This paper presents experimental evidence of a localized phase for fast (sound) waves in a soft elastic medium doped with resonant encapsulated microbubbles, spanning up to 246 kHz. The transition to this localized phase is marked by an anomalous decrease in the mean free path, following a power law with a critical exponent near unity. Within the localized phase, the mean free path is 0.4-1.0 times the wavelength, transmitted intensity is well-described by self-consistent localization theory, and localization length decreases with increasing microbubble volume fraction. This research lays the groundwork for broadband control of localization in soft matter and provides a comparison with theoretical predictions.

Bernard R. Matis, Steven W. Liskey, Nicholas T. Gangemi, Aaron D. Edmunds, William B. Wilson, Virginia D. Wheeler, Brian H. Houston, Jeffrey W. Baldwin, Douglas M. Photiadis