Methods and apparatus to verify presentation of media content

1. An apparatus for use with a set-top box (STB) and a media presentation device, comprising:

an audio input interface to receive a first audio signal associated with a program selected by a user via the STB;

a microphone to receive a free-field radiating second audio signal output by at least one of the media presentation device or an audio system associated with the media presentation device;

a finite impulse response filter having adaptive coefficients to delay and to attenuate the first audio signal to form an estimate of the second audio signal;

a comparator to compare the second audio signal to the estimate of the second audio signal to form an output;

a privacy protector to facilitate burst mode operation of the comparator by periodically disabling the microphone and the comparator; and

an output interface to provide a value indicative of whether the program selected by the user via the STB is presented at the media presentation device based on the output.

2. An apparatus as defined in claim 1 , further including:

a first externally-exposed connector to communicatively couple the first audio signal from the STB to the apparatus via a first cable;

a second externally-exposed connector to communicatively couple the first audio signal from the apparatus to the media presentation device via a second cable; and

a third externally-exposed connector to provide the value via a third cable.

3. An apparatus as defined in claim 1 , further including an audio output interface to provide the received first audio signal to the media presentation device.

4. An apparatus as defined in claim 1 , further including a first housing to contain the audio input interface, the microphone, the comparator and the output interface, wherein the first housing is distinct from a second housing to contain the STB and is also distinct from a third housing to contain the media presentation device.

5. An apparatus as defined in claim 1 , further including a first housing to contain the audio input interface, the microphone, the comparator, the output interface and the STB, and a second housing to contain the media presentation device.

6. An apparatus as defined in claim 1 , wherein the value indicates a first logic state when the program selected via the STB is output via the media presentation device and indicates a second logic state when the program selected via the STB is not output via the media presentation device.

7. An apparatus as defined in claim 1 , wherein the comparator includes an echo canceller, and wherein the output of the comparator represents a magnitude of a residual signal.

8. An apparatus as defined in claim 1 , wherein the comparator includes a subtractor to subtract the estimate of the second audio signal from the second audio signal to form a residual signal.

9. An apparatus as defined in claim 8 , wherein the comparator further includes an adapter to adjust at least one of the adaptive coefficients to reduce the magnitude of the residual signal.

10. An apparatus as defined in claim 8 , wherein the comparator further includes a thresholder to compare an absolute value of the residual signal to a threshold to form the output of the comparator.

11. An apparatus as defined in claim 1 , wherein the apparatus is to be installed in-line between an audio output jack of the STB and an audio input jack of the media presentation device.

12. An apparatus as defined in claim 1 , wherein the comparator selects the delay and attenuation based on a maximum coefficient magnitude of the adaptive coefficients.

13. An apparatus as defined in claim 1 , wherein the filter is to set the adaptive coefficients to zero when the microphone is enabled.

14. An apparatus for use with a set-top box (STB) and a media presentation device comprising:

an audio input interface to receive a first audio signal associated with a program selected by a user via the STB;

a microphone to receive a free-field radiating second audio signal output by at least one of the media presentation device or an audio system associated with the media presentation device;

a comparator to compare the second audio signal to the first audio signal to form an output;

an output interface to provide a value indicative of whether the program selected by the user via the STB is presented at the media presentation device based on the output; and

a privacy protector including a timer to facilitate burst mode operation of the comparator by periodically disabling the microphone and the comparator.

15. A method to verify presentation at a media presentation device of media selected at a tuning device, comprising:

enabling a microphone to obtain a free-field radiating first audio signal output by the media presentation device;

implementing a privacy protocol by facilitating burst mode operation of the microphone, the burst mode operation to periodically disable the obtaining of the first audio signal;

applying a filter to a second audio signal associated with the media received at the tuning device to form an estimate of the first audio signal by delaying and attenuating the second audio signal;

comparing the first audio signal to the estimate of the first audio signal to form an output representative of whether the estimate of the first audio signal is present in the first audio signal; and

providing a value indicative of whether the media received by the tuning device was presented at the media presentation device based on the output.

16. A method as defined in claim 15 , wherein comparing the first audio signal to the estimate of the first audio signal includes:

subtracting the estimate of the first audio signal from the first audio signal to form a residual signal; and

comparing the residual signal to a threshold.

17. A method as defined in claim 15 , wherein comparing the first audio signal to the estimate of the first audio signal includes:

subtracting the estimate of the first audio signal from the first audio signal to form a residual signal;

updating a coefficient of the filter based on the residual signal;

computing a difference between a first magnitude of a first of the coefficients to a second magnitude of a second of the coefficients; and

comparing the difference to a threshold.

18. A method as defined in claim 15 , further including disabling the receiving of the first audio signal after the filter has converged its filter coefficients.

19. A method to verify presentation at a media presentation device of media selected at a tuning device, the method comprising:

receiving a first audio signal associated with the media received at the tuning device;

receiving a free-field radiating second audio signal output by the media presentation device;

implementing a privacy protocol by:

discontinuing the receiving of the second audio signal;

initializing a timer; and

restarting the receiving of the second audio signal when the timer expires;

comparing the second audio signal to an estimate of the second audio signal to form an output representative of whether the estimate of the second audio signal is present in the second audio signal; and

providing a value indicative of whether the media received by the tuning device was presented at the media presentation device based on the output.

20. A method as defined in claim 19 , wherein applying the filter to the first audio signal to form the estimate of the second audio signal includes delaying and attenuating the first audio signal.

21. A tangible machine-readable storage device or storage disc comprising instructions which, when executed, cause a machine to at least:

obtain, via a transducer, free-field radiating first audio signals output by a media presentation device;

implement a privacy protocol by facilitating burst mode operation of the transducer, the burst mode operation to periodically disable the transducer from obtaining the first audio signals;

apply a filter to a second audio signal associated with media received at a tuning device to form an estimate of the first audio signal, the filter to delay and to attenuate the second audio signal;

compare the first audio signal to the estimate of the first audio signal to form an output representative of whether the estimate of the first audio signal is present in the second first audio signal; and

provide a value indicative of whether the media received by the tuning device was presented at the media presentation device based on the output.

22. A machine-readable storage device or storage disc as defined in claim 21 , wherein the machine-readable instructions, when executed, cause the machine to:

subtract the estimate of the first audio signal from the first audio signal to form a residual signal; and

compare the residual signal to a threshold.

23. A machine-readable storage device or storage disc as defined in claim 21 , wherein the machine-readable instructions, when executed, cause the machine to compare the first audio signal to the estimate of the first audio signal by:

subtracting the estimate of the first audio signal from the first audio signal to form a residual signal;

updating a coefficient of the filter based on the residual signal;

computing a difference between a first magnitude of a first of the coefficients to a second magnitude of a second of the coefficients; and

comparing the difference to a threshold.

24. A machine-readable storage device or storage disc as defined in claim 21 , wherein the machine-readable instructions, when executed, cause the machine to implement the privacy protocol by:

discontinuing the receiving of the first audio signal;

initializing a timer; and

restarting the receiving the first audio signal when the timer expires.

25. An apparatus for use with a set-top box and a media presentation device comprising:

a transducer to receive a free-field radiating first audio signal output by the media presentation device;

a filter having adaptive weights to receive a second audio signal associated with a program selected by a user from an audio output line of the set-top box, and to process the second audio signal to generate a delayed and attenuated third audio signal;

a difference detector to subtract the third audio signal from the first audio signal to form a residual signal;

a privacy protector including a timer to facilitate burst mode operation by periodically disabling the transducer from receiving the first audio signal; and

a comparator to form a value indicative of whether the program selected by the user via the set-top box is presented at the media presentation device based on the residual signal.