Sound Probe Research Articles

Effect of Insert Porosity on Combustion Instability in a Lean Premixed Combustor Analyzed by a Proper Orthogonal Decomposition-Based Phase Reconstruction Technique

Abstract Lean premixed (LPM) combustion is very effective at mitigating emissions but is vulnerable to strong thermoacoustic instabilities. A porous insert in the shape of an annular ring placed at the dump plane of the combustor has been proven to be an effective passive technique for mitigating these instabilities across a wide range of operating conditions. However, it is unclear if the change results from the insert geometry or porosity of the insert. In this study, swirl-stabilized LPM combustion is investigated for three configurations—without any insert, with a porous insert, and with a geometrically similar solid insert. Acoustics, flow, and heat release rate behavior of the three test geometries are investigated using diagnostics including dynamic pressure and acoustic probes, particle image velocimetry (PIV), and OH* chemiluminescence (OH*CL) imaging. Synchronized measurements at a fixed equivalence ratio were acquired at 40 kHz using sound probes and at 3.5 kHz using PIV and OH*CL. Results include time-series and spectral measurements of pressure, velocity, and OH*CL, and mode analysis by proper orthogonal decomposition (POD). In addition, the dynamics of the instability are investigated by high-resolution phase reconstructions of velocity and OH*CL data using a novel implementation of POD introduced in this work. Results show two different instability modes: a longitudinal instability for the solid insert case and a helical, precessing vortex driven instability for the no insert case. In both cases, the flow field and heat release rate oscillations are coupled to produce the instability. No such coupling or oscillations is observed for the porous insert case. These results ascertain the unique capabilities of the porous insert in protecting against instability from different, simultaneous driving mechanisms and demonstrate that the insert porosity and flow dynamics associated with it are the primary mitigating factors.

Differential Scanning Calorimetry as a New Method to Evaluate the Effectiveness of Rejuvenating Agents in Bitumens

To date, few methods allow distinguishing a fluxing effect of an additive for bitumen from a regenerating effect. This research aims at identifying a method to accurately establish whether an oxidized bitumen has been regenerated or has simply been fluxed by a softener. Oxidized bitumens, simulating the aging process that results in road pavement lifetime, were prepared by the Rolling thin film oven test (RTFOT) procedure for 225 min and the Pressure Aging Vessel (PAV) procedure. Their asphaltene parts were extracted and analyzed by calorimetry (Differential Scanning Calorimetry DSC), and the results were compared with the presence and absence of a fluxing agent and real rejuvenators. The self-consistent results showed that the thermal properties of the asphaltene fractions is a sound probe to monitor the effect of rejuvenation clearly distinguishable from the mere fluxing effect. This preliminary study might allow the creation of standard protocols capable of identifying a priori the rejuvenating effect of an additive in the future. Furthermore, given the widespread use of calorimetry for the characterization, it tends to become a widely accessible and useful tool for this purpose in material characterization laboratories.

Contextual cueing facilitation arises early in the time course of visual search: An investigation with the `speed-accuracy tradeoff task.

Visual search is expedited in a spatial context encountered repeatedly. A much-debated question is how early the facilitation by contextual memory arises. The current study examined the possibility of the facilitation of early attentional processing by constructing a descriptive model of the time course of visual search and its facilitation by contextual cueing. Participants in this experiment engaged in a speed-accuracy tradeoff (SAT) task after learning the spatial contexts in a standard visual search task in which they searched for a rotated T target among Ls. In the SAT task, they were required to search for the target and respond immediately when a sound probe was presented, even if they did not find or identify the target when the inter-stimulus interval between the search display and the probe varied from 40 ms to 2,000 ms. Participants completed two blocks of the SAT task, in which they searched in learned and new contexts. The results of the SAT procedure showed that responses were more accurate in repeated contexts than in new contexts, even when only a brief period of time elapsed after presenting the search display (> 90 ms). We conducted an analysis of the time course of contextual-cueing effects with Bayesian hierarchical modeling, which demonstrated that the rate of increase in accuracy was higher for the repeated than for the new contexts. These findings suggest that early attentional processing is enhanced by learning the contexts, and this enhancement arises very early in the time course of the visual search.

Dual-function water-level/well-depth meter

Depth to water table and depth to well bottom are crucial measurements for hydrological and hydrogeological investigations. Available water level meters, commonly called well sounders, measure only depth to water table. For depth to well bottom, hydrogeologists hustle to sense when the sounder tip touches the well bottom to get a rough estimation of the depth to well bottom. This introduces significant amount of error and is extremely hard to apply in deep wells. Some recently introduced sounders have a special probe for measuring well bottom depth. However, those sounders are tedious to use and lack the required durability because of the need to roll up the entire cable and to swap probes for every measurement. Water-Level/Well-Depth (WL/WD) meter is novel dual-function well sounder that is capable of measuring both water table level and depth to well bottom using a single probe easily and precisely. The sounder probe is designed in a way that allows sensing both water table and depth to well bottom efficiently. The reel, cable and electronic circuit are also modified in a way that allows for switching between water level and well bottom depth measurements with a push of a button. Field tests conducted on the new WL/WB meter clearly show its efficiency, precision and durability.

Improving accuracy of elephant localization using sound probes

Localization of elephants in the vicinity of villages is an important issue in mitigating human-elephant conflict. This paper proposes an inexpensive, effective and non-invasive framework that employs a sound probe technique with an acoustic sensor network to localize elephants. Incorporation of probes in our sensor network eliminates the requirement to explicitly measure temperature and wind velocity for accurate determination of sound velocity. A sensor network has been built and experiments performed by replaying recorded elephant sounds under three different environmental conditions. The results overall show that the system is capable of providing remarkable accuracy under distinct wind and temperature conditions. An identical experimental set up was used to localize wild elephants in Sri Lanka. Our approach enabled localization of wild elephants at a distance of over 500m from the sensors to within 30m, providing adequate time for the villages to take appropriate safety measures.

Fracture identification based on remote detection acoustic reflection logging

Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture–borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture–borehole distance, fracture aperture, and dip angle on fracture identification.

Sound based indoor and outdoor environment detection for seamless positioning handover

Abstract In this paper, we propose a sound-based indoor and outdoor environment detection method to realize seamless positioning handover for in-and-outdoor integrated positioning systems. The proposed method uses a special chirp sound probe which is propagated by a speaker of a mobile device and collected back through a microphone of the device. The indoor and outdoor environments are detected by analyzing the reverberation patterns of the retrieved probe. When we tested the proposed method at 46 indoor and outdoor locations, roughly 95% detection accuracy was achieved.

Identification of Aircraft Noise During Acoustic Monitoring by Using 3D Sound Probes

Identification of Aircraft Noise During Acoustic Monitoring by Using 3D Sound Probes

Non Contact Vibration Measurements on Parabolic Surface Antenna

Abstract In this paper it is present a non contact method for 3D measurements on parabolic surface antenna. In order to obtain modal parameters and modal shapes of a parabolic surface antenna a Microflown USP (Ultimate Sound Probe) is used. Microflown sensors are close to antenna and can be used for the non contact measurement of the normal component of the structural velocity.

Photocatalytic hydrogen evolution on new mesoporous material Bi2S3/Y-zeolite

The novel semi conducting configuration n-Bi2S3/Y-zeolite is elaborated by exchange reaction between H/Y-zeolite and Bi3+. The precipitation of Bi2S3 is achieved with thiourea, and activated by ultra sound probe at a frequency of 20 kHz for 60 min. X-ray diffraction and Raman spectroscopy confirm the formation of Bi2S3 which crystallizes in an orthorhombic symmetry. The scanning electron microscopy (SEM) shows uniform and rough surface with fine Bi2S3 crystallites. The specific surface area (SBET = 87.82 m2 g−1) is ∼seven times greater than that of Bi2S3 (9.57 m2 g−1) prepared under the same conditions. The Mott–Schottky characteristic gives a flat band potential of 0.465 VNHE. The electrical conductivity of Bi2S3 is correlated to the optical gap (Eg = 1.40 eV) and photo-electrochemical characterization to establish the energetic diagram of the hetero-system Bi2S3/Y-zeolite/KOH solution. The latter predicts a spontaneous hydrogen evolution upon visible light. An enhancement of twice with respect to Bi2S3 is obtained in presence of S2O32− as holes scavenger. The best performance (292 μmol H2 (g catalyst)−1 h−1) occurs at pH ∼13.1 with a light-to-chemical energy yield of 0.12%.

Effect of occlusion and landmarks on single object tracking during disrupted viewing

(blue) and motion path of tracked object (red). This participants uses discrete eye-movements to accurately track the square up until sound probe (orange) when eyes stabilize on same position until tap response is made (about 1 second later). This sustained gaze-response may serve as a “place-holder” to help keep track of the position of the tracked object. Effect of Occlusion and Landmarks on Single Object Tracking During Disrupted Viewing Meriam Naqvi1 ,2, Kevin Zish1, Ronald Planer1,3, Deborah Aks1, Zenon W. Pylyshyn1 Rutgers Center for Cognitive Science1, Rutgers Department of Biological Sciences2, Rutgers Department of Philosophy3

Measurement of Vertical Temperature Distribution Using a Single Pair of Loudspeaker and Microphone with Acoustic Reflection

It is important to maintain an adequate indoor temperature for comfortable working conditions, improvement of the rate of production of farm goods grown in greenhouses, and for saving energy. Thus, it is necessary to measure the temperature distribution to realize efficient air-conditioning systems. However, we have to use many conventional instruments to measure the temperature distribution. We proposed a measurement system for vertical temperature distribution using a single pair of loudspeaker (SP) and microphone (MIC), and acoustic reflectors. This system consists of SP, MIC, and multiple acoustic reflectors, and it can be used to determine the temperature distribution from the mean temperature of the area bounded by two reflectors. In experiments, the vertical temperature distribution was measured using five sound probes in a large facility every 20 s for 24 h. From the results of this experiment, it was verified that this system can be used to measure the vertical temperature distribution from the mean temperature of each area bounded by two reflectors. This system could be used to measure the change in the temperature distribution over time. We constructed a simple system to measure the vertical temperature distribution.

Air Temperature Distribution Measurement Using Asynchronous-Type Sound Probe

In conventional temperature measurement using a sound probe, the operation beginnings of two acoustic sensors must be completely synchronized to measure time of flight (TOF), tf, because the precision of synchronization determines TOF measurement accuracy. A wireless local area network (LAN) is convenient for constructing a sensing grid; however, it causes a fluctuation in the delay of millisecond order. Therefore, it cannot provide sufficient precision for synchronizing acoustic sensors. In previous studies, synchronization was achieved by a trigger line using a coaxial cable; however, the cable reduces the flexibility of a wireless sensing grid especially in larger-scale measurement. In this study, an asynchronous-type sound probe is devised to compensate for the effect of the delay of millisecond order caused by the network. The validity of the probe was examined, and the air temperature distribution was measured using this means. A matrix method is employed to obtain the distribution. Similar results were observed using both asynchronous-type sound probes and thermocouples. This shows the validity of the use of a sensing grid with an asynchronous-type sound probe for temperature distribution measurement even if the trigger line is omitted.

Ultrasonic Airflow Meter in Greenhouse Using Acoustic Reflection against Wall

In this paper, we described an ultrasonic airflow meter in a greenhouse using an acoustic reflection against a wall. The ultrasonic airflow meter is available for measuring the spatial mean wind velocity and direction, which consists of two sound probes and the wall of the greenhouse. Use of sound probes has advantage that the airflow accumulated along sound paths from a loudspeaker to a microphone is obtained in contrast to point measurements. The wind velocity and direction are calculated from time of flights (TOFs) of direct and reflected signals. The wind velocity and direction were measured in a greenhouse of 7.2 m × 29.0 m under factitious winds generated from two large electric fans located at the one side of the greenhouse. In addition, we detected air convection generated from two pairs of fans. These were measured every 20 seconds for 120 minutes. Regarding the measurement; by the proposed airflow meter and a reference; by a conventional one, their mean wind velocities were 0.12 and 0.15 (m/s), respectively. The presented airflow meter using the acoustic reflection against the wall is convenient to measure the wind velocity and direction in large‐size facilities such as the greenhouse.

Real time sound field visualization in the near field, far field and at absorbing surfaces

The Microflown is a small sensor that is capable of measuring the acoustic particle velocity. In combination with a small pressure microphone it is possible to measure the complete sound field. If the sound field close to an acoustic material is measured it make sense to measure the particle velocity normal to the surface and the sound pressure. With this, the acoustic impedance and absorption can be measured in real time, and with a high spatial resolution. If the sound field of a sound radiating object is measured, the sound field can be obtained directly. Three applications include: direct acoustic camera, that is the real time display of the sound field (velocity, pressure, intensity). Holography that is the pressure, velocity reconstruction on the surface based on the measured sound field (and other places). And cabin interior noise mapping, that is the visualization of the interior noise perceived on a certain location. With three dimensional sound probes (sound pressure and particle velocity in three dimensions), sources in the free field can be found for both bearings as distance. Most recent developments are presented.

Two-Axis Anemometer with Acoustic Reflector Using Single Pair of Loudspeaker and Microphone

In this paper, we describe a two-axis anemometer with an acoustic reflector using a single pair of a loudspeaker (SP) and a microphone (MIC). The two-axis anemometer proposed in this study consists of a SP, a MIC and an acoustic reflector, which form a right-angled isosceles triangle. This anemometer can measure spatial mean wind velocity and direction by calculating each wind component along the coordinate axis defined in each propagation path; this anemometer is targeted for use in air-conditioning systems of high efficiency. The sound probe consists of a SP, a MIC, an acoustic reflector and each propagation path. By using the acoustic reflector, an additional sound path becomes available. In this case, the time of flight (TOF) can be measured using a single SP–MIC pair because of the difference in TOF between direct and reflected waves. Some experiments were carried out in a wind tunnel to measure wind velocity and direction at various wind velocities. The sound probe is placed on a turntable in a wind tunnel. Although the actual wind direction is constant, the apparent direction relative to the sound probe can be changed by rotating a turntable. The measured wind velocities and directions in the experiments showed only small changes with the wind direction change. The feasibility and accuracy of the proposed two-axis anemometer for wind velocity and direction measurements were confirmed.

Influence of the sweeping direction of the primaries f1 and f2 in the assessment of distortion product otoacoustic emissions (DPOAEs) fine structure

It was studied if the sweeping direction of the primaries f1 and f2 influences fine structure measurements of the 2f1−f2 distortion product otoacoustic emission (DPOAE). Two different methodologies named DPOAE5ASC (ascending sweep) and DPOAE5DES (descending sweep) were implemented with the commercial system ILO96. Both methods perform fine structure measurements in the same frequency range (1.4–6 kHz) with L1/L2=65/45 dB, f2/f1=1.22 and 0.7 s averaging time per primary presented. DPOAE fine structures were measured in the right ear of 14 normal‐hearing subjects with both methods in a balanced experiment and without refitting the sound probe. Results showed that the two methods are highly repeatable and able to detect fine structures even in subjects with low S/N. However, when DPOAE5ASC measurements are compared with DPOAE5DES, fine structures appear shifted and the level contour is altered. A minor level difference was inadvertently induced due to differences in the level calibration procedure of the two...

Microflown based sound pressure microphone suitable for harsh environments

There are several cases where a sound field reconstruction or prediction is required under harsh conditions such as high temperature, humidity or chemical attack. A regular pressure microphone will not last long under these conditions. Electret based pressure microphones stop working well above 70 degrees centigrade and other type of pressure microphones often operate with a built in amplifier that does not function above 120 degrees centigrade. The functionality of a MEMS based Microflown acoustic particle velocity sensor in air lies in the use of two heated platinum wires that are resistant to high temperatures and chemical attack. The wires are supported by silicon that has no other function than provide support. A pressure microphone is made based upon the Microflown principle by putting it in the opening of an enclosure. In this paper a silicon and platinum based sound probe for harsh environments is created, combining particle velocity and pressure measurements in a harsh environment. Use of this sensor is possible up to 250 degrees centigrade, in humid and under most chemical environments. The probe realization as well as calibration measurements are presented.

Ultrasonic Fog Detector for Greenhouse with Evaporative Fog Cooling System

To improve the spray control of evaporative fog cooling systems in greenhouses, we propose an ultrasonic fog detector. Conventional evaporative fog cooling systems have not been equipped with fog detectors and spray control has not been sufficient. The effect of fog on the amplitude and phase of ultrasonic waves between a loudspeaker and a microphone was electrically measured by quadrature detection. From the laboratory experiment using a sound probe with a 300 mm base line, the phase of the propagation characteristics showed marked lowering only while fog exists along the propagation path. In a greenhouse experiment using a sound probe with a 740 mm base line, similar results are obtained. In these experiments, the existence or nonexistence of fog was detected by the sound probe at the frequency of 40 kHz.

Error Analysis for Micrometeorological Measurements Using Bidirectional Sound Probe with Long Baseline in Wind Fields

We estimated the measurement errors caused by the errors in time of flight (TOF) and length of the baseline, in meteorological measurement using bidirectional sound probes with a long baseline. In addition, we simulated the measurement in three types of spatial wind distribution, using simple ray tracing. TOFs and the length of the sound ray were calculated for the three wind distributions. The calculated values of air temperature and wind velocity component derived from the TOFs and the length of the ray, were compared with their line-averaged values along the baseline. The results show good agreement. The errors were approximately -0.7°C for the air temperature and approximately -0.01 m/s for the wind component even in wind fields where a 20 m/s wind exists on the baseline. This indicated that the bidirectional-sound probe with a long baseline could satisfactorily carry out micrometeorological measurement in wind fields using conventional calculations.