Abstract
This paper reports an efficient method for sound extraction from high-speed light spot videos reconstructed from the coded light spot images captured with a low-speed camera based on compressive sensing, but at the expense of consuming time. The proposed method first gets the high-speed video of the light spot that is illuminated on the vibrating target caused by sound. Then the centroid of the light spot is used to recover the sound. Simulations of the proposed method are carried out and experimental results are demonstrated. The results show that high-speed videos with a frame rate of 2000 Hz can be reconstructed with a low-speed (100 Hz) charge-coupled device (CCD) camera, which is randomly modulated by a digital micro-mirror device (DMD) 20 times during each exposure time. This means a speed improvement of 20 times is achieved. The effects of synchronization between CCD image recording and DMD modulation, the optimal sampling patterns of DMD, and sound vibration amplitudes on the performance of the proposed method are evaluated. Using this compressive camera, speech (counting from one to four in Chinese) was recovered well. This has been confirmed by directly listening to the recovered sound, and the intelligibility value (0–1) that evaluated the similarity between them was 0.8185. Although we use this compressive camera for sound detection, we expect it to be useful in applications related to vibration and motion.
Highlights
The principle for sound detection is simple: sound waves hit the objects in their traveling path causing the objects to vibrate, and sensors detect these vibrations, resulting in useful information that can be used for sound recovery
The recording speed sound recovered quality can be performed by the signal-to-noise ratio (SNR)
We developed a high-speed imaging system with a general low-speed charge-coupled device (CCD) camera based on compressive sensing for sound recovery
Summary
The principle for sound detection is simple: sound waves hit the objects in their traveling path causing the objects to vibrate, and sensors detect these vibrations, resulting in useful information that can be used for sound recovery. Sound detection by optical means has become increasingly attractive due to its simple optical setup, the fact that it is non-destructive, and it is widely varied and used in important applications. These applications include surveillance in hostile environments, intrusion detection, abnormal situation detection in public places, and search and rescue [1,2]. Non-contact optical devices such as Laser Doppler Vibrometers (LDVs) were used for sound recovery [3,4,5,6,7,8]. LDVs are based on the principle of laser interferometry, making. An emerging technology, Sensors 2018, 18, 1524; doi:10.3390/s18051524 www.mdpi.com/journal/sensors
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