Methods and apparatus to enforce a power off state of an audience measurement device during shipping

1. An audience measurement device, comprising:

a housing;

a media detector in the housing to collect media exposure data;

a packaging sensor to receive an audio signal;

a packaging detector to generate a frequency spectrum of the detected audio signal, to determine an energy of a first frequency associated with the generated frequency spectrum, to determine an energy of a second frequency higher than the first frequency and associated with the generated frequency spectrum, to compare a difference between the energy associated with the first frequency and the energy associated with the second frequency to a first threshold to determine whether the device is located within a package, wherein the packaging detector is to control a power mode based on the comparison between the difference and the threshold.

2. A device as defined in claim 1 , wherein the packaging detector compares the energy associated with the first frequency to a second threshold to determine whether there is enough data in the audio signal.

3. A device as defined in claim 2 , wherein the packaging detector comprises a first comparator to compare the difference between the energy associated with the first frequency and the second frequency to the first threshold to determine whether the device is located within the package, and a second comparator to compare the energy associated with the first frequency to a second threshold different from the first threshold to determine whether there is enough data in the audio signal.

4. A device as defined in claim 1 , wherein the packaging detector compares the difference between the energy associated with the first frequency and the energy associated with the second frequency to a second threshold different from the first threshold to determine whether there is enough data in the second frequency.

5. A device as defined in claim 4 , wherein the packaging detector comprises a first comparator to compare the difference between the energy associated with the first frequency and the energy associated with the second frequency to the first threshold to determine whether the device is located within the package, and a second comparator to compare the difference between the energy associated with the first frequency and the energy associated with the second frequency to the second threshold to determine whether there is enough data in the second frequency.

6. A device as defined in claim 1 , wherein the packaging detector is to cause the device to at least partially power down when the packaging detector determines that the device is located within the package.

7. A device as defined in claim 1 , further comprising a memory to store the collected media exposure data, wherein the packaging detector is to maintain a supply of power to a clock when the packaging detector determines that the device is located within the package.

8. A device as defined in claim 1 , wherein the package is a mailer.

9. A device as defined in claim 1 , wherein the media exposure data comprises at least one of a signature or an identification code to which the device is exposed.

10. A device as defined in claim 1 , further comprising a real-time clock.

11. A device as defined in claim 10 , further comprising a user interface to communicate information to a user, and wherein the user interface is to display a message to the user based upon the real-time clock.

12. A device as defined in claim 1 , wherein the packaging detector is to generate the frequency spectrum by performing a Fast Fourier Transform on the audio signal.

13. A device as defined in claim 1 , wherein the first frequency is approximately 600 Hz and wherein the second frequency is approximately 2400 Hz.

14. A device as defined in claim 1 , wherein the packaging sensor is to receive an audio signal for a period of time.

15. A method of enforcing a reduced power state in an audience measurement device during shipping of the device, comprising:

receiving an audio signal from a sensor indicative of a noise level outside the audience measurement device;

determining a frequency spectrum associated with the received audio signal;

determining an energy level in a first frequency band of the frequency spectrum;

determining an energy level in a second frequency band of the frequency spectrum, wherein the second frequency band is higher than the first frequency band;

calculating a difference between the energy of the first frequency band and the energy of the second frequency band;

comparing the difference between the energy of the first frequency band and the energy of the second frequency band to a muffling threshold; and

transitioning the audience measurement device to a reduced power state if the difference between the energy of the first frequency band and the energy of the second frequency band is greater than the muffling threshold.

16. A method as defined in claim 15 , further comprising comparing the energy of the first frequency band to a silent threshold to determine whether there is enough data in the first frequency band.

17. A method as defined in claim 15 , further comprising comparing the difference between the energy of the first frequency band and the energy of the second frequency band to an absent threshold to determine whether there is enough data in the second frequency band.

18. A method as defined in claim 15 , wherein the muffling threshold is selected based on audio characteristics of a package to receive the audience measurement device.

19. A method as defined in claim 15 , further comprising transitioning the audience measurement device to a normal power state if the difference between the energy of the first frequency band and the energy of the second frequency band is less than the muffling threshold.

20. A method as defined in claim 15 , further comprising collecting media exposure data with the audience measurement device.

21. A method as defined in claim 15 , wherein the first frequency is approximately 600 Hz and wherein the second frequency is approximately 2400 Hz.

22. A method as defined in claim 15 , wherein receiving the audio signal is performed periodically.

23. A method as defined in claim 15 , wherein receiving the audio signal is performed for a period of time.

24. A tangible machine readable medium having instructions stored thereon that, when executed by a processor, cause a machine to at least:

receive an audio signal from a sensor indicative of a noise level outside the audience measurement device;

determine a frequency spectrum associated with the received audio signal;

determine an energy level in a first frequency band of the frequency spectrum;

determine an energy level in a second frequency band of the frequency spectrum, wherein the second frequency band is higher than the first frequency band;

calculate a difference between the energy of the first frequency band and the energy of the second frequency band;

compare the difference between the energy of the first frequency band and the energy of the second frequency band to a muffling threshold; and

power off at least a portion of the audience measurement device if the difference between the energy of the first frequency band and the energy of the second frequency band is greater than the muffling threshold.

25. A machine readable medium as defined in claim 24 , further comprising instructions stored thereon that, when executed by a processor, cause the machine to compare the energy of the first frequency band to a second threshold to determine whether there is enough data in the first frequency band.

26. A machine readable medium as defined in claim 24 , further comprising instructions stored thereon that, when executed by a processor, cause the machine to compare the difference between the energy of the first frequency band and the energy of the second frequency band to a second threshold to determine whether there is enough data in the higher frequency band.