Many kinds of synthesized signals are used in our daily life, for example, warning signals for: vehicles moving in reverse, signaling the end of a washing machine cycle, electric pots boiling, and telephone bells. Sometimes these signals are quite similar and are mistaken for each other. The present investigation was designed to examine what kind of synthesized signals are appropriate for each purpose. The impressions of the timbre of the signals were judged using semantic differentials and identification of the signals was also examined. The results of these subjective evaluations were examined in relation to the physical properties of the signals. Since the impressions of sounds are sometimes different in different cultures, cross-cultural comparison was also made in order to find appropriate signals that can be used internationally.