| 1. |
- Arnela, Marc, et al.
(författare)
-
Finite element generation of vowel sounds using dynamic complex three-dimensional vocal tracts
- 2016
-
Ingår i: Proceedings of the 23rd international congress on sound and vibration. - : INT INST ACOUSTICS & VIBRATION. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- Three-dimensional (3D) numerical simulations of the vocal tract acoustics require very detailed vocal tract geometries in order to generate good quality vowel sounds. These geometries are typically obtained from Magnetic Resonance Imaging (MRI), from which a volumetric representation of the complex vocal tract shape is obtained. Static vowel sounds can then be generated using a finite element code, which simulates the propagation of acoustic waves through the vocal tract when a given train of glottal pulses is introduced at the glottal cross-section. A more challenging problem to solve is that of generating dynamic vowel sounds. On the one hand, the acoustic wave equation has to be solved in a computational domain with moving boundaries, which entails some numerical difficulties. On the other hand, the finite element meshes where acoustic wave propagation is computed have to move according to the dynamics of these very complex vocal tract shapes. In this work this problem is addressed. First, the acoustic wave equation in mixed form is expressed in an Arbitrary Lagrangian-Eulerian (ALE) framework to account for the vocal tract wall motion. This equation is numerically solved using a stabilized finite element approach. Second, the dynamic 3D vocal tract geometry is approximated by a finite set of cross-sections with complex shape. The time-evolution of these cross-sections is used to move the boundary nodes of the finite element meshes, while inner nodes are computed through diffusion. Some dynamic vowel sounds are presented as numerical examples.
|
|
| 2. |
- Bodén, Hans, et al.
(författare)
-
Effect of flow direction on acoustic liner impedance measurement results
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- The last twenty years have seen a large development in inverse techniques for the determination of liner impedance under grazing flow conditions, so called impedance eduction techniques. This paper contributes to a continuing effort to gain confidence in results obtained under different acoustical excitation configurations. Many test rigs for determination of liner impedance including the effect of mean flow use plane wave excitation on the upstream side of the liner. Some studies has compared the result for downstream acoustic excitation and found that different acoustic impedances are obtained in the two cases. It is still an open question if this result is due to the application of the Ingard-Myers boundary condition or to other errors or flaws in the measurements. This paper collects data available in the literature to see if the trend of obtaining different results for upstream and downstream excitation is persistent.
|
|
| 3. |
- Chen, Lin Strobin, et al.
(författare)
-
ACOUSTIC SCATTERING BEHAVIOR OF A 2D FLAME WITH HEAT EXCHANGER IN CROSS-FLOW
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : International Institute of Acoustics and Vibrations. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- In practical heat production systems, premixed flames with cold heat exchanger in cross-flow is a widely used configuration. Self-excited thermoacoustic instabilities often occur in such systems. A practical way to predict the presence of the instabilities is the network model approach. In the present study, the configuration flame - heat exchanger is analyzed numerically. We first analyze the system as a network of segregated elements. Based on the resulting acoustic scattering matrix, the role of the heat exchanger as an amplifier of the flame resonant frequencies will be discussed. Then, results from the 1D network modeling are compared to results of compressible numerical simulations, performed for several distances between flame and heat exchanger. Finally, the limits to the validity of the segregated network model approach are discussed.
|
|
| 4. |
- Goubert, Luc, et al.
(författare)
-
Development of the ultra low noise poroelastic road surface : The findings of the persuade project
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- A poroelastic road surface (PERS) consists of rubber granulates and stone aggregates, bound with an elastic resin, such as polyurethane. It does not contain bitumen. Thanks to its elasticity, porosity and texture, it is capable of yielding an unequalled noise reduction, typically 8 - 12 dB(A) with respect to reference dense asphalt concrete. Although already invented in 1979, some persistent problems, the most important being as durability, prevented the use of it for noise abatement.In 2009 the six year EU funded project PERSUADE started, aiming to develop a highly noise reducing, safe and affordable PERS with an acceptable durability. The approach of the PERSUADE consortium was at the same time holistic (all aspects of PERS were studied) and step-wise. It started with laboratory testing of mixes and adhesion to the sub layer. Then small scale pilot test tracks were constructed on parking lots and consequently full scale test tracks on real roads. An extensive monitoring program extracted as much as possible information from the test tracks.Many other relevant aspects, such as cost-benefit, fire safety, toxicity, sustainability, etc were thoroughly studied. This contribution outlines all the findings of the project and makes clear how one go further with this technology.
|
|
| 5. |
- Göthberg, Mattias, et al.
(författare)
-
Efficient multi channel vibration measuremen : systematic approach
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics. - : INT INST ACOUSTICS & VIBRATION. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- In Atlas Copco a wide range of machines is produced from surface drill rigs, exploration drill rigs, underground drill rigs both for mining and construction to underground loader and haulers for mines. Recently new rock excavation methods have developed in cooperation with large mining companies. The machines are produced in low volume and often customized although having a modular approach. Time for validation is limited due to machines available for test are planned for customer delivery. It is on regular basis needed to validate and investigate vibrational behavior of installations as power packs and drivelines to get loads for simulation, identify resonances, operational deflection shapes, and vibration and stress levels for life length estimations under operational conditions. The time for a 40-180 Channel measurement is now down the range of 1-3 days. To reduce the time it takes to perform measurement a systematic approach has been taken that includes mainly three areas. First the Bookkeeping of all information and data needed for the analysis and reporting is input before or during the measurement. Systematic Approach of how to setup sensors, handle cable and equipment, planning and measurement. This includes practical examples of how to. Finally it is very important to take steps to assure Quality early in the measurement and also avoiding disturbances in the sensor path. There will be practical examples of important disturbances to look out for and quality check to perform. It should also be noted that the measurements is regular measured in mines or start up halls under rpm sweeps or/and operating conditions of the machines.
|
|
| 6. |
- Kodakadath Premachandran, Rammohan, et al.
(författare)
-
Comparison of Spectral Properties of the Vibration Signal and Line Pressure Signal of DTH Drill
- 2016
-
Ingår i: 23rd International Congress on Sound and Vibration 2016 (ICSV 23): From Ancient to Modern Acoustics, Publisher: Curran Associates, Inc.. - : Curran Associates, Inc.. - 9781510827165 - 9789609922623
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Quantifying and Monitoring of drilling performance are becoming exceedingly important in the case of Down the Hole drilling. Various economic, environmental and safety constraints are driving the drilling process to become more efficient. To make a robust system that would enable the performance/condition monitoring of the drilling, we must understand how different properties like different line pressure etc. respond to various drilling conditions and what information can they provide regarding the Drilling Performance. A comparison of different properties like spectral properties, of the vibration signals and Pressure signals under known conditions would enable better understanding of the drilling system and the physics behind the process. A comparison is made between the Spectral properties of the vibrational signals obtained from remote locations on the drill rig and pressure signals that provide the feed and holdback forces to the drill string and a correlation between their characteristics and patterns under good and bad drilling conditions have been made. A simplified model of the system is simulated and results are compared with the patterns obtained from analyzing the Vibration signals.
|
|
| 7. |
- Källström, Elisabeth, et al.
(författare)
-
Identification of vibration properties of heavy duty machine driveline parts as a base for adequate condition monitoring: Axle
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : INT INST ACOUSTICS & VIBRATION. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- With increasing complexities in the heavy duty construction equipment, early fault detection of certain components in the machine becomes more and more challenging due to too many fault code generated when a failure occurs. The axle is one of such component. The axle transfers driving torque from the transmission to the wheels and axle failure may result in costly downtime of construction equipment. To reduce service cost and to improve uptime, adequate condition monitoring based on sensor data from the axle is considered. Vibration is measured on the axle. Analysis of the data has been carried out using adequate signal processing methods. The results indicate that the vibration properties of the axle are relevant for early fault detection of the axle. In this way; the health of the axle may be continuously monitored on-board using the vibration information and if the axle health starts to degrade a service and/or repair may be scheduled well in advance of a potential axle failure and in that way the downtime of a machine may be reduced.
|
|
| 8. |
- Källström, Elisabeth, et al.
(författare)
-
Identification of vibration properties of heavy duty machine driveline parts as a base for adequate condition monitoring: Torque converter
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : INT INST ACOUSTICS & VIBRATION. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- Improving uptime is paramount in the heavy duty construction equipment business. Failure ofcritical components in the heavy duty machine may lead to unnecessary stops and expensive downtime. The torque converter, a complex omponent of the driveline, transmits and multiplies torque from the engine to the gearbox, and its failure may not only lead to the machine standing still but may also lead to damage of other parts of the automatic transmission. For adequate condition monitoring of the torque converter, different sensor data are measured on a construction equipment machine during controlled driving sessions. Vibration has been measured on the torque converter. An initial investigation of the vibration measured on the torque converter has been carried out to identify its vibration properties in order to enable its health monitoring to prevent failure. Initial signal analysis of the data have been carried out using Order Power Spectrum and Order Modulation Spectrum methods. The results indicate that the torque converter vibration properties contain information relevant for early fault detection.
|
|
| 9. |
- Peerlings, Luck, et al.
(författare)
-
Experimental uncertainty analysis of impedance measurements
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : International Institute of Acoustics and Vibrations. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- The study of the interaction between acoustics and flow has a long history, and has attracted many scholars. Consequently the major contributors to acoustic-flow interaction are known and improvements made on models to describe the various interactions, give a relative small impact to the overall effect. To validate these new models, experiments have to be more precise and accurate, otherwise no valid statement can be made if the measurements are agreeing with the improved models. The flow-acoustic interaction is commonly measured using impedance tubes through which a flow flows. In this paper, a linear uncertainty analysis is presented to determine the precision of the obtained impedance results. Such kind of analysis has been already reported in literature, but in this paper, the analysis has been expanded to include more uncertain variables and the method is investigated to show the limitations of such an analysis. As an application of the analysis, the measurement of a known impedance without flow has been analyzed, revealing the presence of bias errors in the measurement setup.
|
|
| 10. |
- Surendran, A., et al.
(författare)
-
Aeroacoustic response of an array of tubes with bias-flow
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : International Institute of Acoustics and Vibrations. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- Heat exchanger tube bundles, consisting of tube arrays in cross flows, are vital in the efficient working of power generation systems. If sound propagates through these bundles, it can lead to resonance or acoustic attenuation, and thereby affecting the working of the power generation unit. Therefore, it is important to study the aeroacoustics of tube rows. The aim of the present work is to experimentally validate the quasi-steady compressible model developed to study the aeroa-coustic response of an array of tubes with bias flow. In order to accomplish this, the array of tubes is approximated by a geometry consisting of two half cylinders separated by a gap and having a bias flow through the gap. Firstly, the case with no flow is considered and the experimental results for the reflection and transmission coefficients are compared against the analytical expressions developed by Huang and Heckl (Huang and Heckl, 1993, Acustica 78, 191-200). Then the cases with flow are considered. A quasi-steady subsonic compressible model is developed to predict the reflection and transmission coefficients, valid for low Strouhal numbers, with the additional assumption of small Helmholtz number and low Mach numbers. This model is validated against the experimental results for the transmission and reflection coefficients. A two-port multi-microphone measurement technique is used to obtain the pressure data and a subsequent wave decomposition is utilised to extract the transmission and reflection coefficients. The results show good agreement with theory for various Mach numbers, in the low Strouhal number regime.
|
|
| 11. |
- Temiz, M. A., et al.
(författare)
-
Numerical estimation of the absorption coefficient of flexible micro-perforated plates in an impedance tube
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - : International Institute of Acoustics and Vibrations. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- In this study, we numerically model a vibro-acoustic system consisting of a flexible micro-perforated plate (f-MPP) and an acoustic medium. Combined with a back-cavity, micro-perforated plates are considered as a promising noise control technology due to their tunable, wide-band sound absorption characteristics and robust performance. An MPP consists of a plate with uniformly distributed perforations whose diameters are in the order of a millimeter. These perforations are small enough to dissipate the acoustic perturbations due to the viscous effects caused by the presence of the Stokes layers. When the plate is rigid, the sound dissipation mechanism for a specific frequency bandwidth is determined by the perforation diameter, plate thickness, plate porosity and the back cavity depth. Yet, when the plate is flexible, additional absorption peaks, which cannot be determined by the parameters mentioned before, are observed in the measurements. This phenomenon is due to the vibro-acoustic coupling of the flexible plate and the acoustic medium. To model the vibro-acoustic system numerically, we couple two 3D cylindrical acoustic mediums, i.e. incident and back cavity regions, with a flexible plate consisting of shell elements. The perforations are separately located on the plate as independent transfer admittance elements with impedance values obtained from existing models. The system is disturbed with a plane wave excitation and the assessment of the model is done by comparing the calculated absorption coefficient with the experimental results from the literature. In the future, we plan to investigate the effect of perforation positions with the help of the model built in this study.
|
|
| 12. |
- Weng, C., et al.
(författare)
-
Effectofmean flow shear on sound propagation in uniform circular ducts
- 2016
-
Ingår i: ICSV 2016 - 23rd International Congress on Sound and Vibration. - 9789609922623
-
Konferensbidrag (refereegranskat)abstract
- Acoustic measurements based on multi-port models are commonly applied to investigate generation or scattering behaviors of in-duct components (turbocharger, mufflers, etc.) in confined flows. These multi-port models usually require information about the sound attenuations and the mode shapes of the cut-on higher-order acoustic modes in the rigid-wall duct. Although there are well-established models for determining theses parameters, most of the models are based on a uniform-flow assumption which neglects the refraction effects of the mean flow shear on the sound propagation. To understand the importance of the refraction effects, a numerical investigation is conducted to study the influence of the transverse mean-velocity gradients on the viscothermal damping and mode shapes of both the fundamental and higher-order modes in uniform circular ducts with rigid walls. The investigation is based on the linearized Navier-Stokes equations (LNSE) formulated in the frequency domain and several prescribed shear mean-velocity profiles (one turbulent boundary layer profile and two exponential-then-uniform profiles). The numerical results are compared with a model based on the uniform-flow assumption.
|
|
