preferably help insure that no charge passes between the outside of the sensor 510 and the shielding layers 410 and 413 the layers 409 and 414 are preferably uniformly distributed having very few irregularities or discontinuities furthermore the layers 409 and 414 preferably adhere smoothly and evenly to the surfaces they contact in some embodiments a biocompatible adhesive 416 is used to improve the mechanical and acoustic connection between the compliant membrane 415 and skin the biocompatible adhesive 416 can be u201c hydrogel u201d as previously described which can be positioned at the skin sensor interface to improve sensitivity and acoustic mechanical coupling in some embodiments the biocompatible adhesive 416 is smeared onto the human skin surface where the sensor 510 will be placed and the sensor 510 is pressed onto the same area of the skin the adhesive 416 can also be placed on the sensor 510 before it is pressed into place in some embodiments the biocompatible adhesive 416 is located beneath a removable strip not shown on the sensor when the sensor 510 is packaged and the user can remove the strip to reveal the biocompatible adhesive 416 underneath immediately prior to using the sensor 510 as schematically illustrated in fig5 the layers described above can form a sensor 510 and leads.