Abstract: A mechanical filter including at least two longitudinal mode vibrators, each of which is a piezoelectric ceramic member with constant modulus alloy members mounted separately on the top and bottom surfaces thereof. The two constant modulus alloy members have the same configuration, a frequency-temperature characteristic opposite to that of the piezoelectric ceramic member, and are aligned, at their individual centers, with the center of the piezoelectric ceramic member. The configurations of the two longitudinal mode vibrators can be predetermined to suppress higher order spurious vibration modes inside the mechanical filter itself.