Precise estimate of ranging signals’TOA（time of arrival）is a key for wireless sensor networks nodes’acoustic localization.Several acoustic signals’TOA estimate methods are compared and an estimate method based on the digital signal rectifying process is introduced.It includes the following steps:increase of signal noise ratio

remove of DC（direct current）value

fullwave rectifying process

low-pass filter process and TOA estimate.It is implemented with a dsPIC6014A microcontroller.Test results show that the time of computing is about 1.5s（10MHz clock）

sample length is 4 096（12bits of each sample data）.The estimate error of TOA is less than 3.5% with 30m distance.