Methods and apparatus for crediting a media presentation device

An apparatus, comprising:

• a code detector to detect encoded information present in ambient audio collected from a monitored location;
• an on/off detector to determine a first portion of a time period during which a media presentation device in the monitored location is in an on state and to determine a second portion of the time period during which the media presentation device is in an off state based on the ambient audio;
• and
• a location creditor to credit a third portion of the time period for the media presentation device to first media based on the encoded information and to credit a fourth portion of the time period different from the third portion based on the on state or the off state of the media presentation device during the fourth portion of the time period.

A computer readable storage medium comprising computer readable instructions which, when executed, cause a processor to at least:

• access ambient audio for a time period from a location including a media presentation device;
• detect encoded information present in the ambient audio;
• credit a first portion of the time period for the media presentation device to first media based on the encoded information;
• determine an on/off state of the media presentation device for a second portion of the time period different than the first portion based on the ambient audio;
• and
• credit the second portion of the time period based on the on/off state of the media presentation device.