My father-in-law used to tape family mealtime conversations. When played back, the background noise -like silverware hitting plates and doors closing - is surprisingly prominent. Why is it that we filter these sounds out as they happen, but seem unable to filter them out when we listen to the recording?rnMicrophones are wonderfully objective devices. They detect variations in absolute pressure orthe pressure gradient on a particular axis and faithfully transduce these into electrical signals. In contrast our ears have a brain attached, and between them they do a much more subjective job - interpreting our acoustic environment, not just recording it.
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