Is an ICF home quieter than a stick framed home?

Absolutely. The exterior walls are two layers of continuous insulation, the density of solid concrete and a layer of ½" gypsum board on the inside all contribute to superior sound suppression of STC 50 for the whole building envelope. Note: A wood frame system of equivalent STC rating would be 2 x 4 studs spaced 16˝ o/c, with 3½˝ absorptive material, 1 layer of 5 /8˝ Type X gypsum board on resilient channels spaced 16˝ o/c, and 2 layers of 5 /8˝ Type X gypsum board on the other side. (Courtesy of 1995 NBCC Section A9.10.3.1 Wall #W5a)