What is a holographic ultra-ear?
As unusual as it sounds, optical holography is a great way to “hear” sound in solid objects. While the use of lasers to detect surface vibrations is well-established, it has been virtually impossible to work with any target that was not mirror-like and stationary, because the returning laser signal is badly speckled and can be jittering. By using dynamic holography, these effects are removed: the speckle is compensated, and the jitter is adaptively compensated. There are two modes of the holographic ear. One detects Doppler shifts. The other detects surface vibrations. For an animation of the transient response of a photorefractive quantum well under the presence of a Doppler shifted beam look at Doppler Movie as a function of increasing Doppler frequency.
