Change search
Refine search result
12 51 - 74 of 74
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Molin, Nils-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Zipser, Lothar
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Optical methods of today for visualizing sound fields in musical acoustics2004In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 90, no 4, p. 618-628Article in journal (Refereed)
    Abstract [en]

    Pictures that demonstrate physical phenomena are important in science, so also in musical acoustics. In optics, interference, diffraction and polarization phenomena are for instance often pictured in text books. Phase contrast methods are used in microscopy to visualize transparent objects. Such methods have numerous applications in medicine and biology. Shadowgraph, schlieren and different kinds of classical interferometry setups are used in fluid mechanics to study laminar flow, turbulence, convection, subsonic and supersonic flow, shock waves etc. Propagating sound fields often accompany supersonic flow and shock waves. Also transparent object fields like sound and temperature fields can be pictured using optical measuring methods. Merits of these methods are that they are contactless, nondisturbing and wholefield methods. In this paper, some modern optical methods are presented that has the sensitivity and spatial resolution needed to visualize and measure sound fields in musical acoustics. They are computerized, all-electronic methods that present pictures but also give quantitative measures. Harmonic vibrations, standing waves, repetitive sequences and transient wave propagation will be addressed. TV holography, pulsed TV holography and scanning laser Doppler vibrometry (LDV), or scanning vibrometry will be discussed. Speckle photography and correlation methods like digital speckle photography (DSP) and particle image velocimetry (PIV) will also be shortly presented

  • 52. Olofsson, Kenneth
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Kyösti, Anders
    A new method to detect anisotropy and local variations in paper1991In: TAPPI Journal, ISSN 0734-1415, Vol. 74, no 3, p. 195-200Article in journal (Refereed)
  • 53. Olofsson, Kenneth
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Kyösti, Anders
    Mechanical properties of corrugated board as studied by holographic interferometry1992In: TAPPI Journal, ISSN 0734-1415, Vol. 75, no 10, p. 86-93Article in journal (Refereed)
  • 54. Olofsson, Kenneth
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Kyösti, Anders
    Mechanical Properties of Paper and Corrugated Board studied by Pulsed Holographic Interferometry1992In: 1992 Paper Physics Seminar: June 8-11, 1992, Dipoli Conference Center, Otaniemi, Finland / [ed] Kaarlo Niskanen; Sirkka-Liisa Kaukanen, Espoo: KCL , 1992Conference paper (Refereed)
  • 55. Olsson, Erik
    et al.
    Molin, Nils-Erik
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Zipser, Lothar
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Franke, Heinz
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Scattered ultrasound fields measured by scanning laser vibrometry2003In: Optical Measurement Systems for Industrial Inspection III: 23 - 26 June 2003, Munich, Germany / [ed] Wolfgang Osten, Bellingham, Wash.: SPIE - International Society for Optical Engineering, 2003, p. 717-727Conference paper (Refereed)
    Abstract [en]

    A scanning laser Doppler vibrometer is used to make quantitative measurements of 2D ultrasound fields in air. The laser light traverses the measurement volume to and from a rigid reflector and determines the velocity of the change in optical path length, which with constant geometry only depends on the changes in index of refraction. Assuming adiabatic conditions, the refractive index rate is proportional to the sound pressure rate and quantitative measures of the sound field are possible to achieve. The emitted or scattered ultrasound being measured origins from a source or object outside the recording area. Using phase conjugation the sound field is then digitally reconstructed outside the recording area, and the reconstructed phase and intensity reveals the location of the source or object. The combination of several such reconstructions of ultrasound fields of different wavelengths, so called wavelength scanning, provides an intensity map that very accurately gives the position of the source. This opens many new possibilities to study hidden or unknown sound sources or scattering objects

  • 56.
    Rossing, Thomas D.
    et al.
    Northern Illinois University.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Runnemalm, Anna
    Luleå tekniska universitet.
    Modal analysis of violin bodies viewed as three-dimensional structures2003In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 114, no 4, p. 2438-Article in journal (Refereed)
    Abstract [en]

    Modal analyses of violins show several strong modes in the low frequency range. Holographic interferograms suggest that four strong modes can be interpreted as doublets having two and three nodal planes that intersect a cylinder with a roughly elliptical cross section at the bridge [A. Runnemalm, N.-E. Molin, and E. Jansson, J. Acoust. Soc. Am. 107, 3452-3459 (2000); M. Roberts and T. D. Rossing, Catgut Acoust. Soc. J. 3, 9-15 (1998)]. This is especially clear when the instrument is viewed simultaneously from three sides using mirrors, and the holographic system is made sensitive to in-plane motion as well. These doublets are not unlike those observed in cylindrical vibrators such as bells, and they remind us that a violin is a 3-dimensional object

  • 57.
    Runnemalm, Anna
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Air cavity modes in sound boxes recorded by TV holography1999In: Joint meeting, 137th regular meeting of the Acoustical Society of America, 2nd convention of the European Acoustics Association: Forum Acusticum 99, integrating the 25th German Acoustics DAGA Conference : Technical University of Berlin, Berlin, Germany, 15 - 19 March 1999 ; [program with abstracts], Woodbury, NY: Acoustical Society of America (ASA), 1999Conference paper (Refereed)
  • 58.
    Runnemalm, Anna
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Operating deflection shapes of the plates and standing aerial waves in a violin and a guitar model2000In: Acustica, ISSN 0001-7884, Vol. 86, no 5, p. 883-890Article in journal (Refereed)
    Abstract [en]

    Phase modulated TV holography is used to measure sound pressure variations of standing waves of the air inside cavities of transparent models of a violin and a guitar. The accompanying motions, the Operating Deflection Shapes (ODSs) of the now white painted walls of the enclosures are measured using TV holography. Experimental measurements of the ODSs are compared to finite element calculations of the coupled air cavity and plate motion

  • 59.
    Runnemalm, Anna
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jansson, Erik
    Kungliga tekniska högskolan, KTH.
    On operating deflection shapes of the violin body including in-plane motions2000In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 107, no 6, p. 3452-3459Article in journal (Refereed)
    Abstract [en]

    Earlier investigations have assumed only "out-of-plane" vibrations of the plates of the violin. The violin body can, however, be described as a thin-walled, double-arched shell structure and as such it may very well elongate in one direction as it contracts in another. Therefore, at least two orthogonal vibration components have to be included to describe the vibrations. The operating deflection shapes (ODSs) of a good, professionally made and carefully selected violin were therefore measured in several directions by TV holography to determine both "in-plane" and out-of-plane vibration components of the ODSs. The observations were limited to the frequency range 400-600 Hz, as this interval includes two most-prominent resonance peaks of bridge mobility and sound radiation as well as a third poorly radiating resonance. These three peaks clearly showed orthogonal vibration components in the ODSs. The vibration behavior of the violin body, sectioned in the bridge plane, was interpreted as the vibrations of an "elliptical tube" with nodal diameters. The number of nodal diameters increases from two to three in the selected frequency range. The TV holography measurements were supported by electrodynamical point measurements of bridge mobility, of air volume resonances, and by reciprocity, of radiation properties. Furthermore, a fourth mode, the air mode, A1, is involved indirectly in the sound radiation via influence on the body vibrations.

  • 60.
    Runnemalm, Anna
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jansson, E.V.
    Kungliga tekniska högskolan, KTH.
    Operating deflection shapes and the function of the violin1998In: Årsrapport: Årsrapport, Stockholm: Department of Speech, Music and Hearing, Royal Institute of Technology , 1998, p. 5-17Chapter in book (Other academic)
  • 61. Saldner, Henrik
    et al.
    Jansson, E.V.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Video demonstration of violin body vibrations1992In: Proceedings of the International symposium on musical acoustics: August 28- September 1, 1992, Shinjuku and Chofu, Tokyo, Japan., Tokyo: Musical Acoustics Research Group of Acoustical Society of Japan , 1992Conference paper (Refereed)
  • 62.
    Saldner, Henrik
    et al.
    Luleå tekniska universitet.
    Mohan, Nandigana K.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Comparative TV holography for vibration analysis1995In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 34, no 2, p. 486-492Article in journal (Refereed)
  • 63. Saldner, Henrik
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jansson, E.V.
    Measurements of the sound distribution from vibration modes of a violin using reciprocity and electronic holography1995In: Proceedings of the international symposium on musical acoustics, 1995Conference paper (Refereed)
  • 64. Saldner, Henrik
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mohan, K.N.
    Simultaneous measurements of out-of-plane displacement and slope by electronic holography1994In: Recent advances in experimental mechanics: proceedings of the 10th International Conference on Experimental Mechanics, Lisbon, Portugal, 18 - 22 July 1994 / [ed] J.F. Silva Gomes, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1994Conference paper (Refereed)
  • 65. Saldner, Henrik
    et al.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mohan, N.K.
    Desensitized TV holography applied to static and vibrating objects for large deformation measurements1996In: Laser Interferometry VIII: Techniques and Analysis, Bellingham, Wash,: SPIE - International Society for Optical Engineering, 1996, p. 342-349Conference paper (Refereed)
    Abstract [en]

    This paper illustrates a real time desensitized outof-p1ane displacement configuration for the measurement of large deformations of a diffusely reflecting object. The optical configuration is implemented to study the behavior of engineering structures subjected to large static as well as vibration deflections. Phase stepping is provided in the optical set-up to obtain the deformation maps from the interferograms. For vibration analysis, the possibility of incorporating both phase stepping and bias vibration on a single mirror is also demonstrated. Theoretical analysis along with experimental results are presented

  • 66.
    Saldner, Henrik O.
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Applications of reciprocity, electronic holography and shearography in statics1994In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 34, no 4, p. 334-339Article in journal (Refereed)
    Abstract [en]

    This paper illustrates the use of reciprocity in electronic-holography experiments to determine unknown forces or couples acting on a mechanical structure. Electronic holography and electronic shearography are simple, fast and contact-free methods for the measurement of deformation fields or gradients of deformation fields, both for static and sinusoidal loadings. From a first measurement, the deformation field of the structure for a known force is determined. In a second experiment, the deformation field for the unknown quantity is measured. Reciprocity is then used to determine the unknown quantity. These optical methods are useful tools for the understanding of reciprocity.

  • 67.
    Saldner, Henrik O.
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jansson, Erik V.
    Kungliga tekniska högskolan, KTH.
    Vibration modes of the violin forced via the bridge and action of the soundpost1996In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 100, no 2, p. 1168-1177Article in journal (Refereed)
    Abstract [en]

    The action of the soundpost in a violin is not well understood and fundamental knowledge is needed. Therefore low-frequency forced modes, operating deflection shapes, 250-600 Hz of a violin were investigated. Harmonic, sine wave, excitation was applied via the bridge (resembling playing) or via the sound from a loudspeaker. The latter excitation gives a reciprocal measure of radiativity. The modes were investigated with TV-holography and electro-acoustical admittance measurements. A carefully selected violin was investigated without soundpost, with soundpost, and with the soundpost position shifted toward the centerline, Answers were sought to three questions: Which are the violin modes forced via the bridge? To what extent do they radiate sound? What is the action of the soundpost? The observed modes were mostly not pure normal modes but mode combinations. Generally there is a nodal line close to the soundpost position of the plates. Schelleng has hypothesized that the main action of the soundpost is to make the violin nonsymmetric. The first top plate mode with soundpost can be looked upon as a combination of the first symmetric top plate mode and the first asymmetric mode without soundpost, The first mode is an effcient radiator and the second mode transfers the string vibrations via the bridge to the top plate efficiently. The asymmetric first mode with the soundpost is thus both excited and radiates sound. Our experimental results make the hypothesis plausible, but show that body (global) modes play an important role too. In the range 500 to 600 Hz, a body mode, C3, constitutes a major part. The C3 mode has a nodal line close to the normal soundpost position and is especially interesting as it seems to form a quality mark of a good violin

  • 68.
    Saldner, Henrik O.
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jansson, E.V.
    Kungliga tekniska högskolan, KTH.
    Sound Distribution from Forced Vibration Modes of a Violin Measured by Reciprocity and TV Holography1997In: C A S Journal, ISSN 1053-7694, Vol. 3, no 4, p. 10-16Article in journal (Refereed)
  • 69.
    Saldner, Henrik O.
    et al.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Stetson, Karl A.
    Fourier-transform evaluation of phase data in spatially phase-biased TV holograms1996In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 35, no 2, p. 332-336Article in journal (Refereed)
    Abstract [en]

    TV holograms for spatial phase stepping are formed with a small angular offset between the object and the reference beams to give a spatial frequency bias to the pattern recorded by the TV camera. It is common to set the bias so that there is a 90° or 120° phase shift between adjacent pixels and to use the irradiance of three or more adjacent pixels to evaluate the phase of the interference. We report the Fourier-transform evaluation of such recordings to obtain their phase data. We also demonstrate the direct calculation of the phase difference between successive recordings without intermediate calculation of the random phase of each hologram. This technique is proposed as an approach to pulsed TV holography

  • 70.
    Sjödahl, Mikael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Benckert, Lars
    Molin, Nils-Erik
    Marklund, O.
    Optical metrology at Luleå University of Technology, LTU, Sweden1999In: Recent research developments in optical engineering, Trivandrum: Research Signpost, 1999, p. 279-293Chapter in book (Other academic)
  • 71.
    Wåhlin, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Fällström, Karl-Evert
    Gustavsson, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Molin, Nils-Erik
    Wave propagation in plates studied by pulsed hologram interferometry1989In: The Sixth Meeting in Israel on Optical Engineering: proceedings : 19-21 December 1988, Tel Aviv, Israel / [ed] Rami Finkler; Joseph Shamir, Bellingham, Wash: SPIE - International Society for Optical Engineering, 1989, p. 146-53Conference paper (Refereed)
    Abstract [en]

    Isotropic and non-isotropic plates are impacted by a ballistic pendulum. The bending waves that are generated are studied with holographic interferometry using a double pulsed ruby laser as light source. The pulse shape changes with time because of the dispersivity of the waves. Initially the fringe pattern in the isotropic case is cylindrically symmetric and determined from an initial value problem. Later, when the waves have reached the plate rim, in- and outgoing waves gradually develop fringe patterns which in the end will be a combination of eigenmodes of the plate. A solution to the corresponding Kirchhoff plate equation is presented, which in the special case when the impact is modelled as a Dirac-pulse in space and time, is shown to depend only of the distance to the impact point divided by the square root of the time after impact and a parameter containing plate parameters. From the slope of the central deflection material parameters can be determined. Another solution, assuming a finite impact time, is shown to agree better with experiments. Results from investigations of non-isotropic materials are also presented.

  • 72.
    Wåhlin, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Molin, Nils-Erik
    On structure-borne sound: experiments showing the initial transient acoustic wave field generated by an impacted plate1994In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 96, no 5, p. 2791-2797Article in journal (Refereed)
    Abstract [en]

    The initial propagating transient acoustic field in air generated by an impacted plate is visualized. The transient traveling flexural waves in the plate created by the impact are shown, simultaneously. The experiments are performed using double pulsed holographic interferometry. It is shown that flexural waves in a plate act as a series of traveling acoustic sources. Since the flexural waves in the plate are dispersive the trace matched acoustical waves further away from the impact source propagate at a smaller angle relative to the plate than those closer to the impact. An observer situated close to the plate and away from the impact point will first receive high-frequency components of the sound. A quantitative evaluation of the acoustic field also shows that if there is a transient increase in pressure on one side of the plate there will be a similar decrease on the other side.

  • 73.
    Zipser, L.
    et al.
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Franke, H.
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Olsson, Erik
    Molin, Nils-Erik
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ultrasound object fields in air reconstructed using digital phase conjugation2002In: Proceedings: 2002 IEEE Ultrasonics Symposium : October 8 - 11, 2002, Forum Hotel, Munich, Germany / [ed] Donald E. Yuhas, Piscataway, NJ: IEEE Communications Society, 2002, p. 765-768Conference paper (Refereed)
    Abstract [en]

    A scanning laser Doppler vibrometer is used to record 2D ultrasound fields in air. The laser light of the vibrometer traverses the sound field to and from a rigid reflector and determines the velocity field, a quantity proportional to the sound pressure rate, in each scanned point relative to the sound source. The object sound is the scattered field from objects outside the recording area. Digital reconstruction using phase conjugation (time reversal) of the object sound field is then performed and the original object field intensity and phase is reconstructed.

  • 74.
    Zipser, Lothar
    et al.
    Hochschule für Technik/Wirtschaft, University of Applied Sciences, Friedrich-List-Platz.
    Franke, Heinz
    Hochschule für Technik/Wirtschaft, University of Applied Sciences, Friedrich-List-Platz.
    Olsson, Erik
    Molin, Nils-Erik
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Reconstructing two-dimensional acoustic object fields by use of digital phase conjugation of scanning laser vibrometry recordings2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 29, p. 5831-5838Article in journal (Refereed)
    Abstract [en]

    scanning laser Doppler vibrometer is used to record two-dimensional ultrasound fields in air. The laser light of the vibrometer traverses the sound field to and from a rigid reflector and determines the velocity field, a quantity proportional to the sound pressure rate, in each scanned point relative to the sound source. The object sound is the scattered field from objects outside the recording area. Digital reconstruction by use of phase conjugation (time reversal) of the object sound field is then performed, and the original object field intensity and phase is reconstructed

12 51 - 74 of 74
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf