A speech decoding method which generates an excitation signal and a synthesis filter from coded data and which obtains a speech signal based on the excitation signal and the synthesis filter. After preparation of a crown, the dentist presses the surface contour tool against the biting surface of the tooth to determine the depth settings for at least one burr in a surface tool that will remove the upper surface of the tooth and create a working surface for the material removal device. A bolt extends through bolt holes and draws the flanges against the spline to stretch the band around the pipes when the bolt is tightened against the force bars. In one embodiment, mini-lessons and follow-up activities are designed to be integrated into the learner’s daily experiences without requiring the learner to significantly deflect attention from his or her normal responsibilities or activities. The muffling structure further includes at least one muffling fiber body plugged in the receptacle.