The classical analysis of the effect of heat radiation assumes that the radiation is only slightly absorbed in the space of one acoustic wavelength; these results are sometimes then extrapolated to very low frequencies. This paper presents a re‐examination of the effect. Account is taken of the fact that a gas radiates energy of given electromagnetic wavelength in proportion to its corresponding coefficient of absorption. Since the peak absorption coefficient (nepers per meter) may be rather large in some gases, no restriction is placed upon the value of the absorption per acoustic wavelength. The result indicates that the increase of acoustic absorption per wavelength with decreasing frequency is markedly reduced when the maximum radiation absorption per wavelength approaches unity.

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