About

Michael Krane is a Research Professor affiliated with the Applied Research Laboratory, Aerospace Engineering, Acoustics, Mechanical Engineering, and the Center for Acoustics and Vibration at Penn State University. His contact information includes the email mhk5@psu.edu and phone number 814-863-0021. He is part of Penn State's Graduate Program in Acoustics, which was founded in 1965 and is recognized as a leading resource for graduate education in acoustics in the United States. The program offers degrees including Master of Engineering in Acoustics, Master of Science in Acoustics, and Doctor of Philosophy in Acoustics. The interdisciplinary nature of the program emphasizes research and education in acoustics, contributing significantly to the field through its academic and research activities.

Research topics

• Mechanics
• Acoustics
• Physics
• Computer Science
• Mathematics
• Geometry
• Astronomy

Selected publications

• Principal aerodynamic mechanisms in phonatory flow

  Physics of Fluids · 2026-03-01

  articleSenior author

  This article presents high-fidelity simulations of fully coupled interaction between a slightly compressible fluid and the compliant vocal folds through which it flows. The focus here is identification of the dominant aerodynamic mechanisms in phonation. The modified Immersed Finite Element Method is used to compute self-sustained vibration of three-layer, viscoelastic model vocal folds with a skewed elliptical shape. Simulations, performed for Reh= 2350 and reduced frequency f*= 0.11, and driven by a lung pressure of 1 kPa, were used to estimate terms of the integral mass conservation, momentum, and mechanical energy equations, as well the Bernoulli equation. The vocal folds vibrated at 227 Hz, with subharmonic modulation. Analysis of the surface motion showed three modes that captured >99% of the energy. Analysis using the integral equations shows that the aerodynamics is essentially described by a balance between pressure drag on the vocal folds and the pressure force pushing fluid through the vocal folds. Furthermore, it was shown that fluid dynamic friction is always negligible compared to the pressure forces. Flow work comprised the energetic input, and the primary output was the work on the vocal folds (21% of input), with losses comprising 70% of input. Analysis of the Bernoulli equation shows that the flow is inherently unsteady at the beginning and end of a vibration cycle, when the vocal folds are nearly closed, and that, in the jet flow region, the unsteady and convective accelerations nearly offset one another. These results are consistent with those from driven wall experiments.

  PublisherDOI

• Phase-averaged analysis of jet dynamics in a scaled-up vocal fold model with asymmetric motions

  Physics of Fluids · 2025-09-01 · 1 citations

  article

  This study focuses on the effects of glottal jet dynamics on phonation when one of the vocal folds does not move as much as the other. This can be a pathological condition, such as vocal fold paresis, in which a vocal fold is completely or partially paralyzed. Experiments were conducted using a 10× scaled-up model in a free-surface water tunnel. Two-dimensional vocal fold models with semi-circular ends were computer-driven inside a square duct with constant opening and closing speeds. Four cases were studied in which one vocal fold moved 0%, 50%, 75%, and 100% of the other; the last case being, of course, the nominally “healthy,” symmetric case. Time-resolved Digital Particle Image Velocimetry and pressure measurements along the duct centerline were made at a Reynolds number of 7200 and reduced frequency of 0.0261, corresponding to an equivalent life frequency of 97.5 Hz. Phase-averaged analysis of key contributors to sound production was conducted using terms in the streamwise integral momentum equation. The ultimate goal is understanding how asymmetric gap opening affects the dynamics, specifically vocal fold drag, and therefore, sound production. Results of this experiment show that this nominally simple flow encompasses multiple effects due to varying maximum gap opening, asymmetry due to partial motion of one vocal fold, blockage by the wall boundary layers, and pseudo-frequency effects arising when the two vocal folds move at different speeds. There is indeed a dependence of vocal fold drag on gap opening.

  PublisherDOI

• Application of robust principal component analysis for time domain source separation

  The Journal of the Acoustical Society of America · 2025-10-01

  article

  Time domain source separation of microphone array signals with non-stationary, impulsive sources using robust principal component analysis (RPCA) is presented. Time domain source separation with RPCA is applied to microphone array signals observing the aeroacoustic emission of a vortex ring interacting with the edge of a semi-infinite half-plane (V/E interaction). An impulsive spherical pressure wave is produced as a by-product of the generation of vortex rings and is observed by all microphones. With non-stationary, impulsive signal features, frequency domain source separation techniques may not sufficiently separate the sources, requiring a time domain approach. Source separation is achieved with RPCA, enabling accurate estimation of V/E source parameters, with theoretical predictions in good agreement. RPCA, in this application, shows improved performance when compared to other time domain source separation methods involving principal component analysis (PCA). RPCA provides a data-driven approach for impulsive source separation, requiring less user intervention than PCA. Furthermore, RPCA source separation enables improved V/E source waveform time series when compared to prior efforts, which utilized signal windows that excluded the impulsive pressure wave signal feature.

  PublisherDOI

• Time domain characterization of nonstationary low-Mach number aeroacoustic sources using principal component analysis

  The Journal of the Acoustical Society of America · 2024-09-01 · 1 citations

  article

  This paper presents the use of principal component analysis (PCA) for time domain microphone array denoising to characterize an impulsive aeroacoustic source, which is illustrated with the aeroacoustic emission caused by a vortex ring/edge interaction. Prior studies have used signal processing approaches that required assumptions about the source directivity or user intervention at low signal-to-noise ratio (SNR) conditions. In this context, PCA, a matrix decomposition tool which identifies the most common features across an ensemble of observations, provides a data-driven (hands-off) approach to signal processing. For microphone array time series, particular attention is paid to the temporal alignment of the signals to facilitate PCA. A time domain approach is necessary when sources are impulsive and nonstationary. Two such signal arrangements are discussed in this work. Results from this method are in good agreement with theory, validated by prior results using an ensemble averaging approach requiring user support. Furthermore, the results of this method are improved when compared to the ensemble averaging approach without user intervention. A SNR limit is identified where PCA becomes less effective for the vortex/edge interaction problem. This SNR limit is intended to aid in the design of similar future experiments.

  PublisherDOI

• Investigation of Flow-Induced Forces on Isolated Wall-Mounted Bluff Bodies

  2024-05-30

  article

  In this study, we explore how variations in the geometry of isolated wall-mounted bodies alter flow-induced forces, which are the primary source of rough wall boundary layer noise. Force is measured on various shapes: pyramids, cubes, cylinders, and hemispheres with a range of Reynolds numbers based from approximately 77,000 to 31,000 . Although each body shape is unique, there exists common flow features. Spectral characteristics of force are examined, noting key differences and commonalities across the range of shapes.

  PublisherDOI

• Aeroacoustic Source Separation of Non-Stationary Signals in Time Domain With RPCA

  2024-05-30 · 3 citations

  article

  An approach using Robust Principal Component Analysis (RPCA) for time domain acoustic source separation of microphone array signals is presented. Representation of non-stationary, potentially impulsive signals in frequency domain can often be ineffective, necessitating a time domain approach. One such application is the aeroacoustic emission of an individual vortex ring interacting with the edge of a semi-infinite half-plane, where microphone signals are polluted by the presence of a shock wave intrinsic to vortex generation. Both of these sources are impulsive and non-stationary. RPCA successfully performs the desired source separation, enabling characterization of the vortex/edge source. In the present application, RPCA shows improved performance relative to other time domain source separation techniques.

  PublisherDOI

• Acoustic cavitation detection in biomedical and underwater systems

  The Journal of the Acoustical Society of America · 2023-10-01

  article

  In the past decade, significant progress has been made in detecting and localizing cavitation for treatment monitoring in biomedical acoustics. Here, we compare passive cavitation imaging (PCI) and passive cavitation detection (PCD) during histotripsy in tissue-mimicking polyacrylamide (PA) hydrogels; PCI and bubble Doppler ultrasound are also used to evaluate flow-induced cavitation in a water tunnel. A Philips/ATL L7-4 transducer driven with a research ultrasound system was used for both PCI and Doppler imaging; a Sonic Concepts Y-107 transducer was used for PCD. PA hydrogels were treated with 1.5 MHz focused ultrasound (10-ms pulses with p + = 127 MPa/p− = 35 MPa repeated at 1-Hz for 60 s). In the 12-in. water tunnel, cavitation on a 1-in. diameter steel cylinder was imaged through a 0.5-inch-thick acrylic window while flow increased from 30–35 ft/s. High-speed cameras were also used in both experiments. In PA hydrogels, cavitation was observed with both PCI and PCD, although signal trends differed over the treatment. In the water tunnel, both PCI and Doppler ultrasound detected and localized cavitation events such as the horseshoe vortex, with measured amplitudes increasing with flow speed. These results show that cavitation imaging can be applied to multiple areas of acoustics. [Tissue work supported by NIHR01EB032860].

  PublisherDOI

• Aeroacoustic source prediction using material surfaces bounding the flow

  Fluid Dynamics Research · 2022-05-09

  articleOpen accessSenior author

  This article presents an extension of Liepmann's characterization of an aeroacoustic source in terms of the motion of a bounding surface containing the source region. Rather than using an arbitrary surface, we express the problem in terms of bounding material surfaces, identified by Lagrangian Coherent Structures (LCS), which demarcate flow into regions with distinct dynamics. The sound generation of the flow is written in terms of the motion of these material surfaces using the Kirchhoff integral equation, so that the flow noise problem now appears like that of a deforming body. This approach provides a natural connection between the flow topology, as revealed through LCS analysis, and sound generation mechanisms. As examples, we examine two-dimensional cases of co-rotating vortices and leap-frogging vortex pairs and compare estimated sound sources to vortex sound theory.

  PublisherOA PDFDOI

• Acoustic emission of a vortex ring near a porous edge. Part 1: theory

  Journal of Fluid Mechanics · 2022 · 11 citations

  Senior authorCorresponding
  • Physics
  • Mechanics
  • Acoustics

  The sound of a vortex ring passing near a semi-infinite porous edge is investigated analytically. A Green's function approach solves the associated vortex sound problem and determines the time-dependent pressure signal and its directivity in the acoustic far field as a function of a single dimensionless porosity parameter. At large values of this parameter, the radiated acoustic power scales on the vortex ring speed $U$ and the nearest distance between the edge and the vortex ring $L$ as $U^6 L^{-5}$ , in contrast to the $U^5 L^{-4}$ scaling recovered in the impermeable edge limit. Results for the vortex ring configuration in a quiescent fluid furnish an analogue to scaling results from standard turbulence noise generation analyses, and permit a direct comparison to experiments described in Part 2 that circumvent contamination of the weak sound from porous edges by background noise sources that exist as a result of a mean flow.

  PublisherDOI

• Phase-averaged, frequency dependence of jet dynamics in a scaled up vocal fold model with full and incomplete closure

  Physical Review Fluids · 2022-12-20 · 3 citations

  article

  This article explores the fluid dynamics underlying voice production. The key parameters explored in this paper are frequency (from adult male to children and adult females) and the degree of closure of the vocal folds during phonation. The latter can be a pathological condition, but is common in children and females without being problematic. The findings of this study indicate that changes in jet dynamics across the human frequency range may explain the fundamental differences between male and female voices.

  PublisherDOI

Recent grants

• Glottal Jet Aerodynamics

  NIH · $323k · 2002–2020

• Collaborative Research: Aerodynamic-aeroacoustic performance of poroelastic wings inspired by the silent plumage of owls

  NSF · $301k · 2018–2022

• Glottal Jet Aerodynamics

  NIH · $3.1M · 2002–2020

• Glottal Jet Aerodynamics

  NIH · $294k · 2002–2022

Frequent coauthors

• Timothy Wei

  Saratoga Hospital

  37 shared

• Lucy Zhang

  University Health Network

  20 shared

• Michael McPhail

  Pennsylvania State University

  19 shared

• M. L. Beninati

  17 shared

• Arnold A. Fontaine

  Pennsylvania State University

  15 shared

• Jeff Harris

  10 shared

• Feimi Yu

  10 shared

• Nathaniel J. Wei

  9 shared