In recent years, many kinds of sign sounds have come into use in our daily life. The purpose of sign sounds is to communicate a message. However the ease of message understanding and listening comfort have rarely been taken into consideration. Because people have different tastes and attach a different "image" to sign sounds according to their individual sensibility, it is important for each person to be able to make melodies freely and easily, and customize sign sounds. We propose a sign sounds design system using an Interactive Genetic Algorithm (IGA). The proposed system produces a melody of two bars based on this IGA. A melody is considered to be a sort of "organism," whose chromosome consists of genes indicating the length, pitch, and velocity of the notes of the melody. Experimental results showed that this system is effective for generating sign sounds. In creating auditory signals, it was found that the method of evolving part-by-part is better than the method of evolving the whole two bars.