Cox, Johnson, and Alexander (2012) report cochlear dead regions (DRs) occur when inner hair cells at a given frequency are lost or malfunctioning. Previous publications have suggested hearing-aid high-frequency gain should be attenuated in the presence of high frequency DRs.
Precondition for a VdS approval procedure, among others, is proof of a certified quality management system in accordance with DIN EN ISO 9001 for the manufacturing facility of the product.
Type approval. Type Approval or Certificate of Conformity is granted to a product that meets a minimum set of regulatory, technical and safety requirements. Generally, type approval is required before a product is allowed to be sold in a particular country, so the requirements for a given product will vary around the world.