Abstract
Sound-field imaging, the visualization of spatial and temporal distribution of acoustical properties such as sound pressure, is useful for understanding acoustical phenomena. This study investigated the use of parallel phase-shifting interferometry (PPSI) with a high-speed polarization camera for imaging a sound field, particularly high-speed imaging of propagating sound waves. The experimental results showed that the instantaneous sound field, which was generated by ultrasonic transducers driven by a pure tone of 40 kHz, was quantitatively imaged. Hence, PPSI can be used in acoustical applications requiring spatial information of sound pressure.
Highlights
Imaging of invisible physical phenomena by means of optical techniques aids the understanding of these phenomena
Sound pressure measurements using Laser Doppler vibrometry (LDV) were reported by Nakamura et al [1] and Harland et al [2, 3]
Three-dimensional sound field reconstruction based on tomography has been well-researched [11,12,13,14], and optical wave microphones [15, 16] and optical feedback interferometry [17] have been developed as scanning-based imaging methods
Summary
Imaging of invisible physical phenomena by means of optical techniques aids the understanding of these phenomena. Optical measurement of sound, which acquires acoustical quantities using optical methods, is of growing interest because of its contactless nature. Two-dimensional (2D) sound field imaging using scanning LDV was achieved [4,5,6,7,8,9,10]. Three-dimensional sound field reconstruction based on tomography has been well-researched [11,12,13,14], and optical wave microphones [15, 16] and optical feedback interferometry [17] have been developed as scanning-based imaging methods. The application of scanning-based imaging is limited to reproducible field such as sounds generated by a loudspeaker because the 2D acoustical quantities are acquired by a number of measurements
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