摘要:

The three Lisker—Abramson CV series (ba‐pa, da‐ta, ga‐ka) were computer synthesized at C.I.D. in 1‐msec steps. For each 84‐trial block of a high‐uncertainty, same‐different task (no feedback), one of the three continua was chosen at random. On each trial, the ability of three naive listeners to resolve for differences among VOT pairs ranging from VOT = 10–80 msec, in 10‐msec steps was tested. As expected, there was a local maximum performance for each of the three speech continua, thus satisfying one criterion for categorical perception. A minimum‐uncertainty AX task (with feedback) was run with three highly trained subjects for the ga‐ka continuum. Only one standard VOT was presented in a block of trials. Results were not categorical: the minimum detectable ΔVOT was less than 2 msec at VOT = 10 msec and increased as VOT increased. Our results indicate that trained listeners can utilize subtle stimulus cues in synthetic speech if stimulus uncertainty is minimized. [Supported by a grant from NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2003603

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Brady and Darwin (see Darwin, C.J. The Perception of Speech, in E.C. Carterette, and M.P. Friedman,Handbook of Perception, Academic, New York (in press), Vol. 7, report shifts in the phoneme boundary along a synthetic voicing continuum as a function of the range of stimuli presented within a test. The present study reports comparable shifts along synthetic voicing and place of articulation continua. Implications for the interpretation of adaptation boundary shifts are considered.

ISSN:0001-4966    

DOI:10.1121/1.2003610

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Two discrete levels represented one after another on a graph are normally considered to be connected by a vertical line which has no time value. But the realities of engineering teach us that any vertical line has a time value, no matter how short. If that graph is charting the sound from a single source, we may observe that even extremely dissimilar sounds are connected in a continuum; that they are not items that are arranged, but rather a continuous process of change. Changes may be periodic, transient or random, and they exist at different time scales from “audiotime” (changes in milleseconds) to “conscious time” (changes in seconds). These changes attribute to a sound's “meaning.” The problem for a composer of computer music is how to generate these changes meaningfully.

ISSN:0001-4966    

DOI:10.1121/1.2003614

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Loudness or pitch can be scaled in a space of one dimension. Timbre is multidimensional. The timbre of a musical sound or voice depends upon its time‐varying spectral envelope and periodic fluctuations of amplitude or fundamental frequency. The strengths and weaknesses of scales in describing aspects of tone sensation are contrasted in the light of experiment and theory, both old and new. Multidimensional examples are perceptual spaces of voices and musical structures. Unidimensional examples are the standard scales of loudness and pitch. The adequacy of these is questioned by some recent work done with Norman H. Anderson and based on functional measurement theory. Thus, in one series of experiments, subjects judged loudness averages and differences of noise arrays. The resulting interval scale indicates that loudness is the one‐third power of sound pressure. New work on loudness and pitch scales obtained in bisectioning tasks will be presented.

ISSN:0001-4966    

DOI:10.1121/1.2003619

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A conventional reflection seismic record section displays data only as passing wavefield recorded at points on the earth's surface. In regions of complex geology, this display may bear little resemblance to a cross‐section of subsurface reflectors. Migration is the technique used to transform such a wavefield into a reflectivity display. Different migration methods are derived from either an integral or differential form of the scalar wave equation. In particular, a matched filtering technique involving summation of amplitudes along diffraction hyperbolas is founded on the integral form, and a finite‐difference method pioneered by Jon Claerbout, Stanford University, approximates direct solution of the differential form. After discussing fundamental assumptions required for implementation of the two migration approaches, this paper focuses primarily on comparison migrations of both synthetic data and of marine and land profiles. For good data of modest spatial dip, the two approaches produce similar results. However, the seismic trace spacing (receiver group interval) is found to play different, but fundamental, roles in governing the accuracy and signal‐to‐noise quality of both types of migration.

ISSN:0001-4966    

DOI:10.1121/1.2003620

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The impressive results of applying the synthetic aperture concept in radard has stimulated interest in employing it for mapping the seabed and the seismic structure beneath it. In sonar, several studies have proposed modifications of side scan systems to implement this concept; and in seismics, it is embodied in the operation of migration. These two applications have evolved independently; nevertheless, it appears that each could benefit from the other in solving related problems, particularly with regard to the signal processing. In this presentation we indicate areas of mutual interest in the signal processing of these two applications of the synthetic aperture concept by exploring the similarities and differences from a general array processing perspective.

ISSN:0001-4966    

DOI:10.1121/1.2003622

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Despite the fact that much better seismic data are presently being collected in the deep oceans than was thought possible only two years ago, the present bulk of qualitative and quantitative information about the structures and sediments of the ocean basins resides in the estimated 10 million track‐kilometers of archived single channel seismic data. An enormous amount of invaluable information can be extracted from this resource if the geophysicist/geologist considers the limitations placed on the interpretation of the data by the conditions under which they were collected. The identification of multiples, diffractions, bubble pulses, and velocity effects must be accomplished before the effects of vertical exaggeration can be removed, true dips calculated, features migrated to their true position, and reflector separations more closely approximated. Examples show how each of these data processing steps can be accomplished.

ISSN:0001-4966    

DOI:10.1121/1.2003627

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Using digital techniques, the beamsteering and signal‐generation electronics for a parametric array can be packaged in a smaller volume than the array itself. This leads to a new concept for transducers in which these electronics are considered to be part of the transducer. Such a steerable parametric transducer was designed by APL and proper operation was demonstrated during in‐water tests in June of 1975. The drive waveform for the transducer was generated by pulse width modulating a 21‐kHz square‐wave carrier to produce two primary drive frequencies. The difference freqeuncy (nominally 5 kHz) generated by nonlinearities in the water could be held at a particular frequency or could be readily chirped. Electronic beamsteering in two dimensions was achieved by providing a variable time delay for each element of a 2‐dimensional 61‐element array. The variable delay was achieved by varying the rate at which the modulated carrier was clocked through a matrix of shift registers. The nonlinear beam could be steered to a particular angle or scanned by linear variation of the clock frequency. [Work supported under Navy Contract NO0017‐72‐C‐4401.]11

ISSN:0001-4966    

DOI:10.1121/1.2003630

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

We have set up and are using an apparatus for the measurement of total sound power output of a piezoelectric transducer radiating into water. This apparatus combines the better features of previously used methods which depend on radiation pressure. The input is modulated at a low frequency and the output power is intercepted by an absorbing target which experiences a force at the modulating frequency. The target is mounted on the armature of an electromagnetic microphone provided with an independent coil through which a current at the modulating frequency is adjusted in amplitude and phase, either manually or automatically by feedback, to arrest the motion of the armature. Under these conditions the force depends only on the current, and the apparatus can be calibrated using direct current and dead weights. It is thus absolute. In practice, the carrier frequency is swept over any part of the range 1–80 MHz while a recording of power output versus frequency is made. Examples of curves from normal and defective transducers will be shown. Other applications, as in medical dosimetry will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2003639

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The schlieren observation of broadband acoustic pulses is considered. The optical intensity distributions in both the image and the Fourier transform plane (stop plane) are discussed. Experimental observations are presented for Gaussian‐like pressure transients generated by narrow voltage pulse (∼0.1 μsec) excitation of thick piezoelectric plates. The intensity profiles obtained from these images are compared to calculations we have formulated for Gaussian pressure pulses. These calculations apply in the phase‐grating limit and include optical diffraction effects due to a finite optical beam.

ISSN:0001-4966    

DOI:10.1121/1.2003036

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP