Acoustic tomographic reconstruction of temperature and flow fields with focus on atmosphere and enclosed spaces: A review

Abstract

Acoustic travel-time TOMography (ATOM) technique is being widely used as a remote sensing method to determine the air temperature and air flow velocity distribution for both outdoor and most recently indoor applications. The first process of ATOM measuring system corresponds to compiling the travel-times of a sound signal between a set of loudspeakers (transmitters) and microphones (receivers) distributed over the tomographic area, whose positions are known. These measured travel-times would then be used as the input data for inverse algorithms to reconstruct the airflow velocity and air temperature fields. Accordingly, the accuracy of the measuring system depends heavily on both the accuracy of the estimated travel times and the tomographic algorithms. Recent investigations on arrays of acoustic tomography are pointed towards optimization and reliability purposes. Many experimental layouts have been identified that could allow reducing the number of transceivers while keeping the accuracy of measurements. This paper gives a detailed review and discussion of recent advances in ATOM development applied to outdoor and indoor applications covering 90 articles published since 1990. It discusses the relevant challenges, opportunities, pros, and cons of existing approaches in relation to both travel time estimations and reconstruction algorithms, providing strategies to improve the sector of acoustic tomography. Accordingly, a comparative study of various reconstruction techniques is performed based on its systematic errors and theoretical strategies. This review inspires more successful explorations to improve the estimation of the air temperature and the airflow velocity using the ATOM technique.