A filter support system for homogeneous wrinkle distribution on mouthpieces that shrink when cooled down during the production process

A mouthpiece for allowing the filters for protecting against contamination during passage of air flow by sensors in pulmonary function tests to homogeneously distribute wrinkles of mouthpieces during production, the mouthpiece comprising:

• a body formed from plastic raw material that is pressed in a female-male mold after it is brought to a melting temperature,
• two filters for allowing measurement of a speed of air passing through an airway in the mouthpiece based on a speed of sound waves moving in a space between the two filters,
• plural wrinkle regions formed on a surface of the two filters, wherein shrinkage of the two filters is different from shrinkage in the molded plastic raw material as a width (Xaperture) and a length (Yaperture) at a moment t1 reach new width (X′aperture) and new length (Y′aperture) values at a moment t2 after a cooling time of Δt;
• plural support lines that lower a mean of height values (h1, h2, h3, . . . hn) in the plural wrinkle regions to make wrinkles in each wrinkle regions predictable and reproducible, the support lines being produced from the plastic raw material used in the body, wherein the support lines are arranged to divide the two filters.