Method and apparatus for pre-loading a piezoelectric transducer for downhole acoustic communication

A downhole acoustic transmitter for use in downhole communication, comprising:

• (a) an enclosure comprising a first end coupling, a second end coupling, a tubular outer housing having a first end coupled to the first end coupling and a second end coupled to the second end coupling, and an inner mandrel inside the outer housing and extending between the first and second end couplings such that an annular space is defined between the mandrel and the outer housing;
• (b) a piezoelectric transducer in the annular space, and having a first end contacting an inner face of the first end coupling in an axial direction;
• (c) a transducer preload means in the annular space and contacting the piezoelectric transducer such that a compressive preload force is applied to the piezoelectric transducer in the axial direction;
• and
• (d) an acoustic tuning element in the annular space and having a first end attached to the transducer preload means or to the piezoelectric transducer, and a second end that is axially spaced from the second end coupling such that an axial gap is defined there between, and such that an assembly comprising the piezoelectric transducer, transducer preload means and acoustic tuning element is attached to the enclosure only at the first end coupling.