The Pohlman cell as as a means of producing acoustic holograms

This paper reports the application of acoustic holography to a previously used non-destructive testing technique — the Pohlman Cell.     

Half tone dot reproduction as a means of lens testing

A simple relationship was sought between lens MTF and the results of photographing half-tone dot patterns. Qualitative understanding was more important than quantitative accuracy, and therefore emphasis was laid on developing an inexact but helpful model. This was successful and has thrown useful light on the results which had been observed.     

Effect of tones on vocal attack time in Cantonese speakers

Vocal attack time (VAT) is the time lag between the growth of the sound pressure signal and the development of physical contact of vocal folds at vocal initiation. It can be derived by a cross-correlation of short-time amplitude changes occurring in the sound pressure and electroglottographic (EGG) signals. Cantonese is a tone language in which tone determines the lexical meaning of the syllable. Such linguistic function of tone has implications for the physiology of tone production. The aim of the present study was to investigate the possible effects of Cantonese tones on VAT. Sound pressure and EGG signals were simultaneously recorded from 59 native Cantonese speakers (31 females and 28 males). The subjects were asked to read aloud 12 disyllabic words comprising homophone pairs of the six Cantonese lexical tones. Results revealed a gender difference in VAT values, with the mean VAT significantly smaller in females than in males. There was also a significant difference in VAT values between the two tone categories, with the mean VAT values of the three level tones (tone 1, 3, and 6) significantly smaller than those of the three contour tones (tone 2, 4, and 5). The findings support the notion that norms and interpretations based on nontone European languages may not be directly applied to tone languages.     

Development and evaluation of methods for assessing tone production skills in Mandarin-speaking children with cochlear implants

The aim of the study was (1) to develop methods for evaluating tone production of children with cochlear implants (CIs) who speak Mandarin Chinese and (2) to evaluate the efficacy of using these methods to assess tone production. The subjects included two groups of native-Mandarin-Chinese-speaking children: 14 prelingually deafened children who had received CIs and 61 normal-hearing (NH) children as controls. The acoustic analysis focused on quantification of the degree of differentiation among lexical tones based on tonal ellipses and the overall similarity of tone contours produced by the children with CIs to normative contours derived from the 61 NH children. An artificial neural network was used to recognize tones produced by the children with CIs after trained with tone tokens produced by the NH children. Finally, perceptual judgments on the tone production of both groups were obtained from eight native-Mandarin-speaking NH adults to evaluate the efficacy of the methods. The results showed that all measures using the acoustic, neural-network, and perceptual analyses were highly correlated with each other and could be used to effectively evaluate tone production of children with CIs.     

Simulating the open-loop transfer function as a means for understanding acoustic feedback in hearing aids

Suppressing unstable acoustic feedback in hearing aids will first require knowledge of the open-loop transfer functions of such systems. Reported herein is a mathematical technique for simulating the open-loop transfer function of an in situ eyeglass-type hearing aid. In particular, a computer program was developed that characterized the hearing aid as a serial connection of two-port blocks, each representing one individual component of a hearing aid. Included, for example, were two-port blocks representing the microphone, amplifier, receiver, sound tubes leading to the eardrum (including the ear canal itself), earmold vent, and external pathway from the vent outlet back to the microphone. The computer program was validated by replicating laboratory data derived from an experiment involving a nonstandard manikin fitted with a nonstandard artificial ear. Next, the open-loop transfer function of an eyeglass-type hearing aid in situ on the manikin was simulated via the computer program. Unfortunately, those computer-generated data were not replicated in the laboratory due to the difficulty encountered in actually measuring the open-loop transfer function. Nevertheless, investigators were able to utilize those data to predict, within +/- 25 Hz, the "squeal" frequency of unstable acoustic feedback.     

Utilisation of on-line acoustic irradiation as a means to counter-effect catalyst deactivation in heterogeneous catalysis

The effect of power ultrasound has been studied in the hydrogenation of 1-phenyl-1,2-propanedione (enantioselective hydrogenation) and linoleic acid (fat hardening). Furthermore the hydrogenation of d-xylose to xylitol and citral to citronellal and citronellol were studied under the influence of acoustic irradiation. We have investigated the effect of on-line acoustic irradiation of these heterogeneously catalysed liquid-gas-solid systems in which it was found to counter-effect catalyst deactivation, increase the reaction velocity and to enhance the selectivity of various heterogeneously catalysed reactions.     

An acoustic analysis of fluctuations in the voices of normal adult speakers across three times of day

The purpose of this study was to determine the amount of variation for several vocal parameters across three times of the day (morning, noon, and afternoon). Connected speech samples from normal adult males (N = 10) and females (N = 10) were recorded during morning, early afternoon, and late afternoon. Results showed that males produced a statistically significant increase in speaking fundamental frequency (SFF) from morning to afternoon. Females did not demonstrate a statistically significant change in SFF across the three time periods. Vocal amplitude did not change significantly for either group. The SFF variability was higher for the females than for the males. Analysis of individual data revealed that the patterns of vocal change across the three times of day were not consistent among the subjects.     

Cochlear mechanics: analysis for a pure tone

A three-dimensional hydroelastic model of the cochlea is analyzed, in which the fluid is viscous and the basilar membrane is an inhomogeneous orthotropic elastic plate. After the solution is obtained using a multiple-scale approximation, comparison is made with experiment for the human cochlea.     

The optical parametric oscillator as a means for intracavity absorption spectroscopy

In view of the recent progress in the detection of narrow and weak absorption lines as provided by the intracavity technique which utilizes lasers with broad homogeneous emission lines, it appears to interesting to investigate also other light sources with regard to their suitability for intracavity spectroscopic measurements. A promising candidate is an optical parametric oscillator (OPO) pumped by a one-mode field and oscillating in several signal and idler modes, since, as will be shown, this light source exhibits a strong competition effect which, as known from the laser, gives rise to a drastic enhancement in detection sensitivity. In this paper, we calculate the enhancement factor utilizing a simple OPO model which takes account of the spontaneous production of signal and idler photons (parametric fluorescence). The result is similar to that for a laser operated such that spontaneous emission is the only mechanism which prevents a mode with higher losses to be extinguished. Moreover, the OPO offers a possibility to perform the measurement at a frequency which is complementary (with respect to the pump frequency) to the frequency of the absorption line to be detected.     

A comparison of intergestural patterns in deaf and hearing adult speakers: implications from an acoustic analysis of disyllables.

Coarticulation studies in speech of deaf individuals have so far focused on intrasyllabic patterning of various consonant-vowel sequences. In this study, both inter- and intrasyllabic patterning were examined in disyllables /symbol see text #CVC/ and the effects of phonetic context, speaking rate, and segment type were explored. Systematic observation of F2 and durational measurements in disyllables minimally contrasting in vocalic ([i], [u,][a]) and in consonant ([b], [d]) context, respectively, was made at selected locations in the disyllable, in order to relate inferences about articulatory adjustments with their temporal coordinates. Results indicated that intervocalic coarticulation across hearing and deaf speakers varied as a function of the phonetic composition of disyllables (b_b or d_d). The deaf speakers showed reduced intervocalic coarticulation for bilabial but not for alveolar disyllables compared to the hearing speakers. Furthermore, they showed less marked consonant influences on the schwa and stressed vowel of disyllables compared to the hearing controls. Rate effects were minimal and did not alter the coarticulatory patterns observed across hearing status. The above findings modify the conclusions drawn from previous studies and suggest that the speech of deaf and hearing speakers is guided by different gestural organization.     

A study of sentence stress production in Mandarin speakers of American English

Acoustic characteristics of American English sentence stress produced by native Mandarin speakers are reported. Fundamental frequency (F0), vowel duration, and vowel intensity in the sentence-level stress produced by 40 Mandarin speakers were compared to those of 40 American English speakers. Results obtained from two methods of stress calculation indicated that Mandarin speakers of American English are able to differentiate stressed and unstressed words according to features of F0, duration, and intensity. Although the group of Mandarin speakers were able to signal stress in their sentence productions, the acoustic characteristics of stress were not identical to the American speakers. Mandarin speakers were found to produce stressed words with a significantly higher F0 and shorter duration compared to the American speakers. The groups also differed in production of unstressed words with Mandarin speakers using a higher F0 and greater intensity compared to American speakers. Although the acoustic differences observed may reflect an interference of L1 Mandarin in the production of L2 American English, the outcome of this study suggests no critical divergence between these speakers in the way they implement American English sentence stress.     

Characteristics of thermal acoustic radiation as a source of acoustic signals

A linear dependence of the output voltage of an acoustic thermometer on the temperature difference between the source and the piezoelectric transducer is demonstrated experimentally. The constant component of the output voltage is determined by the noise temperature of the receiving device. The main feature of the thermal acoustic radiation as a source of acoustic signals is that the signal is represented not by the total thermal radiation of the object, which is proportional to the absolute temperature of the latter, but by the part of this radiation that is proportional to the temperature difference between the object and the transducer.     

声波测井压电振子的有限元分析

压电振子是新一代方位声波测井仪器中相控圆弧阵声波辐射器的重要组成部分。利用有限元法对构成圆弧阵的压电振子进行了设计分析,结果显示了压电振子存在多阶弯曲振动模态,且长度方向一阶弯曲振动能够满足方位声波测井的工作频率要求。针对长度方向一阶弯曲振动模式,数值模拟了几何尺寸对压电振子性能参数的影响。压电振子的谐振频率随着陶瓷片长度、基片或陶瓷片厚度的减小而降低;压电振子的辐射声功率随着陶瓷片长度或压电振子宽度的增加、基片或陶瓷片厚度的减小而增大;合理地选取长度和厚度可使压电振子具有较高的机电耦合系数。数值模拟结果可以对圆弧阵结构优化设计起到良好的指导作用。     

The use of acoustic fields as a filtration and dewatering aid

An experimental rig has been developed to study the effects of electric and acoustic field combinations on the filtration rate of titanium dioxide suspensions. Ultrasound energy is applied tangentially to the filter medium. Electric field strengths, suspension characteristics and process parameters can all be varied independently. Results from an experimental programme demonstrate that the use of ultrasound across the cake surface can decrease the specific cake flow resistance and increase the filtration rates of low-concentration rutile suspensions (0.1% v/v). Changes in the conductivity induced by ultrasonic irradiation affect the suspension such that the application of an electrical field is enhanced, giving an equivalent electric field strength higher than that applied.     

Intra-operative acoustic hemostasis of liver: production of a homogenate for effective treatment

Objective: We have shown that High-Intensity Focused Ultrasound (HIFU) can effectively control bleeding from injuries to solid organs such as liver, spleen, and lung. Achievement of hemostasis was augmented when a homogenate of tissue and blood was formed. The objective of this study was to investigate quantitatively the effect of homogenate production on HIFU application time for hemostasis. Possible mechanisms involved in homogenate production were also studied.Methods: Ten anesthetized rabbits had laparotomy and liver exposure. Liver incisions, 15-25 mm long and 3-4 mm deep, were made followed immediately by HIFU application. Two electrical powers of 80 and 100 W corresponding to focal acoustic intensities of 2264 and 2829 W/cm², respectively were used. Tissue and homogenate temperatures were measured. Smear and histological tissue sample analysis using light microscopy were performed.Results: In treatments with homogenate formation, hemostasis was achieved in 76 ± 1.3 s (Mean ± Standard Error Mean: SEM) at 80 W. In treatments without homogenate formation (at 80 W), hemostasis was achieved in 106 ± 0.87 s. At 100 W, hemostasis was achieved in 46 ± 0.3 s. The time required for homogenate formation, at 80 and 100 W were 60 ± 2.5 and 23 ± 0.3 s, respectively. The homogenate temperature was 83 °C (SEM 0.6 °C), and the non-homogenate tissue temperature at the treatment site was 60 °C (SEM 0.4 °C). The smear and histological analysis showed significant blood components and cellular debris in the homogenate, with some intact cells.Conclusion: The HIFU-induced homogenate of blood and tissue resulted in a statistically significant shorter HIFU application time for hemostasis. The incisions with homogenate had higher temperatures as compared to incisions without homogenate. Further studies of the correlation between homogenate formation and temperature must be done, as well as studies on the long-term effects of homogenate in achieving hemostasis.     

Compensation for pitch-shifted auditory feedback during the production of Mandarin tone sequences

Recent research has found that while speaking, subjects react to perturbations in pitch of voice auditory feedback by changing their voice fundamental frequency (F0) to compensate for the perceived pitch-shift. The long response latencies (150-200 ms) suggest they may be too slow to assist in on-line control of the local pitch contour patterns associated with lexical tones on a syllable-to-syllable basis. In the present study, we introduced pitch-shifted auditory feedback to native speakers of Mandarin Chinese while they produced disyllabic sequences /ma ma/ with different tonal combinations at a natural speaking rate. Voice F0 response latencies (100-150 ms) to the pitch perturbations were shorter than syllable durations reported elsewhere. Response magnitudes increased from 50 cents during static tone to 85 cents during dynamic tone productions. Response latencies and peak times decreased in phrases involving a dynamic change in F0. The larger response magnitudes and shorter latency and peak times in tasks requiring accurate, dynamic control of F0, indicate this automatic system for regulation of voice F0 may be task-dependent. These findings suggest that auditory feedback may be used to help regulate voice F0 during production of bi-tonal Mandarin phrases.     

Using acoustic emission signals for monitoring of production processes

The systems for in-process quality assurance offer the possibility of estimating the workpiece quality during machining. Especially for finishing processes like grinding or turning of hardened steels, it is important to control the process continuously in order to avoid rejects and refinishing. This paper describes the use of on-line monitoring systems with process-integrated measurement of acoustic emission to evaluate hard turning and grinding processes. The correlation between acoustic emission signals and subsurface integrity is determined to analyse the progression of the processes and the workpiece quality.