A method and apparatus for encoding a digital image is disclosed. It is determined if a detected object interaction with the touch screen is a valid input object interaction with the touch screen. 5% by weight, calculated as K2O and based on the mixed oxide powder, and\u2014the dispersion has a fraction of mixed oxide powder in the dispersion of 25% to 40% by weight, the sum of water and mixed oxide powder is at least 98% by weight and the pH is 9 to 11. When one user executes the dynamic document, the dynamic field takes on one value. The test panel has a sound guiding hole in the common part with the enclosed cavity for transmitting the sound of the noise source into the interior of the coupling cavity.