Leistner, PhilipPhilipLeistner2022-03-082022-03-082013https://publica.fraunhofer.de/handle/publica/310028The sound absorber has an extension element (3) that is connected with a planar element (1) through a connector (2). The intermediate gaps (4) are provided between the extension element and the connector and between two adjacent extension elements so as to form micro-perforated plate arrangement with acoustic effect. An air space with acoustic effect of a spring is formed between the extension element and the planar element so that an incident sound wave excites the air mass in the intermediate gaps to vibrate such that attenuation of sound wave is performed.de690patent102011107484