Armin Raabe LIM Leipziger Institut für Meteorologie, Manuela Starke, TU Dresden

Acoustic travel time tomography to observe temperature and flow fields simultaneously

Acoustic travel-time tomography is a remote sensing technique that uses the dependence of sound speed in air on temperature and flow speed along the sound propagation path. A combined tomographic analysis of travel-time measurements of acoustic signals along different paths through a measuring area gives information on the spatial distribution of temperature and flow fields within this area.

The acoustic tomographic method was developed for meteorological observations and has also been tested within the Barrel of Ilmenau to demonstrate its capability to simultaneously detect flow and temperature fields in a closed convection chamber. In order to obtain travel-time information along different paths, several transmitter receiver pairs were placed around the area under investigation. To reduce the necessary number of such transmitter receiver pairs it is possible to analyse the room impulse response which contains information on reflections of a sound signal at the walls of the investigated volume, and thus, contains information on sound propagation along different paths. It is shown that a three-dimensional acoustic monitoring of the room temperature can be realized with only one sound source and one sound receiver. Such a reduction of measurement equipment is a requirement for practicable and flexible use in indoor applications.