摘要:

Calculation of the transient response of piezoelectric elements by analytical means is only possible for a small range of exciting functions for which simple Laplace transforms exist. Calculation tends to be tedious due to the large number of terms which must be evaluated. A method is presented by which the Laplace transformed three‐port model of a piezoelectric element is approximated by a discrete time system by application of thez‐transform. A recurrent time domain solution is developed and this is applied in the manner of a digital filter to a variety of exciting functions. The method has the advantage that the response to any real input can be evaluated and it is thus of considerable use in the testing of piezoelectric elements or the measurement of their physical properties in transient tests. Experimental results are presented which show that the technique is reliable and accurate.

ISSN:0001-4966    

DOI:10.1121/1.390274

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The effects of hydrostatic pressure and pressure cycling on the piezoelectric properties of polyvinylidene fluoride (PVF2) have been experimentally investigated by using an acoustic reciprocity technique. The hydrostatic piezoelectric constants and the relative dielectric constant were measured as a function of pressure and pressure cycling for both voided and nonvoided PVF2samples. The dynamic response of these materials to high‐amplitude pressure pulses having a rise time of 1–3 ms was also determined. The results showed that the microvoid structures in PVF2improve the material’s piezoelectric properties but at the same time increase its pressure dependence and introduce a hysteresis effect with changing hydrostatic pressure. Nonvoided PVF2films were also shown to have a good dynamic response to pressure pulses and, therefore, are promising for applications such as underwater shock sensors.

ISSN:0001-4966    

DOI:10.1121/1.390275

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

This study presents a psychoacoustic analysis of the integration of spectral and temporal cues in the discrimination of simple nonspeech sounds. The experimental task was a same–different discrimination between a standard and a comparison pair of tones. Each pair consists of two 80‐ms, 1500‐Hz tone bursts separated by a 60‐ms interval. The just‐discriminable (d′=2.0) increment in duration Δt, of one of the bursts was measured as a function of increments in the frequency Δf, of the other burst. A trade off between the values of Δtand Δfrequired to perform atd′=2.0 was observed, which suggests that listeners integrate the evidence from the two dimensions. Integration occurred with both sub‐ and supra‐threshold values of Δtor Δf, regardless of the order in which the cues were presented. The performance associated to the integration of cues was found to be determined by the discriminability of Δtplus that of Δf, and thus, it is within the psychophysical limits of auditory processing. To a first approximation the results agreed with the prediction of orthogonal vector summation of evidence stemming from signal detection theory. It is proposed that the ability to integrate spectral and temporal cues is in the repertoire of auditory processing capabilities. This integration does not appear to depend on perceiving sounds as members of phonetic classes.

ISSN:0001-4966    

DOI:10.1121/1.390276

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Masked thresholds for a 1000‐Hz sinusoidal signal were measured as a function of masker level in both forward and simultaneous masking for two types of maskers: a 1000‐Hz sinusoid and a narrowband noise, 60‐Hz wide, centered at 1000 Hz. In forward masking, the noise masker produced much steeper growth‐of‐masking functions than the sinusoid. Presenting a contralateral broadband noise ‘‘cue’’ with the forward masker dramatically reduced the slope of masking for the noise masker but did not influence results for the sinusoidal masker. The noise remained the more effective masker. The amount of masking produced by combinations of equally effective narrowband‐noise and sinusoidal maskers was compared to that produced by each masker individually with and without the contralateral cue. No additional masking beyond that predicted by energy summation was measured for forward masking. Additional masking beyond energy‐sum predictions was measured for analogous conditions in simultaneous masking. Comparisons of results obtained with and without the contralateral cue suggest that signal thresholds in the presence of narrowband‐noise forward maskers can reflect nonperipheral auditory processes.

ISSN:0001-4966    

DOI:10.1121/1.390277

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

An experiment was conducted in order to compare the importance of information from frequency regions remote from the nominal signal frequencies for frequency discrimination and signal detection. In both tasks, signals were presented within the ‘‘notch’’ of band‐reject noise, and different notch widths were employed. The results indicate that information is integrated over a wider range in frequency discrimination than in signal detection. Further, experiments in which a noise floor was present as well as band‐reject noise, indicate that disrupting the information from regions remote from the nominal signal frequencies impairs frequency discrimination even in the absence of any significant impairment of signal detection performance.

ISSN:0001-4966    

DOI:10.1121/1.390278

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Discrimination of envelope frequency was measured as the just noticeable increase in envelope frequency of monotic, 60‐dB two‐tone complexes at geometric center frequencies (CFs) of 500, 1000, 2000, and 4000 Hz. (The envelope frequency is equal to the frequency separation ΔF, between the two components.) At a given CF the jnds were approximately constant up to a critical envelope frequency between 10% and 20% of the CF, roughly equivalent to the critical band, beyond which they increased to a maximum at about 40% of the CF. Below the critical envelope frequency, the jnd increased with CF. Measurements at 40 dB SPL with and without masking of the aural distortion products showed that the influence of aural distortion is minimal. Additional measurements showed that at narrow frequency separations, discrimination was better for monotic two‐tone complexes than for pure tones, three‐tone complexes, and dichotic two‐tone complexes. The results indicate that envelope frequency may serve as a cue for discrimination up to a frequency between 30% and 40% of the CF, although its effectiveness at high enevelope frequencies is severely diminished by the auditory filter. A comparison with other data on envelope frequency discrimination indicates that the jnds’ dependence on the envelope frequency may depend on how the slope of the temporal envelope varies with envelope frequency.

ISSN:0001-4966    

DOI:10.1121/1.390279

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

A model was developed for estimating the pitch of complex sounds that are partially masked by background sound. Our ultimate aim is to obtain a model that can separate two simultaneous sounds on the basis of the harmonic structure of at least one of the sounds. The MDWS model is an extension of the Duifhuis, Willems, and Sluyter pitch meter (DWS) [J. Acoust. Soc. Am.711568–1580 (1982)] which is a practical implementation of Goldstein’s optimum processor theory of pitch perception [J. Acoust. Soc. Am.54, 1496–1516 (1973)]. The main modifications incorporated in MDWS consist of a more faithful modeling of auditory frequency analysis and of an alteration to the criterion used to decide which fundamental best fits a set of resolved components. Effects of the latter modification were investigated in a comparison between model estimates of the pitch of inharmonic complex signals and results obtained for humans. Furthermore, the accuracy of model estimates of the pitch of periodic signals (among which were synthesized vowel sounds), partially masked by noise, was compared with the just noticeable difference of fundamental frequency of these sounds for human observers. The results of these two tests show that the model estimates come close to human perception.

ISSN:0001-4966    

DOI:10.1121/1.390280

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

In order to investigate sound image quality, white and bandlimited noises with various cross‐correlation coefficients are reproduced from two loudspeakers placed in anechoic or echoic chambers. Subjects are asked to make similarity judgments and some subjective evaluations of pairs of the noises. The experimental data are analyzed by Kruskal’s multidimensional scaling (MDS) program. The analysis of the experimental data shows the following: (1) sound image quality depends mostly on the width and the distance of the sound image, (2) the width of the sound image depends on the absolute value of the cross‐correlation coefficient, (3) the distance of the sound image depends on the cross‐correlation coefficient itself, (4) with respect to physical and psychological factors governing sound image quality, there is no fundamental difference between anechoic and echoic chambers.

ISSN:0001-4966    

DOI:10.1121/1.390281

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Intracellular recordings were made from inner hair cells and basilar membrane motion was measured at a similar place, but in different preparations, in the first turn of the guinea pig cochlea. Potential recordings were made using glass microelectrodes and mechanical measurements were made using the Mössbauer technique. Intensity functions of DC receptor potential and basilar membrane velocity in animals with good and poor thresholds are presented. In animals with good thresholds, stimuli at and above the characteristic frequency produce similarly compressive input–output functions for both inner hair cell receptor potentials and basilar membrane motion. However, for frequencies lower than the characteristic frequency, receptor potential input–output functions obtained from animals in good and poor condition show saturation at high stimulus intensities at which basilar membrane motion is linear. This discrepancy is believed to be due to a nonlinear inner hair cell transduction mechanism. We propose that nonlinearity observed in receptor potential input–output functions is a consequence of the simple cascading of a frequency‐dependent nonlinear mechanical input and a frequency‐independent nonlinear transduction process.

ISSN:0001-4966    

DOI:10.1121/1.390282

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The cochlear microphonic, summating potential, and action potential were recorded from all three turns of the gerbil cochlea prior to and following a 1‐h exposure to a high‐intensity pure tone. Results proved that the depression in the cochlear microphonic was greater when recorded from the upper two turns of the cochlea. The losses for the summating potential were not dependent on recording location. Although the cochlear microphonic and to some extent, the negative summating potential, reflected locally generated activity from the hair cells, the positive summating potential appeared to be dependent on distant electrical activity.

ISSN:0001-4966    

DOI:10.1121/1.390257

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP