Acoustic holography. LMS Test.Lab. Rev 12A
|
|
- Caitlin Dean
- 6 years ago
- Views:
Transcription
1 Acoustic holography LMS Test.Lab Rev 12A Copyright LMS International 2012
2
3 Table of Contents Chapter 1 Introduction... 5 Chapter Section 2.1 Temporal and spatial frequency... 7 Section 2.2 Time domain... 8 Section 2.3 Spatial domain... 8 Section 2.4 (Back) propagating to other planes Section 2.5 The Wiener filter and the AdHoc window Section 2.6 Derivation of other acoustic quantities Rev 12A 3
4
5 Chapter 1 Introduction Chapter 1 Introduction Acoustic holography allows you to accurately localize noise sources. It therefore helps in both the reduction of unwanted vibro-acoustic noise and optimization of noise levels. It : estimates the acoustic power and the spectral content emitted by the object under examination. maps sound pressure, velocity and intensity on the measurement plane and on all parallel planes. The mapping of these acoustical quantities outside the measurement plane is done through acoustical holography (near field - far field). estimates the acoustic level of the principal sources, including contribution analysis. This document describes the principles of taking acoustic measurements and the subsequent analysis of acoustic holography data, for both stationary and transient measurements. Basic principles In performing acoustic holography, you need to measure cross spectra between a set of reference transducers and the hologram microphones. From these measurements you can derive sound intensity, particle velocity and sound power values. A basic assumption is that you are operating in free field conditions and that the energy flow is coming directly from the source. Measurements need to be taken close to the source. It provides you with an accurate 3D characterization of the sound field and the source with a higher spatial resolution than is possible with conventional intensity measurements. Rev 12A 5
6
7 Chapter 2 In This Chapter Temporal and spatial frequency... 7 Time domain... 8 Spatial domain... 8 (Back) propagating to other planes The Wiener filter and the AdHoc window Derivation of other acoustic quantities The principle of acoustic holography is to decompose the measured pressure field in plane waves, by using a spatial Fourier transform. With the frequency being fixed, we can calculate how each of these plane waves propagates, and by adding them we can find the pressure field on any plane which is parallel to the measurement plane. Consider an acoustic wave. Measuring the pressure on a plane means cutting the wavefronts by the measurement plane: The goal is to determine the whole acoustic wavefront from the known pressure on the measurement plane. Each microphone in the array measures the complex pressure (amplitude and phase). Section 2.1 Temporal and spatial frequency In considering how to do this we will compare the time and the spatial domain. Rev 12A 7
8 Section 2.2 Time domain When considering measurements in the time domain, then the position from the sound source (m) is fixed and we obtain a measure of the pressure variation as a function of time. The transformation from the time to the frequency domain is achieved using the Fourier Transform given below Section 2.3 Spatial domain If we now consider measurements where time is fixed and pressure varies as a function of distance, we can obtain a measure of energy flow. The spatial frequency of this function or wavenumber (k0) is defined as : If we fix the temporal frequency, this means that the acoustic wavelength is fixed too. 8 LMS Test.Lab Acoustic holography
9 The complex pressure as a function of the space is called the pressure image at the specified frequency. Conversion from the spatial domain is also done using a Fourier transform. In Acoustic holography pressure is measured in two dimensions (x and y for example), so a 2-dimensional transformation is performed. where S (kx, ky) is the spatial transform of the measured pressure field to the wavenumber (kx and ky) domain resulting in the 2-D hologram pressure field. A measured pressure (sound) wave with a particular temporal frequency can propagate in a number of directions, so the wavenumber vector (k) will have a number of components. The appearance of these vectors depends on the plane on which you are looking at them. The aim is to find the components of these vectors in the 2 dimensions that define the plane and to do this projections of the vectors in the plane are made. Summation of plane waves Rev 12A 9
10 The spatial Fourier transform implies that a measured pressure field can be considered as a sum of sinusoidal functions. Each of these sinusoidal functions can be understood as the result of cutting the wavefronts of a plane wave by the measurement plane. There is a coincidence between the nodes of the sinusoidal function and the wavefronts. In effect, decomposing the pressure field into a sum of sinusoidal functions means decomposing the real acoustic wave into a sum of plane waves. Whatever the angle of incidence, the spatial periodicity must be greater than the wavelength (l). Propagating and evanescent waves There are two kinds of plane waves : propagating waves - whose level remains the same as they propagate but who undergo a phase shift. evanescent waves - whose level decreases as they propagate. Propagating waves represent the sound field that is propagated away from the near towards the far field. Evanescent waves describe the complex sound field 10 LMS Test.Lab Acoustic holography
11 in the near field of the source. To understand why we must take evanescent plane waves into account, let us consider our decomposition of the pressure field into sinusoidal functions. If the spatial periodicity of a sinusoidal function is shorter than the wavelength, it cannot be the result of cutting a propagating plane wave by the measurement plane : Whatever the direction of the propagating plane wave may be, there is no possible coincidence between the nodes of the sinusoidal function and the wavefronts. Therefore, this sinusoidal function must be understood as the intersection between an evanescent wave (which can have a smaller spatial periodicity than propagating waves) and the measurement plane. A mathematical interpretation of the evanescent waves is based on the value of kz which is the component perpendicular to the measurement directions in the wave number domain. kz can be determined from the wave number k0 and the known values of kx and ky from the transformation. Rev 12A 11
12 kz is real when (the spatial periodicity is greater than the wavelength). This means that the waves lie in the circle defined by the radius w/c in the wave number domain. kz is imaginary outside of this region. When kz is imaginary, the propagation factor becomes a damped exponential function (e-jkz z) meaning that a propagated wave undergoes an amplitude modification while the phase is not changed. Section 2.4 (Back) propagating to other planes Pressure levels at other planes can be found using Raleigh's integral Equation with Dirichlet's Green function : where the Green function Gd can be thought of as the transformation function to transform the sound pressure field from one plane to another. We can use wave domain properties (k) to predict the pressure at a different spatial position (z). The practical computation of Raleigh's equation is: where z' is the measurement plane and z is the position of the required plane. The green function is given by The final step is to perform an inverse transformation back to the temporal domain. 12 LMS Test.Lab Acoustic holography
13 Section 2.5 The Wiener filter and the AdHoc window As mentioned above, evanescent waves undergo a change in amplitude when propagating. Propagating towards the source implies an amplification of the signal that is a function of kz. Evanescent waves that lie far away from the unit circle have a large kz, therefore their amplitude is amplified significantly when propagating to the source. The contribution of these evanescent waves results in an increase of spatial resolution. Note that the inclusion of evanescent waves is only appropriate when propagating towards the source. Propagating away from the source, the evanescent waves decrease so rapidly in amplitude that their contribution to the spatial resolution becomes negligible. However the further away a wave is located from the circle, the less accurate the amplitude estimate becomes so that at a certain point noise is propagated and at that point the propagated image starts to blur. When propagating towards the source, a Wiener filter can be used to include a certain number of evanescent waves to improve the resolution. Taking a higher number of waves taken into account may result in the amplification becoming unstable. This depends on a parameter of the Wiener filter known as the Signal to Noise Ratio (SNR). When the SNR value is greater than 15dB, then the amplification will become unstable as the number of evanescent waves included increases. Using an low SNR value (5dB for example) means that the evanescent waves are taken into account but they are so attenuated that the improvement in resolution is negligible. The default value of 15dB provides the best compromise in terms of resolution and amplification. When the Wiener filter is used, the pressure image needs to be multiplied by a two-dimensional window. As is the case with a single FFT, the observed pressure must be 'periodic' within the observed hologram. If this is not the case, then truncation errors occur as with a single FFT. These truncation errors manifest themselves as ghost sources at the borders of the observed area. Two windows are used: The rectangular window, which does not modify the pressure image. In case of a rectangular window, only propagating waves are included in the calculations resulting in a resolution equivalent to an intensity measurement. The so-called Ad Hoc window For a time signal, the FFT algorithm takes the time signal and duplicates it from minus to plus infinity. If the amplitude of the measured time signal differs Rev 12A 13
14 between the start and the end of the window, a discontinuity occurs during this multiplication introducing an error in the FFT algorithm. This can be corrected using a Hanning window. Holography used a double FFT so the AdHoc window is used, which is basically a two dimensional Hanning window thus removing discontinuities in the both the x and y directions. The one-dimension Ad Hoc window (W) would be: Section 2.6 Derivation of other acoustic quantities If we know how the plane waves propagate, we can calculate the pressure field in any parallel plane, by adding the contributions of all plane waves. This will be correct only if all acoustic sources are on the same side of both planes : Knowing the pressure field on the parallel plane, it is possible to calculate the particle velocity and eventually the intensity on this plane. The particle velocity (V) will be known if the pressure differential can be determined -which is the case with Acoustic holography since the pressure can be measured at r and (r + dr) 14 LMS Test.Lab Acoustic holography
15 Once the pressure and the velocity are known then the intensity is just the product of the two. Rev 12A 15
16
17 ( Index (Back) propagating to other planes 13 A 7 D Derivation of other acoustic quantities 15 I Introduction 5 S Spatial domain 8 T Temporal and spatial frequency 7 The Wiener filter and the AdHoc window 14 Time domain 7 Rev 12A 17
Fan Noise Control by Enclosure Modification
Fan Noise Control by Enclosure Modification Moohyung Lee a, J. Stuart Bolton b, Taewook Yoo c, Hiroto Ido d, Kenichi Seki e a,b,c Ray W. Herrick Laboratories, Purdue University 14 South Intramural Drive,
More informationApplication Note. Brüel & Kjær. Tyre Noise Measurement on a Moving Vehicle. Introduction. by Per Rasmussen and Svend Gade, Brüel & Kjær, Denmark
Application Note Tyre Noise Measurement on a Moving Vehicle by Per Rasmussen and Svend Gade,, Denmar To obtain precise information about the noise radiation from tyres it is desirable to measure with the
More informationTransient, planar, nonlinear acoustical holography for reconstructing acoustic pressure and particle velocity fields a
Denver, Colorado NOISE-CON 013 013 August 6-8 Transient, planar, nonlinear acoustical holography for reconstructing acoustic pressure and particle velocity fields a Yaying Niu * Yong-Joe Kim Noise and
More informationAdvanced Optical Communications Prof. R. K. Shevgaonkar Department of Electrical Engineering Indian Institute of Technology, Bombay
Advanced Optical Communications Prof. R. K. Shevgaonkar Department of Electrical Engineering Indian Institute of Technology, Bombay Lecture No. # 15 Laser - I In the last lecture, we discussed various
More information9.4 Enhancing the SNR of Digitized Signals
9.4 Enhancing the SNR of Digitized Signals stepping and averaging compared to ensemble averaging creating and using Fourier transform digital filters removal of Johnson noise and signal distortion using
More informationAcoustic Quantities. LMS Test.Lab. Rev 12A
Acoustic Quantities LMS Test.Lab Rev 12A Copyright LMS International 2012 Table of Contents Chapter 1 Acoustic quantities... 5 Section 1.1 Sound power (P)... 5 Section 1.2 Sound pressure... 5 Section
More informationFundamentals of the DFT (fft) Algorithms
Fundamentals of the DFT (fft) Algorithms D. Sundararajan November 6, 9 Contents 1 The PM DIF DFT Algorithm 1.1 Half-wave symmetry of periodic waveforms.............. 1. The DFT definition and the half-wave
More informationNonstationary filters, pseudodifferential operators, and their inverses
Nonstationary filters, pseudodifferential operators, and their inverses Gary F. Margrave and Robert J. Ferguson ABSTRACT An inversion scheme for nonstationary filters is presented and explored. Nonstationary
More informationLight Propagation in Free Space
Intro Light Propagation in Free Space Helmholtz Equation 1-D Propagation Plane waves Plane wave propagation Light Propagation in Free Space 3-D Propagation Spherical Waves Huygen s Principle Each point
More informationPlate mode identification using modal analysis based on microphone array measurements
Plate mode identification using modal analysis based on microphone array measurements A.L. van Velsen, E.M.T. Moers, I. Lopez Arteaga, H. Nijmeijer Department mechanical engineering, Eindhoven University
More informationNIH Public Access Author Manuscript Ultrason Imaging. Author manuscript; available in PMC 2013 November 21.
NIH Public Access Author Manuscript Published in final edited form as: Ultrason Imaging. 2012 October ; 34(4):. doi:10.1177/0161734612463847. Rapid Transient Pressure Field Computations in the Nearfield
More informationFILTERING IN THE FREQUENCY DOMAIN
1 FILTERING IN THE FREQUENCY DOMAIN Lecture 4 Spatial Vs Frequency domain 2 Spatial Domain (I) Normal image space Changes in pixel positions correspond to changes in the scene Distances in I correspond
More informationHARMONIC WAVELET TRANSFORM SIGNAL DECOMPOSITION AND MODIFIED GROUP DELAY FOR IMPROVED WIGNER- VILLE DISTRIBUTION
HARMONIC WAVELET TRANSFORM SIGNAL DECOMPOSITION AND MODIFIED GROUP DELAY FOR IMPROVED WIGNER- VILLE DISTRIBUTION IEEE 004. All rights reserved. This paper was published in Proceedings of International
More informationThe Continuous-time Fourier
The Continuous-time Fourier Transform Rui Wang, Assistant professor Dept. of Information and Communication Tongji University it Email: ruiwang@tongji.edu.cn Outline Representation of Aperiodic signals:
More informationIntroduction to Acoustics. Phil Joseph
Introduction to Acoustics Phil Joseph INTRODUCTION TO ACOUSTICS Sound and Noise Sound waves Frequency, wavelength and wavespeed Point sources Sound power and intensity Wave reflection Standing waves Measures
More informationIntroduction to Seismology Spring 2008
MIT OpenCourseWare http://ocw.mit.edu 12.510 Introduction to Seismology Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 12.510 Introduction
More information674 JVE INTERNATIONAL LTD. JOURNAL OF VIBROENGINEERING. MAR 2015, VOLUME 17, ISSUE 2. ISSN
1545. The improved separation method of coherent sources with two measurement surfaces based on statistically optimized near-field acoustical holography Jin Mao 1, Zhongming Xu 2, Zhifei Zhang 3, Yansong
More informationLet us consider a typical Michelson interferometer, where a broadband source is used for illumination (Fig. 1a).
7.1. Low-Coherence Interferometry (LCI) Let us consider a typical Michelson interferometer, where a broadband source is used for illumination (Fig. 1a). The light is split by the beam splitter (BS) and
More information1. Calculation of the DFT
ELE E4810: Digital Signal Processing Topic 10: The Fast Fourier Transform 1. Calculation of the DFT. The Fast Fourier Transform algorithm 3. Short-Time Fourier Transform 1 1. Calculation of the DFT! Filter
More informationChapter 16 Holography
Chapter 16 Holography Virtually all recording devices for light respond to light intensity. Problem: How to record, and then later reconstruct both the amplitude and phase of an optical wave. [This question
More informationUniversity of Bristol - Explore Bristol Research. Link to publication record in Explore Bristol Research PDF-document.
Dobra, T., Lawrie, A., & Dalziel, S. B. (2016). Nonlinear Interactions of Two Incident Internal Waves. 1-8. Paper presented at VIIIth International Symposium on Stratified Flows, San Diego, United States.
More informationSEISMIC WAVE PROPAGATION. Lecture 2: Fourier Analysis
SEISMIC WAVE PROPAGATION Lecture 2: Fourier Analysis Fourier Series & Fourier Transforms Fourier Series Review of trigonometric identities Analysing the square wave Fourier Transform Transforms of some
More informationAPPLICATION OF MVDR BEAMFORMING TO SPHERICAL ARRAYS
AMBISONICS SYMPOSIUM 29 June 2-27, Graz APPLICATION OF MVDR BEAMFORMING TO SPHERICAL ARRAYS Anton Schlesinger 1, Marinus M. Boone 2 1 University of Technology Delft, The Netherlands (a.schlesinger@tudelft.nl)
More informationDevelopment of an Energy-Based Nearfield Acoustic Holography System
Brigham Young University BYU ScholarsArchive All Theses and Dissertations 2005-05-23 Development of an Energy-Based Nearfield Acoustic Holography System Michael C. Harris Brigham Young University - Provo
More informationSound Generation from Vortex Sheet Instability
Sound Generation from Vortex Sheet Instability Hongbin Ju Department of Mathematics Florida State University, Tallahassee, FL.3306 www.aeroacoustics.info Please send comments to: hju@math.fsu.edu When
More information3.1 The Plane Mirror Resonator 3.2 The Spherical Mirror Resonator 3.3 Gaussian modes and resonance frequencies 3.4 The Unstable Resonator
Quantum Electronics Laser Physics Chapter 3 The Optical Resonator 3.1 The Plane Mirror Resonator 3. The Spherical Mirror Resonator 3.3 Gaussian modes and resonance frequencies 3.4 The Unstable Resonator
More informationSound transmission loss of windows on high speed trains
Sound transmission loss of windows on high speed trains Yumei Zhang 1,, Xinbiao Xiao 1, David Thompson, Giacomo Squicciarini, Zefeng Wen 1, Zhihui Li 1, Yue Wu 1 1 State Key Laboratory of Traction Power,
More informationSPEECH ANALYSIS AND SYNTHESIS
16 Chapter 2 SPEECH ANALYSIS AND SYNTHESIS 2.1 INTRODUCTION: Speech signal analysis is used to characterize the spectral information of an input speech signal. Speech signal analysis [52-53] techniques
More informationMULTI-RESOLUTION SIGNAL DECOMPOSITION WITH TIME-DOMAIN SPECTROGRAM FACTORIZATION. Hirokazu Kameoka
MULTI-RESOLUTION SIGNAL DECOMPOSITION WITH TIME-DOMAIN SPECTROGRAM FACTORIZATION Hiroazu Kameoa The University of Toyo / Nippon Telegraph and Telephone Corporation ABSTRACT This paper proposes a novel
More informationExperimental feasibility of in-duct sound source reconstruction
Acoustics 8 Paris Experimental feasibility of in-duct sound source reconstruction T. Bravo and C. Maury Université de Technologie de Compiègne Centre de Recherche Royallieu BP2529 625 Compiègne France
More informationA wavenumber approach to characterizing the diffuse field conditions in reverberation rooms
PROCEEDINGS of the 22 nd International Congress on Acoustics Isotropy and Diffuseness in Room Acoustics: Paper ICA2016-578 A wavenumber approach to characterizing the diffuse field conditions in reverberation
More informationThe Analysis of Data Sequences in the Time and Frequency Domains 1
The Analysis of Data Sequences in the Time and Frequency Domains 1 D. E. Smylie 1 c D. E. Smylie, 2004. Contents 1 Time Domain Data Sequences 1 1.1 Discrete, Equispaced Data Sequences....... 1 1.2 Power
More informationEmpirical Mean and Variance!
Global Image Properties! Global image properties refer to an image as a whole rather than components. Computation of global image properties is often required for image enhancement, preceding image analysis.!
More informationChapter 11 Vibrations and Waves
Chapter 11 Vibrations and Waves 11-1 Simple Harmonic Motion If an object vibrates or oscillates back and forth over the same path, each cycle taking the same amount of time, the motion is called periodic.
More informationStructure of Biological Materials
ELEC ENG 3BA3: Structure of Biological Materials Notes for Lecture #19 Monday, November 22, 2010 6.5 Nuclear medicine imaging Nuclear imaging produces images of the distribution of radiopharmaceuticals
More informationModeling II Linear Stability Analysis and Wave Equa9ons
Modeling II Linear Stability Analysis and Wave Equa9ons Nondimensional Equa9ons From previous lecture, we have a system of nondimensional PDEs: (21.1) (21.2) (21.3) where here the * sign has been dropped
More informationIMAGE ENHANCEMENT II (CONVOLUTION)
MOTIVATION Recorded images often exhibit problems such as: blurry noisy Image enhancement aims to improve visual quality Cosmetic processing Usually empirical techniques, with ad hoc parameters ( whatever
More information5. LIGHT MICROSCOPY Abbe s theory of imaging
5. LIGHT MICROSCOPY. We use Fourier optics to describe coherent image formation, imaging obtained by illuminating the specimen with spatially coherent light. We define resolution, contrast, and phase-sensitive
More informationVibrational velocity estimation by means of PNAH
Vibrational velocity estimation by means of PNAH S. Potgieter DCT 2009.064 Bachelor Final Project Supervisor: dr.ir. I. Lopez Arteaga Technische Universiteit Eindhoven Department Mechanical Engineering
More information10. OPTICAL COHERENCE TOMOGRAPHY
1. OPTICAL COHERENCE TOMOGRAPHY Optical coherence tomography (OCT) is a label-free (intrinsic contrast) technique that enables 3D imaging of tissues. The principle of its operation relies on low-coherence
More informationElectromagnetic fields and waves
Electromagnetic fields and waves Maxwell s rainbow Outline Maxwell s equations Plane waves Pulses and group velocity Polarization of light Transmission and reflection at an interface Macroscopic Maxwell
More informationA study on regularization parameter choice in Near-field Acoustical Holography
Acoustics 8 Paris A study on regularization parameter choice in Near-field Acoustical Holography J. Gomes a and P.C. Hansen b a Brüel & Kjær Sound and Vibration Measurement A/S, Skodsborgvej 37, DK-285
More informationOSE801 Engineering System Identification. Lecture 09: Computing Impulse and Frequency Response Functions
OSE801 Engineering System Identification Lecture 09: Computing Impulse and Frequency Response Functions 1 Extracting Impulse and Frequency Response Functions In the preceding sections, signal processing
More informationVibration Testing. an excitation source a device to measure the response a digital signal processor to analyze the system response
Vibration Testing For vibration testing, you need an excitation source a device to measure the response a digital signal processor to analyze the system response i) Excitation sources Typically either
More information1/27/2010. With this method, all filed variables are separated into. from the basic state: Assumptions 1: : the basic state variables must
Lecture 5: Waves in Atmosphere Perturbation Method With this method, all filed variables are separated into two parts: (a) a basic state part and (b) a deviation from the basic state: Perturbation Method
More informationMEASUREMENT OF INPUT IMPEDANCE OF AN ACOUSTIC BORE WITH APPLICATION TO BORE RECONSTRUCTION
MEASUREMENT OF INPUT IMPEDANCE OF AN ACOUSTIC BORE WITH APPLICATION TO BORE RECONSTRUCTION Maarten van Walstijn Murray Campbell David Sharp Department of Physics and Astronomy, University of Edinburgh,
More informationComputer Vision. Filtering in the Frequency Domain
Computer Vision Filtering in the Frequency Domain Filippo Bergamasco (filippo.bergamasco@unive.it) http://www.dais.unive.it/~bergamasco DAIS, Ca Foscari University of Venice Academic year 2016/2017 Introduction
More informationExam tomorrow on Chapter 15, 16, and 17 (Oscilla;ons and Waves 1 &2)
Exam tomorrow on Chapter 15, 16, and 17 (Oscilla;ons and Waves 1 &2) What to study: Quiz 6 Homework problems for Chapters 15 & 16 Material indicated in the following review slides Other Specific things:
More informationBIOSIGNAL PROCESSING. Hee Chan Kim, Ph.D. Department of Biomedical Engineering College of Medicine Seoul National University
BIOSIGNAL PROCESSING Hee Chan Kim, Ph.D. Department of Biomedical Engineering College of Medicine Seoul National University INTRODUCTION Biosignals (biological signals) : space, time, or space-time records
More informationVibration Testing. Typically either instrumented hammers or shakers are used.
Vibration Testing Vibration Testing Equipment For vibration testing, you need an excitation source a device to measure the response a digital signal processor to analyze the system response Excitation
More informationPressure Normal Derivative Extraction for Arbitrarly Shaped Surfaces Endrias G. Asgedom,Okwudili Chuks Orji, Walter Söllner, PGS
Pressure Normal Derivative Extraction for Arbitrarly Shaped Surfaces Endrias G. Asgedom,Okwudili Chuks Orji, Walter Söllner, PGS Downloaded 9// to... Redistribution subject to SEG license or copyright;
More informationIMPROVEMENTS IN ACTIVE NOISE CONTROL OF HELICOPTER NOISE IN A MOCK CABIN ABSTRACT
IMPROVEMENTS IN ACTIVE NOISE CONTROL OF HELICOPTER NOISE IN A MOCK CABIN Jared K. Thomas Brigham Young University Department of Mechanical Engineering ABSTRACT The application of active noise control (ANC)
More informationArray Antennas. Chapter 6
Chapter 6 Array Antennas An array antenna is a group of antenna elements with excitations coordinated in some way to achieve desired properties for the combined radiation pattern. When designing an array
More informationFIBER OPTICS. Prof. R.K. Shevgaonkar. Department of Electrical Engineering. Indian Institute of Technology, Bombay. Lecture: 15. Optical Sources-LASER
FIBER OPTICS Prof. R.K. Shevgaonkar Department of Electrical Engineering Indian Institute of Technology, Bombay Lecture: 15 Optical Sources-LASER Fiber Optics, Prof. R.K. Shevgaonkar, Dept. of Electrical
More informationChapter 4 Discrete Fourier Transform (DFT) And Signal Spectrum
Chapter 4 Discrete Fourier Transform (DFT) And Signal Spectrum CEN352, DR. Nassim Ammour, King Saud University 1 Fourier Transform History Born 21 March 1768 ( Auxerre ). Died 16 May 1830 ( Paris ) French
More informationPhysical Acoustics. Hearing is the result of a complex interaction of physics, physiology, perception and cognition.
Physical Acoustics Hearing, auditory perception, or audition is the ability to perceive sound by detecting vibrations, changes in the pressure of the surrounding medium through time, through an organ such
More informationNoise source localization on washing machines by conformal array technique and near field acoustic holography
Proceedings of the IMAC-XXVIII February 1 4, 2010, Jacksonville, Florida USA 2010 Society for Experimental Mechanics Inc. Noise source localization on washing machines by conformal array technique and
More informationSNR Calculation and Spectral Estimation [S&T Appendix A]
SR Calculation and Spectral Estimation [S&T Appendix A] or, How not to make a mess of an FFT Make sure the input is located in an FFT bin 1 Window the data! A Hann window works well. Compute the FFT 3
More informationLecture Notes 5: Multiresolution Analysis
Optimization-based data analysis Fall 2017 Lecture Notes 5: Multiresolution Analysis 1 Frames A frame is a generalization of an orthonormal basis. The inner products between the vectors in a frame and
More informationThe influence of Boundary Conditions on Sound Insulation
The influence of Boundary Conditions on Sound Insulation Master s Thesis in the Master s programme in Sound and Vibration CHRISTOFFER JANCO Department of Civil and Environmental Engineering Division of
More informationContents Preface iii 1 Origins and Manifestations of Speckle 2 Random Phasor Sums 3 First-Order Statistical Properties
Contents Preface iii 1 Origins and Manifestations of Speckle 1 1.1 General Background............................. 1 1.2 Intuitive Explanation of the Cause of Speckle................ 2 1.3 Some Mathematical
More informationA technique based on the equivalent source method for measuring the surface impedance and reflection coefficient of a locally reacting material
A technique based on the equivalent source method for measuring the surface impedance and reflection coefficient of a locally reacting material Yong-Bin ZHANG 1 ; Wang-Lin LIN; Chuan-Xing BI 1 Hefei University
More informationTHEORY AND DESIGN OF HIGH ORDER SOUND FIELD MICROPHONES USING SPHERICAL MICROPHONE ARRAY
THEORY AND DESIGN OF HIGH ORDER SOUND FIELD MICROPHONES USING SPHERICAL MICROPHONE ARRAY Thushara D. Abhayapala, Department of Engineering, FEIT & Department of Telecom Eng, RSISE The Australian National
More informationAcoustic MIMO Signal Processing
Yiteng Huang Jacob Benesty Jingdong Chen Acoustic MIMO Signal Processing With 71 Figures Ö Springer Contents 1 Introduction 1 1.1 Acoustic MIMO Signal Processing 1 1.2 Organization of the Book 4 Part I
More informationAttenuation and dispersion
Attenuation and dispersion! Mechanisms: Absorption (inelastic); Scattering (elastic).! Mathematical descriptions! Measurement! Frequency dependence! Dispersion, its relation to attenuation Reading: Sheriff
More informationMicrowave-induced thermoacoustic tomography using multi-sector scanning
Microwave-induced thermoacoustic tomography using multi-sector scanning Minghua Xu, Geng Ku, and Lihong V. Wang a) Optical Imaging Laboratory, Biomedical Engineering Program, Texas A&M University, 3120
More informationA METHOD FOR NONLINEAR SYSTEM CLASSIFICATION IN THE TIME-FREQUENCY PLANE IN PRESENCE OF FRACTAL NOISE. Lorenzo Galleani, Letizia Lo Presti
A METHOD FOR NONLINEAR SYSTEM CLASSIFICATION IN THE TIME-FREQUENCY PLANE IN PRESENCE OF FRACTAL NOISE Lorenzo Galleani, Letizia Lo Presti Dipartimento di Elettronica, Politecnico di Torino, Corso Duca
More informationChirp Transform for FFT
Chirp Transform for FFT Since the FFT is an implementation of the DFT, it provides a frequency resolution of 2π/N, where N is the length of the input sequence. If this resolution is not sufficient in a
More informationULTRASONIC INSPECTION OF TITANIUM ALLOYS WITH A TIME REVERSAL
ULTRASONIC INSPECTION OF TITANIUM ALLOYS WITH A TIME REVERSAL MIRROR Najet Chakroun Veronique Miette' Mathias Fink Franyois Wu Gerard Mangenet Lionel Beffy 'Laboratoire Ondes et Acoustique Espci, University
More information6.003: Signal Processing
6.003: Signal Processing Discrete Fourier Transform Discrete Fourier Transform (DFT) Relations to Discrete-Time Fourier Transform (DTFT) Relations to Discrete-Time Fourier Series (DTFS) October 16, 2018
More informationUNIVERSITY OF SOUTHAMPTON
UNIVERSITY OF SOUTHAMPTON PHYS2023W1 SEMESTER 1 EXAMINATION 2016-2017 WAVE PHYSICS Duration: 120 MINS (2 hours) This paper contains 9 questions. Answers to Section A and Section B must be in separate answer
More informationHolographic measuring techniques in acoustics
Holographic measuring techniques in acoustics Ferenc Márki and Fülöp Augusztinovicz Budapest University of Technology and Economics, Dept. of Telecommunications H-1111 Budapest, Sztoczek u., ferko@hit.bme.hu
More informationOPAC102. The Acoustic Wave Equation
OPAC102 The Acoustic Wave Equation Acoustic waves in fluid Acoustic waves constitute one kind of pressure fluctuation that can exist in a compressible fluid. The restoring forces responsible for propagating
More informationFourier transforms and convolution
Fourier transforms and convolution (without the agonizing pain) CS/CME/BioE/Biophys/BMI 279 Oct. 26, 2017 Ron Dror 1 Outline Why do we care? Fourier transforms Writing functions as sums of sinusoids The
More informationAnalysis of Finite Wordlength Effects
Analysis of Finite Wordlength Effects Ideally, the system parameters along with the signal variables have infinite precision taing any value between and In practice, they can tae only discrete values within
More informationISO 354 INTERNATIONAL STANDARD. Acoustics Measurement of sound absorption in a reverberation room
INTERNATIONAL STANDARD ISO 354 Second edition 2003-05-15 Acoustics Measurement of sound absorption in a reverberation room Acoustique Mesurage de l'absorption acoustique en salle réverbérante Reference
More information2.161 Signal Processing: Continuous and Discrete Fall 2008
IT OpenCourseWare http://ocw.mit.edu 2.161 Signal Processing: Continuous and Discrete all 2008 or information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. assachusetts
More information7.2.1 Seismic waves. Waves in a mass- spring system
7..1 Seismic waves Waves in a mass- spring system Acoustic waves in a liquid or gas Seismic waves in a solid Surface waves Wavefronts, rays and geometrical attenuation Amplitude and energy Waves in a mass-
More informationOptimisation using measured Green s function for improving spatial coherence in acoustic measurements
Ultrasonics 42 (2004) 205 212 www.elsevier.com/locate/ultras Optimisation using measured Green s function for improving spatial coherence in acoustic measurements Matthew Clark *, Steve D. Sharples, Mike
More informationFourier series. XE31EO2 - Pavel Máša. Electrical Circuits 2 Lecture1. XE31EO2 - Pavel Máša - Fourier Series
Fourier series Electrical Circuits Lecture - Fourier Series Filtr RLC defibrillator MOTIVATION WHAT WE CAN'T EXPLAIN YET Source voltage rectangular waveform Resistor voltage sinusoidal waveform - Fourier
More informationMusic 206: Digital Waveguides
Music 206: Digital Waveguides Tamara Smyth, trsmyth@ucsd.edu Department of Music, University of California, San Diego (UCSD) January 22, 2016 1 Motion for a Wave The 1-dimensional digital waveguide model
More informationEnvironmental Effects and Control of Noise Lecture 2
Noise, Vibration, Harshness Sound Quality Research Group NVH-SQ Group University of Windsor 92-455 Environmental Effects and Control of Noise Copyright 2015 Colin Novak Copyright 2015 by Colin Novak. All
More informationMICROPHONE ARRAY METHOD FOR THE CHARACTERIZATION OF ROTATING SOUND SOURCES IN AXIAL FANS
MICROPHONE ARRAY METHOD FOR THE CHARACTERIZATION OF ROTATING SOUND SOURCES IN AXIAL FANS Gert HEROLD, Ennes SARRADJ Brandenburg University of Technology, Chair of Technical Acoustics, Siemens-Halske-Ring
More informationL6: Short-time Fourier analysis and synthesis
L6: Short-time Fourier analysis and synthesis Overview Analysis: Fourier-transform view Analysis: filtering view Synthesis: filter bank summation (FBS) method Synthesis: overlap-add (OLA) method STFT magnitude
More informationCorrelator I. Basics. Chapter Introduction. 8.2 Digitization Sampling. D. Anish Roshi
Chapter 8 Correlator I. Basics D. Anish Roshi 8.1 Introduction A radio interferometer measures the mutual coherence function of the electric field due to a given source brightness distribution in the sky.
More informationChem Homework Set Answers
Chem 310 th 4 Homework Set Answers 1. Cyclohexanone has a strong infrared absorption peak at a wavelength of 5.86 µm. (a) Convert the wavelength to wavenumber.!6!1 8* = 1/8 = (1/5.86 µm)(1 µm/10 m)(1 m/100
More information(Refer Slide Time: 01:30)
Networks and Systems Prof V.G K.Murti Department of Electrical Engineering Indian Institute of Technology, Madras Lecture - 11 Fourier Series (5) Continuing our discussion of Fourier series today, we will
More informationAn Fir-Filter Example: Hanning Filter
An Fir-Filter Example: Hanning Filter Josef Goette Bern University of Applied Sciences, Biel Institute of Human Centered Engineering - microlab Josef.Goette@bfh.ch February 7, 2018 Contents 1 Mathematical
More informationTHE ACOUSTIC IMPEDANCE MEASUREMNET SYSTEM USING TWO MICROPHONES
P-7 THE ACOUSTIC IMPEDANCE MEASUREMNET SYSTEM USING TWO MICROPHONES RYU, YUNSEON BRUEL & KJAER SOUND & VIBRATION MEASUREMENT A/S SKODSBORGVEJ 307 NAERUM 2850 DENMARK TEL : +45 77 41 23 87 FAX : +45 77
More informationSound Waves. Sound waves are longitudinal waves traveling through a medium Sound waves are produced from vibrating objects.
Sound Waves Sound waves are longitudinal waves traveling through a medium Sound waves are produced from vibrating objects Introduction Sound Waves: Molecular View When sound travels through a medium, there
More informationSound radiation and sound insulation
11.1 Sound radiation and sound insulation We actually do not need this chapter You have learned everything you need to know: When waves propagating from one medium to the next it is the change of impedance
More informationE : Lecture 1 Introduction
E85.2607: Lecture 1 Introduction 1 Administrivia 2 DSP review 3 Fun with Matlab E85.2607: Lecture 1 Introduction 2010-01-21 1 / 24 Course overview Advanced Digital Signal Theory Design, analysis, and implementation
More informationElec4621 Advanced Digital Signal Processing Chapter 11: Time-Frequency Analysis
Elec461 Advanced Digital Signal Processing Chapter 11: Time-Frequency Analysis Dr. D. S. Taubman May 3, 011 In this last chapter of your notes, we are interested in the problem of nding the instantaneous
More information2.161 Signal Processing: Continuous and Discrete Fall 2008
IT OpenCourseWare http://ocw.mit.edu 2.6 Signal Processing: Continuous and Discrete Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. ASSACHUSETTS
More informationThe Acoustical Channel the Transfer Function of Water Pipes
The Acoustical Channel the Transfer Function of Water Pipes Supervisor Prof Werner Henkel Student Behrouz Touri 1 Introduction Because of the sever exponentially attenuation of the electro magnetic waves
More informationElectronics Prof. D C Dube Department of Physics Indian Institute of Technology Delhi
Electronics Prof. D C Dube Department of Physics Indian Institute of Technology Delhi Module No. 07 Differential and Operational Amplifiers Lecture No. 39 Summing, Scaling and Averaging Amplifiers (Refer
More informationAccurate Fourier Analysis for Circuit Simulators
Accurate Fourier Analysis for Circuit Simulators Kenneth S. Kundert Cadence Design Systems (Based on Presentation to CICC 94) Abstract A new approach to Fourier analysis within the context of circuit simulation
More informationChapter 14: Wave Motion Tuesday April 7 th
Chapter 14: Wave Motion Tuesday April 7 th Wave superposition Spatial interference Temporal interference (beating) Standing waves and resonance Sources of musical sound Doppler effect Sonic boom Examples,
More informationFourier Analysis. 19th October 2015
Fourier Analysis Hilary Weller 19th October 2015 This is brief introduction to Fourier analysis and how it is used in atmospheric and oceanic science, for: Analysing data (eg climate
More informationChirp images in 2-D fractional Fourier transform domain. Presenter: Ming-Feng Lu Beijing Institute of Technology July 20, 2016
Chirp images in -D fractional Fourier transform domain Presenter: Ming-Feng Lu lumingfeng@bit.edu.cn Beijing Institute of Technology July 0, 016 目录 Introduction of chirp images Chirp images in FRFT domain
More information