Acoustic Bandwidth Compression (ABC)

We developed a real-time acoustic bandwidth compression algorithm that enables acoustic signals with large bandwidth to be compressed into a band that we can hear. The application of this algorithm is to enhance the diver experience, by enabling him or her to appreciate the rich soundscape the underwater world has to offer. A stereo implementation of the algorithm enables the diver to also localize the sound source. This further enhances the experience and may potentially improve dive safety.

Many animals and systems radiate ultrasound that contains valuable information, from bats to high-voltage power lines on land, and marine animals underwater. Initially motivated by an interest in listening to high-frequency dolphin vocalization, we developed a real-time bandwidth compressor that can translate the prominent features of ultrasound into the human hearing band. The algorithm requires no assumption on the frequency content of the signal of interest (except the maximum frequency).

We can tell the direction from which a sound originates to an amazing accuracy in air. However, our sound localization ability is ineffective underwater. By combining the ABC algorithm with a pair of directional receivers, we can provide appropriate Inter-aural Temporal Difference (ITD) and Inter-aural Intensity Difference (IID) cues to divers. We are thus able to introduce a sense of direction into their hearing in water.

Relevant Publications

[1] T. B. Koay, J. Tan, S. P. Tan, S. K. Yeo, H. Tay, M. Chitre, and J. Potter, “Enabling humans to hear the direction of sounds underwater - Experiments and preliminary results,” in OCEANS 2008 MTS/IEEE, (Quebec City, Canada), September 2008. [ DOI | .pdf ]
[2] T. B. Koay, J. Potter, M. Chitre, S. Ruiz, and E. Delory, “A compact real-time acoustic bandwidth compression system for real-time monitoring of ultrasound,” in OCEANS 2004 MTS/IEEE TECHNO-OCEAN '04, vol. 4, (Kobe, Japan), pp. 2323--2329, November 2004. [ DOI | .pdf ]