An aluminum extruded fin set includes a substrate and a plurality of dissipation fins mounted upright on it. There are gaps between heat dissipation fins. Each dissipation fin is divided into three child dissipation fins by two slanted cutouts. The child dissipation fin between two slanted cutouts is bent toward the gap between heat dissipation fins. When airflow passes by the gaps, the airflow velocity distribution is modified due to the bent child dissipation fins and the noise spectrum distribution is modified as well. Such a Hay-stack noise spectrum distribution is more comfortable for the listener than a conventional one.