Blind phone segmentation based on spectral change detection using Legendre polynomial approximation.

Phone segmentation involves partitioning a continuous speech signal into discrete phone units. In this paper, a method for automatic phone segmentation without prior knowledge of speech content is proposed. The signal spectrum was represented by band-energies. A segment of the band-energy curve was approximated using Legendre polynomial expansion, allowing Legendre polynomial coefficients to describe the properties of the segment. The spectral changes, which imply phone boundaries in the speech signal, were then detected by monitoring the variations of Legendre polynomial coefficients. A two-step algorithm for detecting phone boundaries was derived. The first step was to detect phone boundaries using first-order and second-order coefficients of the Legendre polynomial approximation. The second step was to locate slow spectral changes in the regions of concatenated voiced phones using zero-order coefficients of the Legendre polynomial approximation. This enabled the phone boundaries missed during the first step to be recovered. An evaluation using the TIMIT corpus indicated that the proposed method is comparable to or more accurate than previous methods.

A comparison of delayed self-heterodyne interference measurement of laser linewidth using Mach-Zehnder and Michelson interferometers.

Linewidth measurements of a distributed feedback (DFB) fibre laser are made using delayed self heterodyne interferometry (DHSI) with both Mach-Zehnder and Michelson interferometer configurations. Voigt fitting is used to extract and compare the Lorentzian and Gaussian linewidths and associated sources of noise. The respective measurements are w(L) (MZI) = (1.6 ± 0.2) kHz and w(L) (MI) = (1.4 ± 0.1) kHz. The Michelson with Faraday rotator mirrors gives a slightly narrower linewidth with significantly reduced error. This is explained by the unscrambling of polarisation drift using the Faraday rotator mirrors, confirmed by comparing with non-rotating standard gold coated fibre end mirrors.

Automatic estimation of voice onset time for word-initial stops by applying random forest to onset detection.

The voice onset time (VOT) of a stop consonant is the interval between its burst onset and voicing onset. Among a variety of research topics on VOT, one that has been studied for years is how VOTs are efficiently measured. Manual annotation is a feasible way, but it becomes a time-consuming task when the corpus size is large. This paper proposes an automatic VOT estimation method based on an onset detection algorithm. At first, a forced alignment is applied to identify the locations of stop consonants. Then a random forest based onset detector searches each stop segment for its burst and voicing onsets to estimate a VOT. The proposed onset detection can detect the onsets in an efficient and accurate manner with only a small amount of training data. The evaluation data extracted from the TIMIT corpus were 2344 words with a word-initial stop. The experimental results showed that 83.4% of the estimations deviate less than 10 ms from their manually labeled values, and 96.5% of the estimations deviate by less than 20 ms. Some factors that influence the proposed estimation method, such as place of articulation, voicing of a stop consonant, and quality of succeeding vowel, were also investigated.

Laser ultrasonic evaluation of human dental enamel during remineralization treatment.

In this work a non-destructive laser ultrasonic technique is used to quantitatively evaluate the progressive change in the elastic response of human dental enamel during a remineralization treatment. The condition of the enamel was measured during two weeks treatment using laser generated and detected surface acoustic waves in sound and demineralized enamel. Analysis of the acoustic velocity dispersion confirms the efficacy, as well as illuminating the progress, of the treatment.

Noncontact, nondestructive elasticity evaluation of sound and demineralized human dental enamel using a laser ultrasonic surface wave dispersion technique.

Laser ultrasonic nondestructive evaluation (NDE) methods have been proposed to replace conventional in vivo dental clinical diagnosis tools that are either destructive or incapable of quantifying the elasticity of human dental enamel. In this work, a laser NDE system that can perform remote measurements on samples of small dimensions is presented. A focused laser line source is used to generate broadband surface acoustic wave impulses that are detected with a simplified optical fiber interferometer. The measured surface wave velocity dispersion spectrum is in turn used to characterize the elasticity of the specimen. The NDE system and the analysis technique are validated with measurements of different metal structures and then applied to evaluate human dental enamel. Artificial lesions are prepared on the samples to simulate different states of enamel elasticity. Measurement results for both sound and lesioned regions, as well as lesions of different severity, are clearly distinguishable from each other and fit well with physical expectations and theoretical value. This is the first time, to the best of our knowledge, that a laser-based surface wave velocity dispersion technique is successfully applied on human dental enamel, demonstrating the potential for noncontact, nondestructive in vivo detection of the development of carious lesions.

Laser ultrasonic surface wave dispersion technique for non-destructive evaluation of human dental enamel.

This paper describes a novel optical system for clinical diagnosis of dental enamel based on its elasticity. Current examination techniques are typically destructive, and frequently impractical for in-vivo inspection. This paper describes the first application of a laser ultrasonic non-destructive evaluation (NDE) method for clinical dental diagnosis. It performs remote elasticity evaluation on small dimension samples. A focused laser line-source generates broadband surface acoustic wave (SAW) impulses which are detected with a simplified optical fibre interferometer. The measured SAW velocity dispersion spectrum was in turn used to characterise the elasticity of the specimen. Different metal structures were measured to verify the system performance. The results agree well with theoretical values and confirm the reliability and accuracy of the laser NDE system. This technique was then applied to evaluate the surface of sound natural human dental enamel. The measured dispersion spectra match theoretical expectations and the influences of both the enamel and the underlying dentin on the surface wave propagation were observed. This is the first time, to the best of our knowledge, that a laser based SAW velocity dispersion technique has been successfully applied on human dental enamel. As a remote, non-destructive technique it is applicable in-vivo and opens the way for early diagnosis of dental caries.

Simple, all-optical, noncontact, depth-selective, narrowband surface acoustic wave measurement system for evaluating the Rayleigh velocity of small samples or areas.

In this paper a new ultrasonic testing system is described that utilizes noncontact optical methods to generate and detect surface acoustic waves (SAWs) and has significant applications in the nondestructive evaluation of surface material. A narrowband SAW is generated with a new and straightforward grating mask image projection method that provides fast switching and a controllable frequency band, and hence control of the penetration depth of the ultrasonic wave. A narrowband SAW with center frequency above 30 MHz, and hence better depth resolution, is generated. The detection of the SAW is performed with a simplified design of an optical fiber interferometer that has good sensitivity and manoeuvrability without requiring additional auxiliary components. The novel combination of these two optical techniques permits the measurement of small samples that are otherwise difficult to measure, especially nondestructively. A model was constructed to simulate the temporal characteristics of the generated narrowband SAW and showed good agreement with experiment. Measurements on an aluminum sample and an extracted human incisor demonstrate the system's performance.

New speech harmonic structure measure and its applications to speech processing.

The harmonic structure can be easily recognized in time-frequency representation of speech signals in adverse environment. The harmonicity is a measure of the completeness of a harmonic structure. This paper presents a new harmonic structure measure that extends the conventional harmonicity to a set of harmonicities. They are expressed in terms of the grid harmonicity, the temporal harmonicity, the segment-spectral harmonicity, and the segmental harmonicity. The grid harmonicity measures the completeness of individual harmonics in each frame. The grid harmonicities in a frame are summed up to form a temporal harmonicity for representing the strength of harmonicity. The segment-spectral harmonicity, computed by summing specific grid harmonicity over a segment, evaluates the integrity of individual harmonics across a segment. The segmental harmonicity evaluates the total strength of harmonic structure within a segment. This set of harmonicities is available for a systematic analysis of the harmonic structure and effective to several speech processing tasks. The applications to speech distortion analysis, robust fundamental frequency estimation, robust voicing detection, and speech enhancement are demonstrated.

High-power figure-of-eight fiber laser with passive sub-ring loops for repetition rate control.

The operation of an erbium figure-of-eight all-fiber laser with a fundamental repetition rate of 5.68 MHz, peak power of 0.7 kW and pulse width of 420 fs is reported. Four times the fundamental repetition rate is achieved with two passive sub-ring loops at a repetition rate of 22.8 MHz. The sub-ring loop consists of only a single-mode fiber coupler with an input port and output port connected so as to make the time delay an odd multiple half-period of the input pulse period. This method is simple and inexpensive when compared with conventional methods employing sub-ring cavity or special fiber Bragg grating to control repetition rate.