A piezoelectric actuator , comprising: a suspension plate , wherein the suspension plate is a square structure, a length of the suspension plate is in a range between 4mm and 8mm, and the suspension plate is permitted to undergo a curvy vibration from a middle portion to a periphery portion ; a piezoelectric ceramic plate , wherein the piezoelectric ceramic plate is a square structure, a length of the piezoelectric ceramic plate is not larger than a length of the suspension plate , and the piezoelectric ceramic plate is attached on a first surface of the suspension plate , wherein when a voltage is applied to the piezoelectric ceramic plate , the suspension plate is driven to undergo the curvy vibration; an outer frame arranged around the suspension plate ; and at least one bracket connected between the suspension plate and the outer frame for elastically supporting the suspension plate , wherein the bracket comprises: an intermediate part (p21) formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate ; a first connecting part (p20) arranged between the intermediate part (p21) and the suspension plate ; and a second connecting part (p22) arranged between the intermediate part (p21) and the outer frame , wherein the first connecting part (p20) and the second connecting part (p22) are opposed to each other and arranged along the same horizontal line. a suspension plate , wherein the suspension plate is a square structure, a length of the suspension plate is in a range between 4mm and 8mm, and the suspension plate is permitted to undergo a curvy vibration from a middle portion to a periphery portion ; a piezoelectric ceramic plate , wherein the piezoelectric ceramic plate is a square structure, a length of the piezoelectric ceramic plate is not larger than a length of the suspension plate , and the piezoelectric ceramic plate is attached on a first surface of the suspension plate , wherein when a voltage is applied to the piezoelectric ceramic plate , the suspension plate is driven to undergo the curvy vibration; an outer frame arranged around the suspension plate ; and at least one bracket connected between the suspension plate and the outer frame for elastically supporting the suspension plate , wherein the bracket comprises: an intermediate part (p21) formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate ; a first connecting part (p20) arranged between the intermediate part (p21) and the suspension plate ; and a second connecting part (p22) arranged between the intermediate part (p21) and the outer frame , wherein the first connecting part (p20) and the second connecting part (p22) are opposed to each other and arranged along the same horizontal line. an intermediate part (p21) formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate ; a first connecting part (p20) arranged between the intermediate part (p21) and the suspension plate ; and a second connecting part (p22) arranged between the intermediate part (p21) and the outer frame , wherein the first connecting part (p20) and the second connecting part (p22) are opposed to each other and arranged along the same horizontal line. <EOS>