This paper presents a new adaptation of a Gaussian echo model (GEM) to estimate the distances to multiple targets using acoustic signals. The proposed algorithm utilizes m-sequences and opens the door for applying other modulations and signal designs for acoustic estimation in a similar way. The proposed algorithm estimates the system impulse response and uses the GEM to limit the effect of noise before applying deconvolution to estimate the time of arrival (TOA) to multiple targets with high accuracy. The algorithm was experimentally evaluated for different scenarios with active (transmitters) and passive (reflectors) targets at proximity. In the case of closely spaced static passive targets, results show that 90% of the ranging errors are below 7 mm. When tracking two moving active targets approaching very close proximity, results show that 90% of the ranging errors are less than 10 mm.