An audio receiver may include a mono/stereo detector that causes the audio receiver to output either a monophonic or a stereophonic signal based on a difference between a pilot energy signal and a filtered pilot energy signal. The audio receiver includes a filter that filters the pilot energy signal to generate a filtered pilot energy signal, wherein a variable leakage factor associated with the filter is used to minimize a noise level of the filtered pilot energy signal and to reduce a response time of the audio receiver.