Truncated aperture extrapolation for Fourier-based near-field acoustic holography by means of border-padding

• Although near-field acoustic holography (NAH) is recognized as a powerful and extremely fast acoustic imaging method based on the inverse solution of the wave-equation, its practical implementation has suffered from problems with the use of the discrete Fourier transformation (DFT) in combination with small aperture sizes and windowing. In this paper, a method is presented that extrapolates the finite spatial aperture before the DFT is applied, which is based on the impulse response information of the known aperture data. The developed method called linear predictive border-padding is an aperture extrapolation technique that greatly reduces leakage and spatial truncation errors in planar NAH (PNAH). Numerical simulations and actual measurements on a hard-disk drive and a cooling fan illustrate the low error, high speed, and utilization of border-padding. Border-padding is an aperture extrapolation technique that makes PNAH a practical and accurate inverse near-field acoustic imaging method.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

Keyword

Discrete fourier transformation

Extrapolation techniques

Fourier

Hard Disk Drive

Imaging method

Inverse solution

Near-field acoustics

Nearfield Acoustic Holography

Numerical simulation

Practical implementation

Small aperture

Truncation errors

Acoustic holography

Acoustics

Approximation theory

Discrete Fourier transforms

Extrapolation

Fourier analysis

Holographic interferometry

Imaging systems

Impulse response

Interferometry

Inverse problems

Probability density function

Acoustic imaging

accuracy

article

Fourier transformation

frequency modulation

holography

imaging

mathematical analysis

measurement

noise measurement

prediction

priority journal

quantum mechanics

simulation

sound detection

spectroscopy

waveform

Publication and Content Type

ref (subject category)

art (subject category)