Air leakage under membrane
When a slight leakage of air is heard during voicing, and the seal of the adhesive is intact, the origin of the air leak should be checked. Mostly this can be found out easily by feeling with a finger. In some cases the origin might be detected at the edge of the membrane. When the membrane is slightly tilted, air can leak sideways. The main cause for the membrane being tilted is that it is pushed too far down into the valve housing, when inserting it. When changing a membrane this should be carried out effortless and the membrane should not be pushed too far in.