| CPC G01N 29/4418 (2013.01) [G01N 29/04 (2013.01); G01N 29/4463 (2013.01)] | 14 Claims |

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1. An acoustic apparatus, comprising:
an enclosure having a body portion, an opening extending through the body portion, a ledge extending into the opening, a removable inserted disposed in the opening and resting on the ledge, one or more side walls extending from the body portion and an open side surrounded by the one more walls;
a microphone mounted in the body portion of the enclosure for receiving filtered sound waves from a portion of a floor when the floor on which the enclosure is placed is vibrated,
wherein each of the one or more side walls has a free end;
wherein together the free ends of the one or more side walls form a distal perimeter edge of the enclosure; and
wherein when the open side of the enclosure is placed on the portion of the floor, the body portion and one or more walls of the enclosure and the portion of the floor form a hollow enclosed region.
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