摘要:

An objective study of the steady‐state interaural time difference (ITD) was performed on a manikin comprised of a head and torso. Data were taken for both a bare and clothed torso. The measured ITD’s correspond reasonably accurately at the low and the high frequencies to the computed theoretical values for a rigid sphere of an effective radiusa. The theoretical ratio of the low‐frequency (<500 Hz) ITD to the high‐frequency (≳2000 Hz) ITD is 3/2. The measured ITD is a minimum between 1.4 and 1.6 kHz for angles of incidence, ϑinc, of sound between 15° and 60°. At both the low and the high frequencies the data can be expressed by universal curves when the ITD is normalized by (a/c0)  sinϑinc, wherec0is the speed of sound in air and ϑincis the angle of incidence. Both the steady‐state ITD and the interaural sound‐pressure‐level difference (ILD) show differences between measurements made with the bare torso and those with a clothed torso. These objectives results support the subjective measurements of past experiments, which showed that in man there was no localization improvement below approximately 500 Hz, poor localization between 1000 and 2000 Hz, and a change in the localization cue around 1400 Hz from ITD to ILD.

ISSN:0001-4966    

DOI:10.1121/1.381498

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Investigation of the temporal integration of the acoustic reflex may be complicated by the operating characteristics of the instrumentation used to record the reflex. Several experiments were conducted to determine the operating characteristics of two impedance measuring systems (Madsen, model Z0−70 and Zwislocki Bridge (Grason Stadler, model 3), and to measure selected characteristics of the acoustic reflex, including (1) ’’threshold’’, (2) reflex intensity‐growth functions, and (3) temporal integration functions at ’’threshold’’ for several stimulus frequencies. Results indicate (1) a smaller impedance change may be identified with a Madsen Z0−70 due primarily to the higher S/N (signal‐to‐noise) ratio in that instrument; (2) differences in temporal integration functions obtained between the two instruments were partially accounted for by differences in the operating characteristics of the two measuring systems; (3) the slope of the growth‐intensity function decreases as signal duration decreases; and (4) the slope of the temporal integration function increases as the frequency of the eliciting stimulus increases.

ISSN:0001-4966    

DOI:10.1121/1.381499

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Listeners were presented with stimuli from a nine syllable [?a]–[da]continuum (constructed using a natural speech [?a]) in which syllables differed in the duration of frication from 52 to 8 msec. In each experimental session, an initial identification test was conducted to determine the category boundary. This base‐line test was followed by one of three adaptation tests in which subjects were presented with repeated syllables. The adapting stimuli consisted of (a) a single [?a]adaptor with 52 msec of frication, (b) a single [?a] adaptor with 32 msec of frication, (c) a ’’variable’’ adapting sequence that included the first six members of the test series and had a mean frication duration of 37 msec. The variable adapting sequence produced an adaptation effect equal in magnitude to the effect produced by the single adaptor with 32 msec of frication. The adapting syllable containing 52 msec of frication produced a significantly larger effect. The results demonstrate that (a) selective adaptation of speech did not require presentation of a constant adapting syllable and (b) the amount of adaptation depends upon the mean duration of frication contained in the adapting material at least up to 52 msec. A second experiment was performed to determine whether adaptation along a [?a]–[da] continuum was linearly dependent upon friction duration at values beyond 52 msec by comparing adaption produced by [?i], [?i], and [di]adaptors, containing friction duration of 120, 60, and 12 msec, respectively. The results showed that [?i] and [?i]produced highly similar adaptation effects on a [?a]–[da]series. The results suggest that an analyzer underlying perception of [?] is neither linearly nor symmetrically tuned to a particular range of friction duration.

ISSN:0001-4966    

DOI:10.1121/1.381479

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The purpose of this experiment was to study both the timing and positional properties of articulatory movements in VCV utterances. Conventional cinefluorographic techniques were used to track the movements of the upper lip, lower lip, jaw, tongue tip, and tongue body of two speakers who read randomized lists of VCV utterances containing the vowels /i,a,u/ and the consonants /p,t,k/, in all possible combinations. Results showed that the timing of articulatory movements in a VCV sequence are constrained by the intervocalic consonant, even if the gesture for the consonant is not a contradictory one. Anticipatory movements toward the second vowel always begin during the closure period of the intervocalic consonant. The appearance of carry over coarticulation effects depends on the phonetic identity of the particular segment or degree of involvement of the articulator. Carry over effects, like anticipatory effects, did not extend beyond an immediately adjacent segment. These findings suggest that the rules governing the segmental input to a speech string might be simpler than present models suggest.

ISSN:0001-4966    

DOI:10.1121/1.381480

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A vocoder‐type speech analyzer interfaced to the tactile display of an Optacon was used to investigate how subjects learned, over a six‐week period, to identify the vibrotactile patterns of different speech signals. Closed sets of four vowel durations, three different vowels, and four spondee words constituted the test material. Learning to identify vibrotactile patterns required many hours of training. Subjects in this study showed significant improvement in the identification of all three types of speech signals, especially the vowel durations and spondee words. Tests for transfer at the end of training showed that shifting the locus of stimulation did not result in decrement in performance.

ISSN:0001-4966    

DOI:10.1121/1.381481

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The reactions of babies to aircraft noise were studied by means of electroplethysmography (PLG) and electroencephalography (EEG). It was found that the babies whose mothers had moved to the area around the Osaka International Airport before conception (group I) or during the first five months of pregnancy (group II) showed little or no reaction on PLG and on EEG to aircraft noise. In contrast, babies whose mothers had moved closed to the airport during the second half of the pregnancy or after birth (group III or IV) and the babies whose mothers lived in a quiet living area (group V) reacted to the same auditory stimuli. The babies in groups I and II showed differential responses depending on whether the auditory stimuli were aircraft noise or music. Abnormal PLG and EEG were observed in the majority of babies living in an area where noise levels were over 95 dBA. This suggests that the deep sleep of the babies living in such an area was disturbed.

ISSN:0001-4966    

DOI:10.1121/1.381482

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The flow‐noise response of two types of gradient hydrophones is investigated by comparing models. Several effects are given detailed investigation, such as differentiating between noise conducted directly from the flow and noise caused by case acceleration. Models are used to predict the operational effects of several types of flow screens.

ISSN:0001-4966    

DOI:10.1121/1.381484

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The dimensionless ratios governing sound propagation in acoustic boundary layers and capillaries, indicate that the specific acoustic impedance of Rayleigh solids can be made invariant under scaling, as required for model experiments involving sound reflection by, or diffraction over, absorptive boundaries. Specifically, if macroscopic dimensionsL, such as the acoustic wavelength or the thickness of the porous layer are scaled down toL/sin the model experiment, the capillary diameter and spacing must be scaled down by a factor of onlys1/2. More generally, a correct model of fibrous layers requires that intersticial dimensions be scaled ass1/2, the layer thickness ass, and that the porosity remain unchanged, i.e., that the number of interstices per unit area be scaled up by a factors.

ISSN:0001-4966    

DOI:10.1121/1.381485

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

In a recent paper, the free‐wave and eigenmode models of the sound field in a reverberation chamber were compared, and evidence was presented to support the thesis that the two models were consistent. Here a further piece of this evidence is given. We consider the spatial variance of the mean‐square pressure in a reverberant sound field of one frequency which has a mean value of unity. This variance, when calculated from the free‐wave model is known to have the value of unity. It is also know that, for one oblique rectangular mode, the corresponding value of the variance is 2.375. It is shown here that forNsuch modes, whose frequencies coincide but whose phases are uniformly distributed, the variance approaches 1 asNapproaches ∞.

ISSN:0001-4966    

DOI:10.1121/1.381487

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A computer simulation method, based on the ray theory of acoustics, has been developed for predicting reverberation decay rates in an architectural enclosure. Comparison of results to solutions of the Eyring equation and to a limited amount of experimental data are very favorable. The method can be extended to complex structures and provides useful results with limited effort.

ISSN:0001-4966    

DOI:10.1121/1.381488

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP