A blind algorithm for reverberation-time estimation using subband decomposition of speech signals.

An algorithm for blind estimation of reverberation time (RT) in speech signals is proposed. Analysis is restricted to the free-decaying regions of the signal, where the reverberation effect dominates, yielding a more accurate RT estimate at a reduced computational cost. A spectral decomposition is performed on the reverberant signal and partial RT estimates are determined in all signal subbands, providing more data to the statistical-analysis stage of the algorithm, which yields the final RT estimate. Algorithm performance is assessed using two distinct speech databases, achieving 91% and 97% correlation with the RTs measured by a standard nonblind method, indicating that the proposed method blindly estimates the RT in a reliable and consistent manner.

Contrast echocardiography for pulmonary blood volume quantification.

Pulmonary blood volume quantification is important both for diagnosis and for monitoring of the circulatory system. It requires employment of transpulmonary indicator dilution techniques, which are very invasive due to the need for double catheterization. This paper presents a new minimally invasive technique for blood volume quantification. An ultrasound contrast agent bolus is injected peripherally and detected by an ultrasound transducer in the central circulation. Several echocardiographic views permit simultaneous detection of contrast in different cardiac cavities and central vessels, and acoustic backscatter measurements produce multiple indicator dilution curves (IDCs). Contrast mean-transit-time differences are derived from the IDC analysis and multiplied times cardiac output for the assessment of blood volumes between different detection sites. For pulmonary blood volume estimates, the right ventricle and the left atrium IDCs are measured. The mean transit time of the IDC is estimated by specific modelling. The Local Density Random Walk and the First Passage Time models were tested for IDC interpolation and interpretation. The system was validated in vitro for a wide range of flows. The results show very accurate volume measurements. The volume estimate determination coefficient is greater than 0.999 for both model fits. A preliminary study in patients shows promising results.