pitch information contained in continuous speech can be easily obtained from temporal (envelope) information in the physical absence of low‐frequency energy. Listeners could also recognize differences between normal‐speaking fundamental frequencies and fundamental frequencies produced at frequencies higher and lower than normal.

ISSN:0001-4966    

DOI:10.1121/1.3437407

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

Flow‐related internal noise generated by a control valve in an air jet‐noise rig or, by analogy, combustors in an engine can become the dominant noise source at low jet velocities or provide a floor for jet noise suppressors. Acoustic data, with and without forward velocity, were obtained with a convergent circular nozzle using a quiet flow system and one dominated by a low‐frequency internal noise source. Forward velocity effects were obtained by installing the test nozzle in a free jet. Farfield noise data, obtained at jet pressure ratios from 1.3 to 1.7 and forward velocities up to 260 ft/sec, are presented in terms of SPL and PWL spectra, directivity, and total power. With a quiet flow system, jet noise is reduced by forward velocity as a function of the product of the sixth power of the relative velocity and the second power of the jet velocity. However, with a dominant low‐frequency core noise source, the portion of the noise spectra dominated by this source was not appreciably affected by forward velocity. The high‐frequency spectral portion of the jet noise was reduced by forward velocity independently of the flow systems used.

ISSN:0001-4966    

DOI:10.1121/1.3437412

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

A technique has been developed for predicting the probability of sonic boom structural damage. This technique utilizes the probability density functions (pdf's) of the sonic boom induced stress and the material strength. Analysis of the data from experiments performed at Oklahoma City, White Sands, and Edwards Air Force Base has shown the stresses produced by sonic booms on windows to have lognormal pdf's. Similarly, analysis of the breaking strength distribution for glass plates has shown it to be log‐normal. From these pdf's a statistical model has been developed for predicting the probability of window breakage as a function of nominal pressure, window size, aircraft flight path direction, and boom duration. Calculations from the model indicate a breakage probability of 1.1 breaks per million panes in good condition boomed at a nominal overpressure of 1 lb/ft2. Results predicted by the model agree well with experimental data at both high and low overpressures. [Work supported by Federal Aviation Administration.]

ISSN:0001-4966    

DOI:10.1121/1.3437418

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

Anatomical studies of the reptilian ear have demonstrated phylogenetic and adaptive modifications at morphological, histological, and cytological levels. Morphologic differences in the cochlear duct appear to form orderly patterns, distinctive to familial levels. Limited but increasing evidence suggests that those differences are accompanied and extended by specialization in the basilar papilla. In turtles, early derivatives of stem reptiles, the organization of that receptor fits the concept of “primitive sensory epithelia” (Wersall and Flock, 1965). Snakes and amphisbaenians, derived from stock leading to lizards, show stages of neuroepithelial specialization, particularly in sustentacular cells. Lizards show additional cytoskeletal specialization of supporting elements; their hair cells frequently exhibit ciliary elongation and specific patterns of polarization, usually combined with tectorial modifications and absence of efferent innervation. In iguanid lizards, and possibly other families, different genera show stages of papillar specialization that correlate with accepted phylogenetic concepts and reported differences in auditory capabilities. Alligators, stemming from stock leading to birds, have unique sensory and sustentacular cells within a receptor clearly related to avian conditions. [Supported by Research Grant NS‐07860, NINDS.]

ISSN:0001-4966    

DOI:10.1121/1.3437421

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

A marked differentiation between the outer and inner hair cells is one of the characteristics of the mammalian cochlea. These two groups of cells are separated by Corti's tunnel, which is presumably filled with Corti's lymph. Communication between Corti's tunnel and the scala tympani is thought to be accomplished by Schuknecht's channel, the presence of which in mammals was confirmed in the present study. It was also confirmed that the endolymphatic spaces of fresh frozen mammalian cochleae are filled with proteinaceous (or fibrillar) material(s), as reported by A. Flock. Mammalian sensory hairs are unique in their arrangement and in the loss of kinocilia as the organ of Corti matures, in contrast to the sensory hairs of other animal classes, which are strikingly similar to the mammalian vestibular sensory hairs. The mammalian outer hair cell sensory hairs are firmly attached to the tectorial membrane, but it is controversial whether the inner hair cell sensory hairs are likewise attached. The physiological significance of this arrangement and the cyto‐archi‐tecture of the mammalian organ of Corti are discussed. In addition, the stria vascularis, the spiral limbus, and Reissner's membrane, which are implicated in the production and/or maintenance of endolymph, are discussed.

ISSN:0001-4966    

DOI:10.1121/1.3437423

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

Sonar fluctuations received intensive study during the hectic days of World WarII, when the causes of fluctuation were identified and some quantitative data were obtained at the frequencies and ranges of current interest. Since then, in the search for mean values of the sonar parameters, fluctuations have tended to be neglected as a subject of serious study. They are the result of the mobile, varying nature of the medium and the objects within it. For example, echoes fluctuate because of the constantly changing heading of a submarine underway; the ambient background fluctuates because of changing ship traffic, wind speed, and biological activity; CW signals fluctuate because of a changing multipath structure of the medium. Examples of these effects, as observed in NOL field work, are presented. Their effect on detection is to improve detection at low mean S/N ratios and to cause lost contacts at high S/N ratios. Quantitatively, this behavior can be expressed by means of ROC curves modified to include fluctuations. However, much more work needs to be done on the second‐order statistics of underwater sound before their magnitude can be predicted and their effects understood.

ISSN:0001-4966    

DOI:10.1121/1.3437431

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

In order to effectively use a ray tracing model it is advisable to determine its sensitivity to small perturbations in the velocity of sound. A model to compute transmission loss based on ray theory and using cubic splines for the sound velocity profile is presented and its sensitivity is examined. The sound velocity profile is perturbed randomly and the mean and standard deviation of the transmission loss is computed.

ISSN:0001-4966    

DOI:10.1121/1.3437432

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP

摘要:

It has been stated that the total modulation distortion produced by a loudspeaker system is inversely related to the efficiency of the system, and that horn‐loaded systems display less of this distortion than the best direct radiators [P. W. Klipsch, “Modulation Distortion in Loudspeakers,” J. Audio Eng. Soc. 17, No. 2 (Apr. 1969)]. This statement runs contrary to modulation theory, which relates modulation distortion to the amplitude or velocity of diaphragm vibration. Measurements were made both on a high‐quality, full‐range horn‐loaded system and on a large, full‐range direct‐radiator system. Each system was driven with the sum of a 41‐Hz and a 350‐Hz tone to evaluate woofer distortion, and with the sum of a 510‐Hz and a 4.4‐kHz tone to evaluate mid‐range distortion. Output levels ranging up to 110 dB SPL were used. The acoustic output of the speakers was fed to a real‐time spectrum analyzer, and total modulation distortion calculated after the method described by Klipsch. Under all conditions measured, the direct radiator produced substantially less distortion. For example, at 110 dB SPL output, its woofer modulation distortion was 3.9% vs 5.8% for the horn system.

ISSN:0001-4966    

DOI:10.1121/1.3437441

出版商:Acoustical Society of America    

年代:1974

数据来源: AIP