Determining media device activation based on frequency response analysis

A method to monitor a media device with a meter, the method comprising:

• reusing first frequency values of audio sensed with a microphone to determine, by executing an instruction with a processor, a first frequency response of the sensed audio, the first frequency values having been determined to perform watermark detection during a first monitoring time interval;
• comparing, by executing an instruction with the processor, the first frequency response to a reference frequency response to determine whether the media device was active during the first monitoring time interval;
• controlling, by executing an instruction with the processor, operation of the meter based on the determination of whether the media device was active during the first monitoring time interval;
• and
• outputting, by executing an instruction with the processor, a device activity determination indicating whether the media device was active during the first monitoring time interval.

A non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor of a meter, cause the processor to at least:

• reuse first frequency values of audio sensed with a microphone to determine a first frequency response of the sensed audio, the first frequency values having been determined to perform watermark detection during a first monitoring time interval;
• compare the first frequency response to a reference frequency response to determine whether a media device was active during the first monitoring time interval;
• control operation of the meter based on the determination of whether the media device was active during the first monitoring time interval;
• and
• output a device activity determination indicating whether the media device was active during the first monitoring time interval.