Digital holographic sound field imaging beyond Nyquist frequency

This paper presents digital holographic sound field imaging method for sound fields containing frequencies above the Nyquist frequency. Digital holography is a non-invasive interference-based imaging technique that enables high-spatial-resolution visualization of sound fields using image sensors. However, according to Nyquist-Shannon sampling theorem, accurate frequency acquisition requires a frame rate at least twice the maximum frequency of the sound fields. This constraint limits the field of view due to readout bandwidth limitation of image sensors. To address this, we propose a technique that reconstructs high-frame-rate sound fields from lower-frame-rate recordings through computational reconstruction using the wavelength information of the sound-field images. Experimental results show that the proposed method achieves a twenty-fold improvement in temporal resolution and an eight-fold increase in the field of view compared to the conventional digital holographic method. This achieves sound field imaging even with low-frame-rate image sensors. • Digital holographic sound field imaging beyond the Nyquist limit is proposed. • Temporal resolution is improved twenty-fold by the proposed method. • Field of view is expanded eight-fold over the conventional digital holographic method. • The effectiveness of the proposed method was validated by a verification experiment.