Methods, apparatus, and machine-readable storage media to monitor media presentations are disclosed. A disclosed example apparatus includes a locator to compare a location of a mobile device with a set of reference locations at which audio monitoring is to be performed. The disclosed example apparatus further includes an audio receiver to enable a microphone of the mobile device to collect audio for media monitoring when (1) the location of the mobile device corresponds to a first one of the reference locations and (2) a media presentation monitor at the first one of the reference locations indicates a likelihood of media being presented at the first location satisfies a threshold. In some disclosed examples, the audio receiver of the example apparatus is to disable the microphone from collecting audio for media monitoring when the location of the mobile device does not correspond to any of the reference locations.

Methods and apparatus to collect media identifying data are disclosed. An example system to monitor media includes a printed circuit board defining a sound hole, the sound hole including a cylindrical portion and a chamfered opening, the sound hole having an effective length-to-width ratio of about 1.25; a memory including machine readable instructions; and a processor to execute the instructions to process the audio data collected through the sound hole to obtain media identifying data.

Methods and apparatus to collect media identifying data are disclosed. An example system to monitor media includes a printed circuit board defining a sound hole, the sound hole including a cylindrical portion and a chamfered opening, the sound hole having an effective length-to-width ratio of about 1.25; a memory including machine readable instructions; and a processor to execute the instructions to process the audio data collected through the sound hole to obtain media identifying data.

An example apparatus to monitor media that is presented via a mobile device includes: an application monitor to determine when media presentation software is being executed by the mobile device; and a metering information collector to collect at least one of a signature or a code of the media presented by the media presentation software based on the media presentation software being executed by the mobile device.

An example apparatus to monitor media that is presented via a mobile device includes: an application monitor to determine when media presentation software is being executed by the mobile device; and a metering information collector to collect at least one of a signature or a code of the media presented by the media presentation software based on the media presentation software being executed by the mobile device.

Methods and apparatus to determine a state of a media presentation device are disclosed. Example disclosed methods include generating a first set of weighted coefficients based on first audio received by first and second microphones at a first time. Example disclosed methods include generating a second set of weighted coefficients based on second audio received by the first and second microphones at a second time after the first time. Example disclosed methods include comparing the first set of coefficients and the second set of coefficients to generate a similarity value. Example disclosed methods include, when the similarity value satisfies a threshold, determining that the media presentation device is in a first state. Example disclosed methods include, when the similarity value does not satisfy the threshold, determining that the media presentation device is in a second state.

Methods and apparatus to determine a state of a media presentation device are disclosed. Example disclosed methods include generating a first set of weighted coefficients based on first audio received by first and second microphones at a first time. Example disclosed methods include generating a second set of weighted coefficients based on second audio received by the first and second microphones at a second time after the first time. Example disclosed methods include comparing the first set of coefficients and the second set of coefficients to generate a similarity value. Example disclosed methods include, when the similarity value satisfies a threshold, determining that the media presentation device is in a first state. Example disclosed methods include, when the similarity value does not satisfy the threshold, determining that the media presentation device is in a second state.

A system for quantifying viewer engagement with a video playing on a display includes at least one camera to acquire image data of a viewing area in front of the display. A microphone acquires audio data emitted by a speaker coupled to the display. The system also includes a memory to store processor-executable instructions and a processor. Upon execution of the processor-executable instructions, the processor receives the image data and the audio data and determines an identity of the video displayed on the display based on the audio data. The processor also estimates a first number of people present in the viewing area and a second number of people engaged with the video. The processor further quantifies the viewer engagement of the video based on the first number of people and the second number of people.

Methods and apparatus for crediting a media presentation device are disclosed. An example method includes detecting whether encoded information is present in audio obtained from a media device during a time period. Determining an on/off state of the media device based on a gain level applied by an automatic gain controller during collection of the audio. Crediting the media device with presenting media during the time period when the encoded information is detected irrespective of the on/off state determined for the media device, and not crediting the media device with presenting the media during the time period when the encoded information is not detected and the on/off state determined for the media device is an off state.

Methods and apparatus for crediting a media presentation device are disclosed. An example method includes detecting whether encoded information is present in audio obtained from a media device during a time period. Determining an on/off state of the media device based on a gain level applied by an automatic gain controller during collection of the audio. Crediting the media device with presenting media during the time period when the encoded information is detected irrespective of the on/off state determined for the media device, and not crediting the media device with presenting the media during the time period when the encoded information is not detected and the on/off state determined for the media device is an off state.