1. A method of detecting voice activity from an input signal having an initial silent period and a speech period, the method comprising: determining occurrence of the initial silent period; computing an autoregressive (AR) parameter from the initial silent period; storing a test statistic of the input signal calculated during both the initial silent and speech periods in a database, wherein the test statistic is calculated from a product of the AR parameter adjusted by an autocorrelation function with a transpose of the AR parameter adjusted by the autocorrelation function; computing a threshold from the database based on one or more values of the test statistic during the initial silent period and one or more values of the test statistic during the speech period; and outputting a decision value based on the AR parameter and the threshold.