Copper sulfide, CuS, was synthesized by an aqueous sonochemical method and it was investigated the effect of pH on crystal characteristics of CuS and IR absorbance. The formed CuS has main peaks as 27.68 degrees, 29.28 degrees, 31.79 degrees, 32.85 degrees, 47.94 degrees, 52.72 degrees and 59.3 degrees with the hexagonal structure. Average diameter of CuS was about 18 nm and molar ratio of Cu:S was as 1:1. The CuS prepared at pH 11 presents the highest visible light transmittance of 82.6% and that at pH 4 presents the highest IR rejected of 93.8%. The formation of CuS was affected by pH and led to new absorption band in the IR region. The CuS nanoparticles from this study could be used as thermal insulating materials for car- and house-window films with a high IR-cut.