| CPC F24F 13/24 (2013.01) [F24F 2013/242 (2013.01)] | 19 Claims |

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1. An improved furnace comprising:
a housing comprising a combustion air chamber, a heat exchanger chamber, and a circulation blower chamber, wherein the combustion air chamber comprises a burner assembly and a combustion air fan;
a sound attenuation layer comprising an acoustic metamaterial layer tuned to attenuate sound for a frequency band, wherein the frequency band includes a frequency of operation of at least one of the burner assembly and the combustion air fan, and wherein the sound attenuation layer is coupled to a portion of the combustion air chamber; and
one or more housing openings fluidly connecting the combustion air chamber to an environment outside the housing, wherein each of the one or more housing openings provides less attenuation of sound emanating from within the combustion air chamber than the housing,
wherein the sound attenuation layer includes a discontinuous section that aligns with one or more of the housing openings.
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