bluuebunny/crossref_metadata_2025 huggingface dataset:
Possibility of bottom-layer parameter reconstruction using acoustic signals of the THETIS-2 experiment
Authors: Fokin Vladimir N. , Fokina Margarita S. , Morozov Andrey K.
Published: October 2005

During an international acoustic tomography experiment, which had been deployed in the western Mediterranean in 1994, acoustic measurements with vertical arrays were made from autonomous bottom modules. Due to near-bottom signal receiving, a number of time-separated bottom reflected and refracted signals were obtained after correlation processing. One of the short-range observation points was chosen to investigate the possibility of using THETIS-2 signals for bottom parameter reconstruction. Using distribution and inverse methods, sound-speed profiles in the upper bottom layer were reconstructed. Analysis of the possibility to obtain signals at ranges up to 200 km from autonomous bottom modules for use in bottom parameters reconstruction was performed. [Work supported by RFFI Project N 96-02-18944.]
Influence of bottom characteristics on the differential tomography method in the deep ocean
Authors: Fokin Vladimir N. , Fokina Margarita S.
Published: October 2005

The method of differential tomography is based on the fact that the mean velocity of sound pulse propagation along the ray trajectory depends on the angle of the ray exit. The method efficiency is analyzed numerically for the signal reception to a horizontal array and a single hydrophone. It is shown that the signal of illumination may be suppressed and the scattered signal may be separated by time gating. It is also shown that the depth of the deposition of a space-localized inhomogeneity may be estimated by the width of the scattered signal autocorrelation function. The distance to the inhomogeneity may be defined by the cross-correlation function of the scattered signal at various array receivers. The influence of bottom characteristics, the depth of the submergence of a scatterer, and the distance between a source and a receiver on the scattered signal structure is analyzed. [Work supported by RFFI Project N 96-02-18944.]
Diagnosis of the prosthetic cardiac valve by the characteristics of audible and ultrasonic closing click
Authors: Hasegawa Jun , Kobayashi Kenji , Matsumoto Hiroshi
Published: October 2005

For the post-operative treatment of the prosthetic cardiac valve, its closure click was measured clinically. Ultrasonic range signal components, as well as the widely known audible signal components were found to exist. The frequency range of the ultrasonic click was from 8 kHz to more than 600 kHz, while that of the audible click was up to 8 kHz. Both of the clicks included effective diagnostic information. The Wigner distribution (WD) of the audible closing click offered the possible indices of thrombus and/or sclerosis. Especially, the first-order local moment of the WD showed capability for the quantitative diagnosis of the thrombosed valve. The ultrasonic closing click offered more diagnostic information for the bileaflet valve, while it also had sensitivity for the thrombosed valve. Since the waveform of the ultrasonic click indicated clearly the instance of the valve closing, it also revealed the exact time difference between the closing time of each leaflet, which could be used as the indices of bileaflet valve malfunction. With those characteristics of the closing click, detailed diagnosis of the prosthetic cardiac valve malfunction could be determined.
Clinical application of joint noise analysis in the evaluation of internal derangement and degenerative changes of the temporomandibular joint
Authors: Ishigaki Shoichi , Bessette Russell W. , Maruyama Takao
Published: October 2005

The evaluation of temporomandibular joint (TMJ) sounds has been considered as an integral part of the physical examination for temporomandibular disorders (TMD). To evaluate the usefulness of TMJ vibration analysis, 297 joints from TMD patients were diagnosed by lower joint arthrography and videofluoroscopy. The surface vibrations of TMJ were recorded with electovibratography. The following four conditions were statistically discriminated by multivariate analyses of the frequency components: (I) meniscal displacement with reduction; (II) meniscal displacement with partial disk reduction; (III) meniscal displacement without reduction; and (IV) degenerative joint disease and/or perforation of the disk. Using the total vibration energy as a threshold, the diagnostic sensitivity was 82%, while the diagnostic specificity was 75%. Discriminate analysis for the above-mentioned four conditions revealed the diagnostic sensitivity of 79%, 80%, 77%, and 76%, and the diagnostic specificity of 76%, 86%, 59%, and 78% for conditions I, II, III, and IV, respectively. It was concluded that the vibration analysis of the TMJ could be clinically useful as a routine examination tool for TMD patients.
Modern mysteries of lung sounds
Authors: Kraman Steve S.
Published: October 2005

The last 20 years have seen the clarification of a number of questions about the sources, mechanisms, and diagnostic meaning of lung sounds. These include the specificity of fine and coarse crackles for different diseases; the normal distribution of lung sounds over the chest; and the likely location of the source of the normal lung sound within the airways. Nevertheless, no instrument or signal processing scheme has yet proved to be more effective for analyzing lung sounds than the stethoscope. Several fundamental questions remain mysterious. They are: The mechanisms that produce the normal lung sounds (which appear to be remarkably independent of gas density); the causes of the inhomogeneous distribution of normal lung sounds over the chest wall; the reason that lung sounds are faint or absent in emphysema; and through what pathway(s) airway-generated lung sounds reach the chest wall. These questions must be answered before computer-aided lung sound analysis can fulfill its promise to reveal more information about pulmonary physiology and pathology than is now possible by ear alone.
Acoustical correlates of air flow obstruction in children
Authors: Pasterkamp Hans
Published: October 2005

Airway obstruction is common during childhood and is often identified by acoustical signs. Vibration of airway walls in narrowed passages is a presumed mechanism of wheeze, a typical sound in patients with asthma and bronchiolitis. Other sources may include the oscillatory motion of airway secretions. Considering the significance of wheeze for epidemiological classifications, surprisingly little information exists about acoustical characteristics. Wheezing varies with age. Infants tend to have less musical sounds and complex repetitive sound waves compared with more regular sinusoidal patterns in older asthmatics. Children may not wheeze even when flow is significantly obstructed. However, normal lung sounds change during flow obstruction even without wheeze. Intensity at low frequencies (100–300 Hz) is typically reduced during obstruction while medium (300–600 Hz) and high frequency (600–1200 Hz) sounds—which are more affected by gas density and thus likely reflect turbulent flow—often increase. Compared with spirometry, measurements of respiratory sound can uncover flow obstruction in children without the need for forced breathing. Technical and theoretical questions remain, e.g., about sensors for noisy environments and about changes in thoracic sound transmission during bronchoconstriction. Nevertheless, acoustic measurements can provide a noninvasive diagnostic option with special usefulness in children.
Blood vessels acoustical diagnostics at the echolocation mode
Authors: Oboznenko E. I. , Oboznenko I. L.
Published: October 2005

Blood vessels biomechanical models in the form of multilayered anizothropic viscoelastic cylindrical shells with viscoelastic compressible biotissue from their one side and blood flow (taken as a compressible visco-elastic fluid) from the other side have been built. The vessels’ acoustical resonant and antiresonant frequencies for middle-sized and large arteriole (veinlet), artery (vein), and aorta, both within the vacuum and within their biological medium, have been detected. Blood vessels’ models that imitate such pathologies as arteriosclerosis and diabetes are elaborated. The informative frequency range for these vessels pathologies lays within 60 Hz–6 MHz. The lower spectrum of the range deals with the large vessels, the upper one deals with middle-sized and small vessels. The most probable detected vessels’ acoustical resonances respond to the first three oscillation modes. Thanks to the fact that blood vessels have an elastic modulus less by the factor 10E3⋅⋅⋅10E6, then the well-known ‘‘metallic’’ or plastic shells’ elastic moduli, their (vessels’) dispersion characteristic as well as their modus of interaction between the moving blood column oscillations and the vessel itself, has quite a different character. This is due to the low sound propagation velocity of the longitudinal and shear waves in the vessel when compared with the velocity of the same waves within the viscoelastic blood. A diabetes case is detected by blood viscosity changes, that cause the obvious (up to 30%) vessel’s main resonance shift. Arteriosclerotic pathologies cause the appearance of an extra two or three resonances next to the main resonance of the vessel given, and they can be detected in the echosignal when compared to this vessel type anatomical standard that is filed in a computer database. Blood flow rate determination in the vessel is a trivial procedure. The suggested technique has been approved in vitro on the canina vessels’ models and is confirmed in clinical conditions (with real patients).
Characteristics of blood flow noise generated by cerebrovascular deformations
Authors: Kobayashi Kenji , Hasegawa Jun
Published: October 2005

A noninvasive detection system for cerebrovascular disease such as aneurysms, stenosis, and occlusions has been developed by using a specially designed PVDF-film sensor and signal analysis based on FFT and the Wigner distribution. About 90 patients with cerebrovascular diseases and 30 normal persons were measured at the Department of Neurosurgery, Ube Industries Central Hospital. FFT spectral differences between patients and normal persons exist over the frequency range from 0.5 to 1.2 kHz. In particular, the differences in spectral components between 750 Hz and 1.5 kHz could be the possible index for diagnosis of the existence of cerebrovascular disease. The FFT spectral pattern showed some differences between stenosis and aneurysms. In stenosis, it seemed that there existed a flat level from 0.4 to 2.2 kHz, while in aneurysms the power decreases smoothly from the peak around 0.7 kHz. Time variance of the blood flow noise according to the cardiac cycle could be seen in the stenosis from 30% to 50%, but not in the cases from 40% to 90%.
Diagnosis of heart muscle by spectrum transition estimation of heart wall vibration
Authors: Sato Michie , Kanai Hiroshi , Chubachi Noriyoshi , Koiwa Yoshiro
Published: October 2005

Vibration of the heart wall arises from motion due to myocardial contraction and relaxation, and thus this vibration reflects the function of the heart. The activity of the heart muscle can be estimated by investigating the spectrum transition of spatial and/or frequency spectra between vibration signals. It is difficult, however, to estimate the spectrum transition patterns of nonstationary signals, such as vibration, and to diagnose heart diseases. A new method of the estimation of spectrum transition is presented by introducing a constraint into the cost function, which is described by the partial correlation coefficients, by constraint least-squares method. By applying this method to the analysis of vibration signals, noninvasively measured by a method developed in our laboratory using ultrasonics, on the left ventricular side of the interventricular septum, the spectrum transition during a period of one beat was investigated. Furthermore, by analysis of some vibration signals on the vertical cross section of the interventricular spectrum between the right and left ventricles, the spectrum transition of the myocardial layers was investigated and the spectrum transition patterns of normal individuals and patients were clearly obtained. The establishment of this method opens up a new way of diagnosing heart diseases.
Development of a site targeted acoustic contrast agent for improved medical ultrasonic diagnosis
Authors: Lanza Gregory M. , Wallace Kirk D. , Scott Michael J. , Trousil Rebecca L. , Miller James G. , Gaffney Patrick J. , Wickline Samuel A.
Published: October 2005

A novel site targeted acoustic contrast agent with the potential to define and localize a myriad of pathological tissues for diagnosis or therapy has been developed. The agent is a lipid-coated perfluorocarbon microemulsion modified to accommodate avidin–biotin conjugation. The formulation has low inherent echogenicity in suspension, yet high acoustic reflectivity after binding to a surface or itself. Targeted and control emulsions were suspended in buffered saline and imaged with a 7.5-MHz linear array transducer. Neither suspension manifested significant ultrasonic backscatter until avidin was added. Avidin induced aggregation and produced a marked enhancement in backscatter from the targeted but not from the control emulsion. Targeted and control emulsions were exposed to avidin conjugated nitrocellulose membranes and imaged with a high-resolution 50-MHz acoustic microscope. Bound targeted emulsion produced a fourfold enhancement in the magnitude of ultrasonic backscatter (+6.3 dB) from the membrane relative to the control (p<0.05). Moreover, acoustic contrast targeted to thrombi bothin vitro and in vivo using antifibrin monoclonal antibodies markedly enhanced (p<0.05) their acoustic reflectivity. These data demonstrate the first site targeted acoustic contrast agent and suggest potential improvement in the ultrasonic diagnosis of thrombi and other pathology.
In vivo measurements of lithotripsy shock waves in pigs
Authors: Cleveland Robin O. , Crum Lawrence A. , Lifshitz David A. , Connors Bret A. , Evan Andrew P.
Published: October 2005

Mechanisms of stone comminution and tissue damage in lithotripsy are sensitive to the acoustic field within the kidney, yet prediction of shock wavesin vivo is difficult. Measurements of lithotripsy shock waves have been made inside pigs with small hydrophones constructed of a 50-μm PVdF membrane stretched over a 21-mm-diam ring. A thin layer of silicone rubber was used to electrically isolate the membrane from pig fluid. An incision was made in the pig flank and a hydrophone inserted either on the anterior (shock wave entrance) or posterior (shock wave exit) surface of the left kidney. The incision was flooded with saline during closure to minimize entrapped air. Four pigs were treated in a Dornier HM-3 lithotripter. Fluoroscopic imaging was used to orient the hydrophone perpendicular to the shock wave. For each pig, various power settings and movement of the shock wave focus throughout the kidney were used. Waveforms measured within the pig had a shape very similar to those measured in water. However, pressure amplitude in the pig was about 60% of that measured in water. The shock rise times were on the order of 100 μs and were hydrophone limited. [Work supported by NIH and the ASA Hunt Fellowship.]
Assessment and design of product sound
Authors: Lyon Richard H.
Published: October 2005

Quantitative algorithms for the calculation of loudness or A-weighted sound power levels are useful to product companies for meeting regulatory or advertising needs. Most consumer product companies recognize however that these measures are inadequate for determining customer satisfaction with product sound. Newer algorithms that compute quantities such as roughness and sharpness have been introduced and are now fairly widely available. A common inadequacy of all such algorithms is their inability to incorporate cognitive aspects of product sound. This presentation will describe a procedure for converting consumer judgments of product sounds into design requirements for the components. The procedure involves jury testing, using combinations or ‘‘mixes’’ of component sounds. The experimental design, jury training, experimental protocol, and response analysis are described. Finally, an example of the way the results of the procedure are converted to design goals will be presented.
Sound quality assessment: Listener selection and training
Authors: Letowski Tomasz
Published: October 2005

Sound quality assessment is a sound measurement process whereby the sound characteristics are the unknown quantity and the listener is the measuring tool. This concept of sound assessment applies to both signal quality and noise quality studies. The groups of listeners assessing sound quality in such studies are called listening groups. The listening groups are usually small and frequently created on an ‘‘ad-hoc’’ or statistical basis. This is an unfortunate situation because human auditory capabilities vary greatly among individuals and depend on the psychophysiological profile, experience, and listening skills of the listener. Therefore, the composition of the listening group should be considered the primary factor affecting the results of sound quality assessment. To increase the practical value of sound quality studies, the issue of selection and training of the listeners must be given more attention. For example, it should be recognized that sound quality studies are different from marketing studies and need to involve uniform groups of listeners. It is also imperative that the difficulty and complexity of the listening tasks are proportional to the listener’s auditory skills and knowledge of the subject matter.
Assessment of rough sounds by Japanese listeners using a combined psychoacoustical and socioacoustical approach
Authors: Weber Reinhard , Schulte-Fortkamp Brigitte , Kuwano Sonoko , Namba Seiichiro , Schick August
Published: October 2005

Sufficiently fast periodic amplitude or frequency variations of sounds may lead to roughness sensations with a negative effect on the perceived acoustic quality. That is a reason why roughness investigations gain much attention in sound quality research. Roughnesses of modulated synthesized sounds and technical noises are assessed by Japanese listeners in a classroom and in a laboratory experiment with a combined method of scaling and intermittent thinking aloud (ITA). Seventy-five short noises are presented in three consecutive blocks of 25 each, with long pauses between the blocks. The test subjects are asked to categorically assess the roughness of the sounds presented after they have been introduced to the concept of roughness by examples of typical rough sounds. After 25 noises are presented, the subjects are asked to write down what is going through their minds at that moment (ITA). At the end of the noise presentations the subjects answer an additional questionnaire concerning the sounds and the experimental situation. In the classroom experiment 202 students perform the difficult experimental tasks. Ten subjects repeat identical tasks in the laboratory when assessing roughness and pleasantness.
Sound quality design of vehicle noise
Authors: Hashimoto Takeo , Hatano Shigeko , Takada Masayuki
Published: October 2005

In order to improve sound quality of vehicle noise, the idling exterior noise of a small diesel engine truck and the interior noise of a small-size sedan were varied artificially using a digital signal-processing technique in the frequency domain. First, the original exterior idling noise and its variations were tested using a paired-comparison technique concerning their unpleasantness. As a result, the reduction of the high-frequency component, i.e., −6 dBA compared with the original, was most effective in reducing unpleasantness of exterior idling noise. To realize this effect in a very small diesel engine truck, an engine compartment enclosure was fixed to the original truck. The result was quite successful in achieving a significant reduction in the high-frequency noise component. Second, interior noises of a small size sedan with four cylinders and a four-cycle engine were varied in their second-order component of engine revolutions and their booming sensation was tested using magnitude estimation and categorical judgment in seven categories in the requirement of improvement. It was clarified that the reduction of the second-order component gave a significant reduction in booming sensation. In addition to the subjective experiments, the relation between the subjective results and the psychoacoustical measures was also considered.
On the standardization of metrics for sound quality assessment
Authors: Davies Patricia , Ebbitt Gordon , Laux Peter C.
Published: October 2005

There is interest in the use of sound quality metrics as aids in the design of the sounds that machines make. Assessment of aspects of sound quality by subjective testing is time consuming and difficult to perform; unintentional biases may be introduced into the test and comparisons of results from different tests are difficult to make, due to the changing criteria that people may use to judge the sounds. Currently available commercial instrumentation calculates many of these metrics, but, due to the absence of standards, different systems produce different results. Many metrics are based on a measure of time-varying loudness, and its calculation is not standardized either. A summary of the current status of metric calculation is given with examples taken from some commercially available hardware systems. Options for future directions will also be explored.
Effect of exhaust pipe connection on the exhaust noise of an internal combustion engine
Authors: Kido Ken’iti , Kawahami Kazuhisa , Suzuki Hideo , Ona Tatsuo
Published: October 2005

It has been considered that the fundamental frequency of the exhaust noise of an internal combustion engine is the inverse of the number of firings per second. However, in most of the data measured with automobiles, there are many frequency components of 1/2, 1/4, or 1/6 of the fundamental frequency and their higher harmonics. An investigation on the generation of such frequency components is reported. It was found that the differences in the lengths of the exhaust pipes generate such frequency components. This paper describes, first, the reduction of the theoretical equation in which the phase modulation in the exhaust noise due to the difference in the length of the exhaust pipe of each cylinder generates such frequency components. The spectra which have the same frequency components as the spectra of the measured exhaust noise are obtained by numerical computation of the equation. The same results are also obtained by computer simulations. The difference in sound quality is felt by hearing the synthesized sound. It is expected that this study is usable in realizing an engine of agreeable exhaust noise quality.
A study of the correlation between objective and subjective measures of steady-state refrigerator noise
Authors: May Philip G. , Davies Patricia , Bolton J. Stuart , Kim Sungjin
Published: October 2005

In preliminary studies [May et al., Proc. INTER-NOISE 96 (1996)] it was found that subjective human response (annoyance) to refrigerator noise could be predicted well using a model based on three objective signal metrics. The first study involved 24 subjects, half with a Korean background and half with an American background, and 17 refrigerator signals. The subjects of Korean background exhibited a heightened sensitivity to the noises. A second study used 24 subjects, all with an American background, and 12 signals. Paired comparison and parametric tests produced similar results. A third study investigated the feasibility of deriving a general purpose objective model to predict annoyance due to steady-state refrigerator noise. A larger range of signals was used to better represent refrigerator noises likely to be encountered in practice. The increased number of signals made paired comparison tests impractical and thus only the similarly effective parametric tests were performed. Linear combinations of signal metrics yielded models with R2 values higher than 0.8, indicating a high degree of predictability. [Work supported by LG Electronics and GE Appliances.]
Evaluation of the subjective effects for active noise control
Authors: Shoji Atsuko , Hamada Hareo
Published: October 2005

Active noise control (ANC) is a technique which can reduce low-frequency noise effectively. The physical effects of an ANC system have been studied by many researchers; however, it is also requested to evaluate ANC systems from the viewpoint of the psychological effects on listeners. On the other hand, general noise assessments have been carried out by the equivalent noise level criteria such as the LAeq. Indeed, the LAeq is a well-designed judgment criterion; however, the evaluation using the LAeq criterion includes an A-weighted filtering. This may cause problems to occur when we treat noise that contains a lot of low-frequency noise components rather than high-frequency components. That is to say, even if the equivalent sound level is small, the low-frequency noise may annoy, and cause harmful effects to, the listener in different ways than the high-frequency noise. The purpose of this paper is to evaluate the effects of an ANC system on human hearing by carrying out a series of experiments. The subjective evaluations revealed the significant effects of ANC in the form of psychological space expressions.
Analysis of psychological effects of low-frequency noise using structural covariance models
Authors: Nakamura Norio , Inukai Yukio
Published: October 2005

It is necessary to discuss comprehensively effects of low-frequency noise (LFN) on different kinds of modalities by extracting multidimensional bases of evaluation in order to clarify the characteristics of human sensation for LFN, because humans have no sense organ singularly specialized for LFN. In previous research, it was confirmed that there were three main factors of psychological evaluation of LFN by the method of factor analysis: loudness, oppression, and vibration. The purpose is to formulate the relation between physical stimuli and psychological evaluation for LFN by introducing structural relationships and using a multivariate technique to access causations and correlations. The method uses psychophysical experiments and statistical analysis. Pure sine-wave stimuli in 22 conditions were radiated with a frequency from 3 to 40 Hz, and sound-pressure level from 70 to 125 dB. Subjects evaluated the stimuli for the 22 psychological indices by psychophysical methods. Structures among the physical stimuli and psychological evaluation are examined by covariance structure analysis. As for the results, structural covariance models are derived which include observed variables of physical stimuli and psychological evaluation for LFN and latent variables of loudness, oppression, and vibration, which show the causal characteristics of sensation for LFN.
Sound quality evaluation of mechanical sound from the viewpoint of the soundscape
Authors: Nakagawa Noritoshi , Sekiguchi Yasuhisa , Takegawa Nobuhide
Published: October 2005

The object of this paper is both to investigate the required sound or preferable sound in each circumstance and to find out the characteristics of the sound. The adequacy of the sound corresponding to the circumstance is investigated. Then the characteristics of the sound are specified. Furthermore, the evaluation of sound quality is attempted on the basis of the concept of the soundscape. The sound from the outdoor unit of an air conditioner is used as an example of mechanical sound, and the pure-tone level is calculated under consideration of the critical bandwidth which is a hearing characteristic of human beings. The results of the pure-tone level are consistent with those of sound quality evaluation by the SD method. Then the usefulness of the evaluation method by use of the pure-tone level is confirmed.
Laser generation and detection of ultrasound: Technology and applications
Authors: Monchalin Jean-Pierre
Published: October 2005

A review of the efforts and recent achievements at the Industrial Materials Institute of the National Research Council of Canada to apply laser generation and optical detection of ultrasound to industrial inspection will be presented. The principles of generation used in the applications developed so far will be outlined. Penetrating light effects, key to generation in a variety of polymers and polymer matrix composites will be discussed. Detection schemes based on the use of a confocal Fabry–Perot in transmission or in reflection will be reviewed, as well as novel approaches based on the use of photorefractive crystals. These approaches include the one based on two-wave mixing, heterodyne interferometry combined with speckle beam cleaning with a double phase conjugation mirror and the photo electromotive force scheme. Two industrial demonstrations of the technology, the inspection of aeronautic parts made of polymer-matrix composite materials (in one case, the inspection was performed directly on an aircraft), and the wall thickness gauging of hot tubes directly on the production line will be presented. The inspection of composite aeronautic parts has been commercially developed and a production inspection system has been installed at a U.S. Air Force maintenance facility by our licensee UltraOptec, Inc.
Velocity measurements in molten materials with the use of laser-generated ultrasound
Authors: Nakano Hidetoshi , Matsuda Youichi , Shin Shoichirou , Nagai Satoshi
Published: October 2005

The temperature dependence of the longitudinal ultrasonic velocity in solid and molten materials was measured by using laser-generated ultrasound. A Q-switched Nd–YAG laser was used for the generation of the ultrasound source. A diode-pumped cw laser or a long-pulse Nd:YAG laser probed the sample, and then the scattered light from the sample was collected into a multimode optical fiber. The light from the fiber was introduced to a Fabry–Perot interferometer to detect the ultrasonic motion. The velocities of solid materials were compared with those by a conventional pulse-echo method at room temperature. These results were in agreement within 0.1%. A transparent cell was used as a container for molten samples. Thus the ultrasound was generated at the boundary between the sample and the container, and detected at the opposite boundary through the cell. The velocities were measured up to 1000 °C, which was limited by the furnace.
Laser generation and detection of elastic waves in graphite/polymer composites
Authors: Caron James N. , Yang Yuqiao , Mehl James B. , Steiner Karl V.
Published: October 2005

Laser-generated ultrasonic waveforms in graphite/polymer composites were detected with a reflection-mode confocal Fabry–Perot (CFP) interferometric system. The CFP was operated in reflection mode for maximum bandwidth (rise times <40 ns). The observed waveform amplitudes are linear in laser power below an ablation threshold. Waveforms at higher power are interpreted as superpositions of thermoelastic (TE) and ablatic (AB) components. The AB wave is formed when the generating laser vaporizes surface material and causes the formation of a hot, glowing plasma. Direct photodetection of the ablation products indicates that the ablation process lasts more than an order of magnitude longer than the generation-laser pulse (5 ns). The ultrasonic waveforms, interpreted with the aid of a theoretical model of the CFP-detection system, are consistent with the assumption of two concurrent generation processes. The maximum amplitude of the ablatic component is reached later than that of the thermoelastic component because of the longer time scale of the ablatic generation.
Acoustic waves generated by phase velocity scanning of laser interference fringes
Authors: Yamanaka Kazushi , Sato Harumichi , Cho Hideo , Takemoto Mikio , Nishino Hideo , Tsukahara Yusuke
Published: October 2005

A method for noncontact and selective generation of surface acoustic waves (SAWs), and bulk acoustic waves (BAWs) is discussed. To generate SAWs, the thermoelastic sources of scanning interference fringes (SIFs) are scanned on an opaque solid surface with a velocity equal to the phase velocity of SAWs, and to generate BAWs the SIFs are scanned at a higher velocity. SAW velocity within the laser beam spot is measured as the ratio of observed frequency of SAWs and wave number of the SIF. The frequency measurement is precise because of the large number of generated carriers, amplitude enhancement of about 10 times, and suppression of other spurious modes (back-propagation SAWs and BAWs). This method was applied to evaluate thin films of SiO2, Si3N4, and porous silicon layers, with a precision around 0.1%. In addition, since a large-amplitude SAW (e.g., 1.4 nm) was realized at high frequencies (e.g., 110 MHz), a large acceleration (up to 109 m/s2) of the surface is achieved, with a moderate peak laser power of 710 kW/cm2. This feature may be attractive for applications in particle manipulation, such as removing dust particles from LSI wafers, in a dry process.
Evaluation of standard defects using surface acoustic waves generated by phase velocity scanning of laser interference fringes
Authors: Sato Harumichi , Nakano Shizuka , Ogiso Hisato , Yamanaka Kazushi
Published: October 2005

In order to maintain the reliability of structural materials such as ceramics, it is important to nondestructively evaluate micrometer-order surface defects that reduce the strength of materials. The standard defects are needed whose size and shape are precisely defined, but only a Vickers and Knoop indentation crack can be used traditionally. However, since indentation cracks are created stochastically, it is difficult to precisely define the size and shape. Alternatively creation of standard defects on Si(100) wafers was attempted by using the focused ion beam (FIB) machining process, and three grooves of 3-μm depth and 50-, 100-, and 200-μm length were made by a 90-nm-diam Ga ion beam on a Si surface. Iodine gas was used for making fine edges. Then these defects were evaluated by using the phase velocity scanning (PVS) method which generates excellently directive surface acoustic waves (SAWs). A 60-MHz SAW generated by the PVS method was used and the distances from detects to the probe of SAW were about 4 mm. The reflection coefficients of 200-, 100-, and 50-μm defects were evaluated to be about 9.6%, 3.5%, and 1%, respectively, and the usefulness of these standard defects was confirmed.
Generation of focused bulk acoustic waves by phase velocity scanning of laser interference fringes
Authors: Nishino Hideo , Nakaso Noritaka , Tsukahara Yusuke , Yamanaka Kazushi
Published: October 2005

In conventional methods of laser ultrasound, the efficiency, the mode selectivity and the directionality were insufficient for precise measurements. In order to overcome these difficulties, the phase velocity scanning (PVS) method [K. Yamanaka et al., Appl. Phys. Lett. 58, 1591 (1991)] of the scanning interference fringe (SIF) approach was proposed, and a single-mode, high-frequency unidirectional ultrasound was efficiently generated [H. Nishino et al., Appl. Phys. Lett. 62, 2036 (1993)]. But in this approach, the amplitude of the bulk acoustic wave (BAW) was not as large as that of the surface acoustic wave, because the interaction length between the fringe and the generated ultrasounds was shorter (Nishino et al., 1993). In this paper, as a novel extension of the SIF approach, a point focusing type of SIF (PFT-SIF) is proposed to focus the BAW with a large amplitude. By intersecting a focused laser beam and a collimated beam with different frequencies on a specimen, a PFT-SIF is formed, which consists of concentric circles scanned into the center with scanning velocities faster for inner circles. Verification is carried out using second-harmonic waves of a Q-switched Nd:YAG laser and an Al specimen, and profiles of focused acoustic fields for 50- to 80-MHz BAWs are studied.
Enhancement of laser-based ultrasonic wave detection through signal processing techniques
Authors: Huber Robert D. , Chinn Diane J. , Candy James V. , Thomas Graham H. , Spicer James B.
Published: October 2005

Laser generation and detection of ultrasonic signals is a technology that expands the applications for ultrasonic nondestructive evaluation. It is a remote, noncontacting method of generating and detecting acoustic energy in materials. Laser-based ultrasonics has been shown to have less sensitivity than traditional ultrasonic testing because the amount of optical energy that can be introduced to a material to generate ultrasonic waves nondestructively is limited by the ablation threshold of the material. In addition, detection sensitivity is limited by the surface conditions of the material as well as the feasible power of the laser used in the interferometer. To increase the signal-to-noise ratio of laser-based acoustic detection, beamforming techniques were applied to modeled and measured data. A thermoacoustic wave propagation model of laser generation and detection was used to simulate data from a bistatic array. The corresponding measured bistatic data set was beamformed in the same manner as the simulated data. Filters derived by matching measured and modeled beamformed data were applied to other measured data sets with good results. These filters can be used to enhance images generated from bistatic laser- based ultrasonic data. [Work performed under auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.]
Progress toward quantitative local ultrasonic measurements
Authors: Quentin Gerard J.
Published: October 2005

The major part of experimental studies in ultrasonics deals with relative measurements of the acoustic field. It means that the absolute value of the ultrasonic pressure or of the acoustic displacements is unknown. Nevertheless, various methods exist for measuring the pressure in a fluid: use of hydrophones, reflection measurements and use of the inverse return principle, calorimetry, ultrasonic balance, etc. In most cases, they are quite difficult to handle, they induce some perturbation of the acoustic field to be measured, and, usually, give only a mean value of this field. The development of laser ultrasonics recently opened new perspectives in this domain. Laser probing of acoustic surface displacements gives very accurate local quantitative measurements. Such probing was limited to interfaces where the laser beam was reflected. This capability was recently extended to measurements of acoustic pressures inside fluids and acoustic dilatation inside solids [X. Jia, Ch. Matteï, and G. Quentin, J. Appl. Phys. 77, 5528–5537 (1995)]. This paper describes the method used and emphasizes the usefulness of such quantitative local ultrasonic measurements and its field of applications.
GHz ultrasonic measurement using a transient reflecting grating method under a surface plasmon resonance condition
Authors: Katayama Kenji , Harata Akira , Sawada Tsuguo , Shen Qing
Published: October 2005

A transient holographic pattern, which is called a transient reflecting grating (TRG), is produced on a solid surface when two pulsed lights are simultaneously irradiated at the same spot of a small size. By using a probe light delayed relative to the above excitation pulses, a time profile of the TRG is observed by changing the delay time of the probe pulse. The signal waveform includes information about generation and relaxation of ultrasonics and heat. Using this technique, a few-GHz ultrasonics were observed for a wide variation of material surfaces [A. Harata et al., Trends Anal. Chem. 14, 504–511 (1995)]. In this report highly sensitive detection of the TRGs utilizing surface plasmon resonance (SPR) is described. Energy deposition efficiency from light into heat was very effective under an SPR condition and the energy absorbed by a surface plasmon polariton (SPP) is concentrated on the solid surface. Utilizing an arrangement of total internal reflection for the SPP excitation, a TRG method about ten times more sensitive could be realized. A new type of SPR-enhanced TRG method is also proposed where the probe beam excites SPPs. The method made it possible to separate ultrasonics and the heat contribution to the TRG signal.
Ultrafast photothermal and photoacoustic measurement of solid/liquid interfaces
Authors: Harata Akira , Hibara Akihide , Sawada Tsuguo
Published: October 2005

Ultrafast photothermal (PT) and photoacoustic (PA) investigation of a metal–solution interface was performed by using subpicosecond time-resolved transient reflectivity (TR) measurement. A polycrystalline platinum film (thickness 30 nm) vapor-deposited on a glass substrate and a polycrystalline platinum disk were investigated in air and in a variety of solutions with and without electrochemical potential control. Transient reflectivity change during and after pulsed laser illumination was measured with a high-precision (<10−6) and high temporal resolution of the pulse width limit (pulse duration 240 fs FWHM). It was found that, in a picosecond time scale, the TR response showed electrolyte dependence as well as electrochemical potential dependence [A. Harata, T. Edo, and T. Sawada, Chem. Phys. Lett. 249, 112–116 (1996)]. These results suggest that interface structure in a molecular scale affects the ultrafast PT/PA phenomena occurring just at the interface. Also observed were ultrahigh-frequency longitudinal acoustic waves ringing in the ultrathin platinum films sandwiched between the glass and the solution. The frequency observed was up to 300 GHz for the sample in air and a strong acoustic damping in the solution was observed.
Ultrafast laser acoustics
Authors: Wright O. B.
Published: October 2005

Acoustic waves generated by ultrashort optical pulses provide a novel approach to materials characterization. Frequencies in the gigahertz to terahertz regime, corresponding to acoustic wavelengths from sub-10 nm to ∼1 μm, can be used to investigate thin layers and nanostructures of commensurate dimensions. Elastic constants, ultrasonic attenuation, and thin film bonding can be probed down to the limit at which continuum acoustics ceases to apply. In addition, the polarity and shape of the generated acoustic pulses provides information on the nonequilibrium photoexcited carrier dynamics. Optical detection methods such as those based on reflectance modulation allow noncontact operation, and further sample characterization can be simultaneously carried out by analyzing signals due to thermal wave propagation. In the present studies, reflectance modulation and beam deflection techniques were used at visible wavelengths to probe the longitudinal optoacoustic generation in thin film and bulk semiconductors and metals. The beam deflection technique allows a direct measure of the acoustic strain pulse shape to be obtained in many cases, allowing simple comparison with the theory of acoustic generation. In metals, for example, the broadening of optically generated acoustic pulses by ultrafast electron diffusion can be confirmed experimentally.
Time-of-flight measurements of high-frequency surface acoustic phonons in silicon
Authors: Ding J. , Photiadis Douglas M. , Barber Zoe
Published: October 2005

Studies of the propagation and attenuation of high-frequency phonons in bulk materials have shown that they are subject to frequency down conversion and scattering due to anharmonic effects and impurities in the crystal. Recently, there have been reports on high-frequency surface phonon propagation concentrating on the issue of phonon focusing. The first time-of-flight measurements are reported of high-frequency surface acoustic phonons in (001) high-quality silicon wafers at low temperatures. Pulsed laser excitation is used for the generation of the high-frequency (≳50 GHz) phonons, and aluminum edge bolometers are used as detectors. The time defined by the fast initial response of the edge bolometer as the position of the optical excitation is varied corresponding to acoustic delays in silicon. The results provide some insights on the propagation and attenuation of high-frequency surface waves, as well as on designing more efficient, high-temperature, high-frequency phonon transducers.
A new method of coherent Rayleigh–Brillouin scattering using frequency-tunable cw lasers
Authors: Tanaka Hajime
Published: October 2005

A new phase-coherent Rayleigh–Brillouin scattering method using frequency-tunable cw lasers has been developed. Spontaneous Brillouin scattering is caused by thermally excited phonons whose phases have no physical meaning because of their random, incoherent nature. Thus only the power spectrum of the density fluctuations is measurable. In principle, however, coherent phonons having phase information can be generated by a scanning interference pattern that is produced by intersecting two laser beams with slightly different frequencies. When the dispersion relation of the phonon is satisfied, coherent phonons are generated resonantly in a sample. This resonance spectrum is physically equivalent to the spontaneous Brillouin spectrum. By a phase-sensitive heterodyne detection of the scattered light due to light-induced coherent phonons, complex Brillouin spectra have been measured for the first time. Since frequency-tunable cw lasers with high phase coherency are used, this method has a high-frequency resolution of ∼1 MHz, irrespective of the phonon frequency. The method has an extremely high sensitivity because of the coherent detection of signals while keeping a much higher frequency resolution than a Fabry–Perot interferometer. It is hoped that the method will be applied for studying the dynamics of acoustic phonons in various condensed matter, superseding a Fabry–Perot interferometer.
Optoacoustics and acousto-optics of penetrating radiation
Authors: Lyamshev Leonid M. , Lyamshev Mikhail L.
Published: October 2005

Excitation of sound in condensed matter by penetrating radiation, i.e., electron, proton and ion beams, synchrotron and laser radiation, x-rays, and single high-energy particles of cosmic rays, is considered. Physical mechanisms are discussed. Theoretical and experimental data on thermoradiational generation of sound are presented. Wave scattering of penetrating radiation by hypersound in condensed matter is considered. Interferention of penetrating radiation waves and construction principles of atomic interferometers including experimental data are discussed. Some applications, i.e., radiation-acoustical microscopy and visualization, acoustical detection of high-energy neutrino and muons, and atomic interferometers applications for measuring of microvibrations, are considered. [Work supported by RFBR.]
Temporal effects in simultaneous and forward masking
Authors: Champlin Craig A.
Published: October 2005

The detectability of a brief tonal signal was measured at various delays relative to the onset of a wideband noise masker. In simultaneous masking, there was complete temporal overlap between the masker and signal. In forward masking, the signal onset followed the masker offset, thus there was no temporal overlap. The overall level (50, 65, or 80 dB SPL) of the masker and the frequency (500 or 2000 Hz) of the signal were varied in conditions of both simultaneous and forward masking. Signal detectability in forward masking always improved as the delay between the masker onset (or offset) and signal onset increased. The change in signal detectability as a function of delay was more complicated in simultaneous masking. The detectability of 2000-Hz signals improved as the delay between the masker onset and signal onset increased. The magnitude of the effect, however, was greatest for mid-level maskers. Curiously, the detectabilityof 500-Hz signals worsened initially and then improved as the delay increased. [Work supported by NIDCD.]