An apparatus and method for voice activity detection. A multiphase differential output rotating capacitive sampler achieves a frequency down conversion over as many specific frequency bands as are required for analysis. A chirp is created in the rotating sampler as the sum of arbitrary frequencies across the desired analysis band multiplied by a window function. The chirp is sampled at a rate of rotation synchronous with the last state of burst of the chirp, allowing a non-phase synchronous pattern in the coefficient values and allowing a high-Q and arbitrary decomposition of the signal. After the sample is taken, the next clock signal to the sampler is used to define the output voltage of the sampler by shorting the output, which is entirely capacitive, to ground. Processing occurs in the analog domain rather than digitally, avoiding the need for FFTs and allowing for greater speed and lower power consumption.