An electrostatic pressure-gradient microphone capsule to be mounted essentially flush in or behind especially flat mounting surfaces includes a capsule housing with two sound inlet openings which may be divided, a diaphragm tightly mounted on a diaphragm ring, an electrode and possibly an acoustic friction. The formulations include a solubilizing agent, a reactive compound, a carbonate or bicarbonate salt, a water-soluble bleaching activator, a mold remediation enhancer containing Fe or Mn, and water. The device also has a connecting member or leash which extends between the backing and an anchor which is attached to bone or soft tissue. The structure will not only be more stable than before to prevent separation occurred by an external force, but also be waterproof equally.