Methods and apparatus to detect spillover in an audience monitoring system

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

• select first audio samples of a first audio signal received by a first microphone, the first audio signal associated with media;
• select first offset samples corresponding to a second audio signal received by a second microphone, the second audio signal associated with media, the first offset samples offset from the first audio samples by a first offset value;
• if a first count of occurrences of the first offset value satisfies a count threshold, accept the first offset value into a cluster;
• calculate a weighted average of a second offset value and the first offset value in the cluster;
• determine an origin direction of the media based on the weighted average;
• and
• when the origin direction is within a threshold angle, monitor audio codes embedded in the media.

An apparatus to distinguish local media from spillover media comprising:

• an audio sampler to sample a first audio signal from an audio source received by a first microphone and sample a second audio signal received by a second microphone from the audio source, the second microphone to be separated from the first microphone by a first distance;
• a direction detector to calculate an origin direction of the audio source based on a time difference between receipt of the first and second sampled audio signals, the first distance, and a speed of sound;
• and
• a code reader to, when the origin direction is within a threshold angle, detect an audio code embedded in at least one of the first sampled audio signal or the second sampled audio signal, the audio code to be representative of media corresponding to the first and second audio signals, the code reader to ignore the media when the origin direction exceeds the threshold angle.