Effect Of Timing Errors Research Articles

The effect of timing errors on the intelligibility of deaf children's speech

At the 93rd meeting of the Acoustical Society of America, we presented a preliminary report on a technique to correct deviant timing errors in deaf children's speech by computer processing of recorded speech samples. Timing modifications were accomplished by direct manipulation of the waveform in which whole pitch periods were deleted from steady‐state portions of speech segments, leaving all other aspects of the speech unchanged. The following six‐stage approximation procedure was used to correct the deviant timing patterns: (1) original, unaltered utterance, (2) correction of pauses only, (3) correction of relative timing (stressed/unstressed ratio), (4) correction of absolute syllable duration, (5) correction of relative timing and pauses, and (6) correction of absolute syllable duration and pauses. This report will present preliminary data on the changes in intelligibility that occurred as a result of the systematic timing corrections Intelligibility measures were obtained by playing the original sentences and the computer‐modified versions to persons not familiar with the speech of the deaf. The measure of intelligibility was the proportion of words correctly understood by the listeners. The data showed that, on the average, intelligibility improved slightly when relative timing errors only were corrected. A decrease in intelligibility was observed for the other forms of timing modification. There were marked individual differences and the correction of deviant timing patterns was relatively more important for improving the intelligibility of some children's speech than others. [Research supported by PHS Grant NS 09252.]

The effect of timing errors on the intelligibility of deaf children’s speech

The purpose of this study was to quantify the effect of timing errors on the intelligibility of deaf children's speech. Deviant timing patterns were corrected in the recorded speech samples of six deaf children using digital speech processing techniques. The speech waveform was modified to correct timing errors only, leaving all other aspects of the speech unchanged. The following six-stage approximation procedure was used to correct the deviant timing patterns: (1) original, unaltered utterances, (2) correction of pauses only, (3) correction of relative timing, (4) correction of absolute syllable duration, (5) correction of relative timing and pauses, and (6) correction of absolute syllable duration and pauses. Measures of speech intelligibility were obtained for the original and the computer-modified utterances. On the average, the highest intelligibility score was obtained when relative timing errors only were corrected. The correction of this type of error improved the intelligibility of both stressed and unstressed words within a phrase. Improvements in word intelligibility, which occurred when relative timing was corrected, appeared to be closely related to the number of phonemic errors present within a word. The second highest intelligibility score was obtained for the original, unaltered sentences. On the average, the intelligibility scores obtained for the other four forms of timing modification were poorer than those obtained for the original sentences. Thus, the data show that intelligibility improved, on the average, when only one type of error, relative timing, was corrected.

DIRECT AND INVERSE PROBLEMS RELATING REFLECTION COEFFICIENTS AND REFLECTION RESPONSE FOR HORIZONTALLY LAYERED MEDIA

If a plane wave is normally incident on the boundary of a horizontally layered medium, the reflection and transmission responses can be found in terms of the reflection coefficients at the interfaces of the medium. Recursion formulas for finding these responses have been given by various authors: Goupillaud (1961), Sherwood (1962), Kunetz and d’Erceville (1962), Sherwood and Trorey (1965), and Claerbout (1968). This paper gives explicit solutions of the recursion formulas for the numerator and denominator of the reflection and transmission operators. The solutions are expressed as polynomials in the variable z of the z-transform, with coefficients given as explicit sums of products of reflection coefficients. These formulas are equivalent to those given by Goupillaud. We also give the operator which removes all effects of any given set of layers at the top, the operator being equivalent to one given by Goupillaud. The inverse problem of finding the reflection coefficients from a reflection record or transmission record has been solved in two different, equivalent forms by Kunetz and d’Erceville and Claerbout. This paper gives further results derived along the lines of Claerbout’s paper. Since the solutions are developed for the noise‐free case, the effects of timing errors, scaling errors, and random noise on the reflection coefficient series computation are investigated. Examples are given which show the zones of stabilities. The Appendix gives the general form of the energy conservation equation in elastic wave propagation in strict analogy with the Poynting formulation for electromagnetic wave propagation. The main body of the paper includes a proof that Claerbout’s polynomial identity is an energy conservation equation for the case when no free surface is present.

Characteristics of a wake-vortex tracking system based on acoustic refractive scattering

The theory of acoustic-ray bending by aircraft-generated vortices is developed in a form convenient for application to a practical vortex tracking system. The maximum scattering angle ϑm is proportional to the vortex circulation divided by the average core radius. Since the circulation for commercial jet transports is roughly proportional to the wingspan, the value of ϑm depends little on aircraft size but strongly on the ratio of the core size to the wingspan. For landing aircraft ϑm varies from 0.5 to 1.4 rad depending upon the engine placement. A variety of vortex core models are considered which lead to values of ϑm between 0.2 and 0.9 rad. The capabilities of a pulsed acoustic vortex tracking system depend strongly upon ϑm and therefore upon aircraft type. The effects of timing errors, both vortex induced and random, on tracking accuracy are derived. The fundamental differences between refractive scattering and turbulence scattering techniques are described.

On the Effect of Timing Errors in Run Length Codes

Many redundancy removal algorithms employ some sort of run length code. Blocks of timing words are coded with synchronization words inserted between blocks. The of incorrectly reconstructing a sample because of a channel error in the timing data is a monotonically nondecreasing function of time since the last synchronization word. In this paper we compute the probability that the accumulated magnitude of timing errors equal zero as a function of time since the last synchronization word for a zero-order predictor (ZOP). The result is valid for any data source that can be modeled by a first-order Markov chain and any digital channel that can be modeled by a channel transition matrix. An example is presented.

The Effect of Timing Errors in Optical Digital Systems

The use of digital transmission with narrow light pulses appears attractive for data communications, but carries with it a stringent requirement on system bit timing. The effects of imperfect timing in direct-detection (noncoherent) optical binary systems are investigated using both pulse-position modulation (PPM) and on-off keying for bit transmission. Particular emphasis is placed on specification of timing accuracy and an examination of system degradation when this accuracy is not attained. Bit error probabilities are shown as a function of timing errors from which average error probabilities can be computed for specific synchronization methods. Of significance is the presence of a residual or irreducible error probability in both systems, due entirely to the timing system, which cannot be overcome by the data channel.

Anchor effects in comparative judgment and an analysis of response times

Contrast effects in comparative judgment were demonstrated by a method in which an anchor triangle was interpolated between two objectively equal-sized triangles. In a second experiment RTs were found to vary as a function of anchor extremeness, being fastest when they most deviated in size from the two stimuli to be compared. The effects of time errors were briefly discussed.

On Coded Partially Phase-Coherent Communication Over a Gaussian Channel

Error probabilities for 2northogonal signals under partially phase-coherent reception are derived by a simple method and then illustrated. The amount of phase coherence is related to the efective signal energy per bit to noise density ratio. The joint effect of timing error and noisy phase reference on system performance is examined in detail.

Effect of timing-error on the power spectrum of sampled-data

Effect of timing-error on the power spectrum of sampled-data