A piezoelectric sounder (external drive type) is designed to produce sound at a stable sound pressure when it is driven at the frequency used to obtain the specified sound pressure, however it will also produce sound at other frequencies as well. Consequently, it can produce not only a single sound but also melodies and other complex sounds, enabling it to be used in such applications as operation confirmation sounds, alarms, melodies and pseudo sounds.
However, there are cases in which the sound pressure level becomes very small depending upon the drive frequency, although this will also depend upon the frequency characteristics of sound pressure level of each product, so check and evaluate the product before using it.