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There’s a lot of similarity between the seismic imaging problem and ultrasound; the difference is for the most part a matter of scale. In some recent work, researchers brought exploration seismic imaging techniques to the medical ultrasound world with some success.

When one is working in a fluid like air or water, and mapping reflections from solid objects, some of the complexity is removed from the governing wave equation. The acoustic velocity in air is dependent on pressure, density and temperature, all of which vary relatively little in a small open-air volume. However, as I’m discovering, it is quite possible to run into non-linearities in the acoustic parameters near to a transducer.
As a seismologist interested in designing an in-air rangefinder array, I need to throw away some of the assumptions we typically would make in earth materials.

So, in no particular order, some issues to overcome:

• Finding a transducer that is small, cheap, somewhat omnidirectional, and can act as both a transmitter and a receiver.
• Finding the right balance between simplicity and performance in the analog front end.
• Designing with parts that do not require expensive assembly and are not themselves expensive.
• Buffering the data in the digital pipeline.
• Writing fixed point DSP implementations of the required filtering (e.g. Weiner deconvolution).

Ongoing discussion on the XCore forums