1. A method for determining whether alcohol is consumed by a person in a vehicle, the method comprising: converting a voice signal received from said person in the vehicle into a plurality of voice frames; extracting predetermined features from a voice frame among the plurality of voice frames; determining, based on the predetermined features, whether said voice frame is from a voiced sound, an unvoiced sound, or background noise; extracting a first average energy for each of the voice frames that is determined as the voiced sound, wherein the first average energy is calculated by summing squares of N samples from energy n-N+1 to energy n and dividing by N; dividing the plurality of voice frames that is determined as the voiced sound into sections with a predetermined length; calculating a second average energy of the first average energy in each of the sections; computing a difference of the second average energy between neighboring sections, wherein the neighboring sections does not overlap one another; determining that alcohol is consumed by said person when the difference is less than a predetermined threshold; and enabling or disabling the vehicle based on the determination.