Acoustic Tomography

One of the projects that I'm currently working on is a method of measuring temperature and velocity fields using sound, called acoustic tomography. This method relies on the two properties of sound: it's speed is temperature dependent, and the sonic speed is relative to the motion of the fluid (in our case, air). The principle is similar to that used for sonic anemometers, the time taken for a sound to cross a distance is measured in two directions and the mean wind speed and temperature can be determined. If we set up a large number of speakers and microphones around a measurement area, it is possible to reconstruct the temperature and/or velocity fields within the area. This can be used to generate an image or video of the temperature and wind distribution.

This has been done before, however we are looking at much smaller scales in order to measure the flow in street canyons.

For more information, see my paper at the New Zealand Acoustic Society conference. Example code is also available from my section of the Matlab File Exchange.

The image above shows the temperature (colours) and wind velocity (arrows) field for votex shedding behind a cylinder. The top image shows the simulated flow, and the bottom one shows the reconstruction. The video below shows multiple frames of similar data. Unfortunately the resolution is low, if you would like to see the full video, please contact me.

New Slide Background

In preparation for next week's presentation, I got Amy Templeman to design some new Powerpoint slide backgrounds. I really like them, so I thought I'd share. The top one is for Nutaksas; the other is for the University of Auckland.

Upcoming Conferences

Next week (Nov 24-28), Travis will be speaking at two conferences. He will be presenting some recent developments in acoustic tomography at ENZCON 2008, "New Zealand’s leading national conference in electronics", as well as the New Zealand Acoustic Society Conference 2008. Acoustic tomography is a non-invasive method of measuring temperature and flow fields by measuring the time taken for sound to cross an area or volume.

Colleagues from the University of Auckland will also be presenting at both conferences.

Watch this space for details.

PhD Thesis Available

My PhD Thesis, "Online Learning of a Neural Fuel Control System for Gaseous Fueled SI Engines," is now available at lulu.com. This is a beautifully bound 153-page hardcover version of the dissertation including all the papers and a listing of the computer code used. If the price is too expensive for you, please feel free to email me for a free electronic copy. I'm not posting direct links for the first couple years so I can get some feedback as to who is interested in the work.

The cover was designed by Amy Templeman.