Intensity Probe Research Articles

Sound field separation technique based on single surface measurement using pressure-velocity transducers

The sound field separation technique based on single surface measurement is investigated in this paper. A modified separation formula based on the spatial Fourier transform is presented to overcome the inherent singularity of the current single surface separation technique. However due to the wraparound error associated with fast Fourier transform （FFT）, the accuracy of separation technique based on FFT is not satisfactory and a novel separation method based on the statistically optimized nearfield acoustic holography is proposed to improve the separation. The simulations as well as experiments carried out with the p-u intensity probe produced by Microflown demonstrate the validity of the proposed modified formula and the effectiveness of the new separation method.

Electrical microarrays for highly sensitive detection of multiplex PCR products from biological agents

For the sensitive detection of amplicons derived from diagnostic PCR, a novel electrical low-density microarray is applied and compared to state-of-the-art quantitative real-time PCR. The principle of the electrochemical method and the effective use for analysis are described. Interdigitated array gold electrodes (IDA-E) embedded into a silicon chip are the core technology of the fully automated compact biosensor system, basing on enzyme coupled electrochemical detection. The biointerface is built up with thiol-modified capture oligonucleotides on gold and mediates the specific recognition of hybridised target DNA amplified with uniplex or multiplex PCR. In here we show the potential of the designed electrical microarray to function as an advanced screening method for the parallel detection of a panel of the four pathogens Bacillus anthracis, Yersinia pestis, Francisella tularensis and ortho pox viruses (genus), which are among the most relevant biowarfare agents. PCR products, generated from 10 to 50 gene equivalents, have been detected reproducibly. The experiments with varying pathogen amounts showed the good reliability and the high sensitivity of the method, equivalent to optical real-time PCR detection systems. Without PCR the total assay time amounts to 27 min. The advantage of the combination of multiplex-PCR with electrical microarray detection avoiding intensive PCR probe labelling strategies is illustrated.

Numerical study of sound transmission loss using an indirect boundary element method

The purpose of this study was to simulate transmission loss tests at the acoustic facilities of FG Wilson, Larne, UK. A hemi‐anechoic chamber adjoins a reverberation room via a transmission plug where canopy panel sections are mounted for testing. Boundary element methods in LMS Virtual.Lab are used in conjunction with a baffle model to simulate the test facilities for transmission loss. On one side of this wall the reverberation room is modelled as a diffuse field using a series of defined plane waves, and on the other the hemi‐anechoic chamber is represented as a free field. Experiments were carried out on a steel plate and lead sheet following the ISO 15186 standard for measurement of sound insulation using sound intensity. Source room sound pressure levels were recorded with a microphone, and an intensity probe was used to map the sound intensity field on the receiving side. Transmission loss for a frequency range was calculated as stated in the standard and compared with the results for the computational analysis. Comparison of the computational simulation with the experimental yielded a sufficient agreement.

Vector intensity reconstructions in a volume surrounding a rigid spherical measurement array

An approach is presented that provides a prediction of the vector intensity field throughout a volume exterior to a rigid spherical measurement array consisting of 31 flush mounted microphones. The theory is based on spherical harmonic expansions of the measured field with the radial variation of the near-field pressure obtained using the Greens function with vanishing normal derivative at the rigid sphere surface. Experimental results with rigid spherical arrays of differing radii are presented using multiple incoherent sources. Successful intensity reconstructions are obtained over a volume three times the sphere radius up to a frequency of 1.5 kHz that clearly reveal the locations and levels of the two sources. This volumetric intensity probe is very similar mathematically to one described recently by the author (EGW) that used 50 microphones in an open array. The latter was used successfully inside an aircraft cabin in flight to uncover sources of noise. This work was supported by the US Office of Naval Research and Nittobo Acoustic Engineering Co. Ltd.

Affymetrix Whole-Transcript Human Gene 1.0 ST Array is Highly Concordant with Standard 3′ Expression Arrays

The recently released Affymetrix Human Gene 1.0 ST array has two major differences compared with standard 3' based arrays: (i) it interrogates the entire mRNA transcript, and (ii) it uses DNA targets. To assess the impact of these differences on array performance, we performed a series of comparative hybridizations between the Human Gene 1.0 ST and the Affymetrix HG-U133 Plus 2.0 and the Illumina HumanRef-8 BeadChip arrays. Additionally, both RNA and DNA targets were hybridized on HG-U133 Plus 2.0 arrays. The results show that the overall reproducibility of the Gene 1.0 ST array is best. When looking only at the high intensity probes, the reproducibility of the Gene 1.0 ST array and the Illumina BeadChip array is equally good. Concordance of array results was assessed using different inter-platform mappings. Agreements are best between the two labeling protocols using HG-U133 Plus 2.0 array. The Gene 1.0 ST array is most concordant with the HG-U133 array hybridized with cDNA targets. This may reflect the impact of the target type. Overall, the high degree of correspondence provides strong evidence for the reliability of the Gene 1.0 ST array.

Design and implementation of a three‐dimensional seven microphone vector intensity probe with low and high frequency compensations

A seven microphone vector intensity probe has been designed and implemented in this report with low and high frequency compensations. Measurements from plane wave tube and anechoic chamber are used for overall system calibration with corrected gain and phase mismatch errors. Measured and calculated intensity level from both plane wave tube and anechoic room settings showed close agreement with each other in comparison to separate low and high frequency components of the array. Particle velocity vectors and pressures determined for calculating intensity were also used to calculate sound power and total energy density components of various sources. This microphone array vector intensity probe is then used to explore various sound source identification and localization problems.

Array based measurement of radiated and absorbed sound intensity components

Calibration of energy flow models for cabin environments requires tools able to measure the energy flow between the sub-systems of the models. Here we shall specifically consider the energy flow between acoustic energy in the cabin and vibration energy in the panels. Sound intensity measurement, for example with a two-microphone intensity probe, can provide the total sound intensity at some distance from panels. It cannot resolve, how much of the intensity is due to radiation from the surface and how much is due to absorption of energy from the sound field. And it cannot provide the information right on the panel surface, leading to a degraded resolution. The ability to distinguish between radiated and absorbed intensity is important for energy flow modeling, and for identification of the areas where noise energy enters the cabin. The present paper describes some work done to measure the radiated and absorbed intensity components by the use of a double layer microphone array. Two measurements are performed: A measurement of surface absorption coefficient and an operational measurement. Non-locally reacting surfaces represent a particular challenge, the handling of which will be discussed. Results from both loudspeaker measurements and in-flight measurements will be presented.

Pump-probe spectroscopy in degenerate two-level atoms with arbitrarily strong fields

We study the pump and probe absorption spectra, as a function of the probe detuning, in a degenerate two-level atomic system, for the case where the probe intensity is high enough to affect the pump absorption. The theory is valid for any ${F}_{g}\ensuremath{\rightarrow}{F}_{e}$ alkali-metal transition interacting with an arbitrarily intense pump and probe (with general Rabi frequencies ${\ensuremath{\Omega}}_{1,2}$) which are perpendicularly polarized with either ${\ensuremath{\sigma}}_{\ifmmode\pm\else\textpm\fi{}}$ or $\ensuremath{\pi}$ polarization. We have constructed a computer program that can calculate the spectra without requiring one to write out the Bloch equations explicitly. We show that, when the pump is ${\ensuremath{\sigma}}_{\ifmmode\pm\else\textpm\fi{}}$ polarized and the probe $\ensuremath{\pi}$ polarized, or vice versa, the pump and probe absorptions depend on the Zeeman coherences between the nearest-neighboring ground or excited Zeeman sublevels, whereas when the pump is ${\ensuremath{\sigma}}_{+}$ polarized and the probe ${\ensuremath{\sigma}}_{\ensuremath{-}}$ polarized, or vice versa, the Zeeman coherences that directly determine the absorption are between next-nearest neighbors. We report calculations of the pump and probe absorption spectra for the cycling ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=3$ transition in the ${D}_{2}$ line of $^{87}\text{R}\text{b}$, interacting with a resonant ${\ensuremath{\sigma}}_{+}$-polarized pump and either a $\ensuremath{\pi}$- or a ${\ensuremath{\sigma}}_{\ensuremath{-}}$- polarized probe. The probe and pump absorption spectra are analyzed by considering the contributions that derive from the individual ${m}_{g}\ensuremath{\rightarrow}{m}_{e}$ transitions. We then show how these contributions depend on the ground- and excited-state populations and Zeeman coherences, and investigate the role played by transfer of coherence from the excited to the ground hyperfine state. We show that the pump and probe absorption spectra are mirror images of each other when ${\ensuremath{\Omega}}_{1}\ensuremath{\ge}{\ensuremath{\Omega}}_{2}>\ensuremath{\Gamma}$, and have the same behavior at line center and complementary behavior in the wings, when ${\ensuremath{\Omega}}_{1}\ensuremath{\ge}{\ensuremath{\Omega}}_{2}<\ensuremath{\Gamma}$ ($\ensuremath{\Gamma}$ is the rate of spontaneous decay from ${F}_{e}$ to ${F}_{g}$).

油圧ポンプの発生する固有の脈動源パワーを測定するための標準試験法の開発

This paper is concerned with the experimental determination of an inherent pulsation power level generated by a hydraulic pump, using both the test method originally developed for the measurement of fluid pulsation power in a pipeline and the theoretically derived conversion equation for eliminating the influence of a hydraulic circuit. The suitability of the test procedure as a standard method for assessment of an inherent source pulsation power of a hydraulic pump was confirmed. First, it was found that the pulsation power in a pipeline can be measured using a pressure sensor unit called a “pulsation intensity probe” with the same measurement principle as the conventional sound intensity probe, with good repeatability and with sufficient accuracy for practical usage. Next, the standard test procedure for determining the inherent source pulsation power of a hydraulic pump, which is independent of a hydraulic circuit connected to the pump, from the measurements of the pulsation power in a reference pipe was proposed. Finally, it was verified from the experimental measurements and simulations that this proposed standard test method was very useful for both the absolute and relative assessments of source pulsation power level of a hydraulic pump.

Design and Calibration Tests of an Active Sound Intensity Probe

The paper presents an active sound intensity probe that can be used for sound source localization in standing wave fields. The probe consists of a sound hard tube that is terminated by a loudspeaker and an integrated pair of microphones. The microphones are used to decompose the standing wave field inside the tube into its incident and reflected part. The latter is cancelled by an adaptive controller that calculates proper driving signals for the loudspeaker. If the open end of the actively controlled tube is placed close to a vibrating surface, the radiated sound intensity can be determined by measuring the cross spectral density between the two microphones. A one‐dimensional free field can be realized effectively, as first experiments performed on a simplified test bed have shown. Further tests proved that a prototype of the novel sound intensity probe can be calibrated.

Noise diagnosis using nearfield acoustical holography

This presentation focuses on diagnosis of air- and structure-borne sounds by using nearfield acoustical holography (NAH) with an emphasis on applications of Helmholtz equation least-squares method for various industrial projects. The presentation is structured with strong consideration towards the end result, which is the visualization and quantification of the acoustic field and ranking of relative contributions from individual noise sources. It is emphasized that, in general, this approach does not deal with actual noise control but rather with identifying the areas where such effort may yield the most cost-effective results. Comparison of NAH-based diagnosis with other techniques such as transfer path analysis and an intensity probe is presented, and their relative advantages and disadvantages are discussed. Specific examples of identifications of sound transmission paths into a passenger vehicle compartment, fuselage of an aircraft, and disk brake squeals are presented. The reconstructed acoustic quantities, such as the acoustic pressures and normal surface velocities, are compared with the benchmark results.

Sympathetic cooling of laser-produced doubly charged ions in a few-ion crystal

We present experimental results in which single ${\mathrm{Ca}}^{+}$ ions in a chain of laser cooled ${\mathrm{Ca}}^{+}$ ions are further ionized by means of an intense short pulse laser. The ions are trapped in a linear Paul trap, which is instantaneously loaded by ions from a laser-produced ablation plasma. Due to sympathetic cooling the doubly charged ions are held in place. We study and characterize linear few-ion crystals with mixed charges by applying a radio frequency field, which excites the center of mass (c.m.) and breathing modes of different configurations. From the position shift of laser cooled ions initiated through the higher charge state we can deduce the charge of the nonfluorescing ion. This information might be used as an intensity probe for high intensity lasers.

Characterization of mismatch and high-signal intensity probes associated with Affymetrix genechips

For Affymetrix microarray platforms, gene expression is determined by computing the difference in signal intensities between perfect match (PM) and mismatch (MM) probesets. Although the use of PM is not controversial, MM probesets have been associated with variance and ultimately inaccurate gene expression calls. A principal focus of this study was to investigate the nature of the MM signal intensities and demonstrate its contribution to the experimental results. While most MM intensities were likely associated with random noise, a subset of approximately 20% (99,485) of the MM probes displayed relatively high signal intensities to the corresponding PM probes (MM > PM) in a non-random fashion; 13,440 of these probes demonstrated exceptionally high 'outlier' intensities. About 15,938 PM probes also demonstrated exceptionally high outlier intensities consistently across all hybridizations. About 92% of the MM > PM probes had either a dThymidine (dT) or a dCytidine (dC) at the 13th position of the probe sequence. MM and PM probes displaying extremely high outlier intensities contained high dC rich nucleotides, and low dA contents at other nucleotides positions along the 25mer probe sequence. Differentially expressed genes generated using Genechip Operating System (GCOS) or modified PM-only methods were also examined. Of those candidate genes identified in the PM-only method, 157 of them were designated by GCOS as absent across all datasets and many others contained probes with MM > PM signal intensities. Our data suggests that MM intensity from PM signal can be a major source of error analysis, leading to fewer potentially biologically important candidate genes. Supplementary data are available at Bioinformatics online.

Integrated in silico and biological validation of the blocking effect of Cot-1 DNA on Microarray-CGH

In array-CGH, various factors may act as variables influencing the result of experiments. Among them, Cot-1 DNA, which has been used as a repetitive sequence-blocking agent, may become an artifact-inducing factor in BAC array-CGH. To identify the effect of Cot-1 DNA on Microarray-CGH experiments, Cot-1 DNA was labeled directly and Microarray-CGH experiments were performed. The results confirmed that probes which hybridized more completely with Cot-1 DNA had a higher sequence similarity to the Alu element. Further, in the sex-mismatched Microarray-CGH experiments, the variation and intensity in the fluorescent signal were reduced in the high intensity probe group in which probes were better hybridized with Cot-1 DNA. Otherwise, those of the low intensity probe group showed no alterations regardless of Cot-1 DNA. These results confirmed by in silico methods that Cot-1 DNA could block repetitive sequences in gDNA and probes. In addition, it was confirmed biologically that the blocking effect of Cot-1 DNA could be presented via its repetitive sequences, especially Alu elements. Thus, in contrast to BAC-array CGH, the use of Cot-1 DNA is advantageous in controlling experimental variation in Microarray-CGH.

Design and implementation of a three-dimensional seven microphone acoustic intensity probe for measuring sound properties from various sources

Based on existing theoretical models of multi-dimensional cross-spectral methods for calculating sound pressure and particle velocities, this report has derived and/or extended models of intensity, energy densities, and specific acoustic impedance for seven microphone configurations. Array configuration, spacing, and overall implementation procedure is also outlined in this report. Experimental data has confirmed the validity of the analytical solution for different sound sources in both anechoic and reverberation room environment. Sound sources of different frequency bands [broadband (100 Hz–7 KHz), low (100 Hz–1 KHz), and high (1–7 KHz)] was used separately to compare accuracy and performance of the acoustic probe. Signal processing techniques and software implementation with potential errors and limitations of the system are explained. These would provide a framework for further refinement of instrumentation aspects of the acoustic probe. Potential applications and users of the probe are also described in this report.

Statistically optimized near field acoustic holography using an array of pressure-velocity probes

Statistically optimized near field acoustic holography (SONAH) differs from conventional near field acoustic holography (NAH) by avoiding spatial Fourier transforms; the processing is done directly in the spatial domain. The main advantage of SONAH compared with NAH is that the usual requirement of a measurement aperture that extends well beyond the source can be relaxed. Both NAH and SONAH are based on the assumption that all sources are on one side of the measurement plane whereas the other side is source free. An extension of the SONAH procedure based on measurement with a double layer array of pressure microphones has been suggested. The double layer technique makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of extraneous noise coming from the "wrong" side. It has also recently been demonstrated that there are significant advantages in NAH based on an array of acoustic particle velocity transducers (in a single layer) compared with NAH based on an array of pressure microphones. This investigation combines the two ideas and examines SONAH based on an array of pressure-velocity intensity probes through computer simulations as well as experimentally.

Electro‐vibro‐acoustic Simulation of Linear Vibrations in Ducts

AbstractDue to standing waves the creation of artificial free‐field conditions is required to detect sound sources in weakly damped interiors. Normally sound absorbing material is mounted on the interior walls to eliminate unwanted reflections. In contrast to this time consuming procedure, the present paper describes a local approach that is based on a sound intensity probe with an active free‐field (SIAF). To study the dynamical behavior of a first SIAF‐prototype that consists of two electro‐dynamical loudspeakers mounted at the ends of a duct, an electro‐vibro‐acoustical model was implemented in Matlab/Simulink, and the dynamic behavior of the system was analyzed numerically. The results of these simulations proved that a one‐dimensional free‐field can be produced successfully, if a wave‐separation approach together with an adaptive LMS‐algorithm is applied. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Evaluation of noise intensity level using an eccentric press during the production of metallic closure: Findings according to different positions surrounding the press

This study was performed to evaluate the differences in noise level produced by an eccentric press, during the manufacturing of metallic clo- sures for steel cans. The primary objective of the study was to establish a rank of sound-intensity level and sound-power level as well as the global noise level emitted by this particular press. Ten different areas in the surface surrounding the press were evaluated regarding both the sound power and the sound intensity of each measurement. Each site was measured twice to increase accuracy. The ten areas sampled were sweeping using intensity probe. We have found the surface area to demonstrate the lowest noise level was at S1 and the highest one was at S10 (p value 0.0005). In conclusion, our study demonstrates adequately the global noise level as well as in specific sites, indicating areas requiring special treatment for noise reduction in this environment.

Stress dependence of the near-band-gap cathodoluminescence spectrum of GaN determined by spatially resolved indentation method

A microscopic procedure has been proposed for evaluating the stress dependence of the (room-temperature) cathodoluminescence (CL) excitonic band emitted from the (0001) crystallographic plane of GaN in a field-emission-gun scanning electron microscope. The room-temperature near-band-gap emission (generally referred to as the excitonic band) mainly consisted of a band arising from free exciton (FX). However, an asymmetric morphology was found for the band, which thus needed to be deconvoluted into the main FX band and a shoulder. The spectral location at intensity maximum of the overall excitonic band under stress-free conditions was observed at room temperature at around 365nm. Experimentally measured spectral shifts were precisely retrieved nearby the tip of a Vickers indentation microcrack, while CL intensity probe response functions were collected at different acceleration voltages at a sharp interface between a GaN film and its sapphire substrate. Based on these assessments, the magnitude of the piezospectroscopic coefficient (i.e., the spectral shift rate versus the trace of a biaxial stress tensor) Π=1.35±0.01nm∕GPa of the excitonic (cumulative) band of GaN could be evaluated. This study not only emphasizes the importance of microscopic piezospectroscopic calibration procedures for precise residual stress assessments in GaN-based devices, but also the need of deconvoluting the electron probe for minimizing the error involved with its finite size.

Preliminary Results from the First Monochromated and Aberration Corrected 200-kV Field-Emission Scanning Transmission Electron Microscope

Experimental results from the first monochromated and aberration-corrected scanning transmission electron microscope operated at 200 kV are described. The formation of an electron probe with a diameter of less than 0.2 nm at an energy width significantly under 0.3 eV and its planned application to the chemical analysis of nanometer-scale structures in materials science are described. Both energy and spatial resolution will benefit from this: The monochromator improves the energy resolution for studies of energy loss near edge structures. The Cs corrector allows formation of either a smaller probe for a given beam current or yields, at fixed probe size, an enhanced beam current density using a larger condenser aperture. We also point out another advantage of the combination of both components: Increasing the convergence angle by using larger condenser apertures in an aberration-corrected instrument will enlarge the undesirable chromatic focus spread. This in turn influences spatial resolution. The effect of polychromatic probe tails is proportional to the product of convergence angle, chromatic aberration constant, and energy spread. It can thus be compensated for in our new instrument by decreasing the energy width by the same factor as the beam convergence is increased to form a more intense probe. An alternative in future developments might be hardware correction of the chromatic aberration, which could eliminate the chromatic probe spread completely.