Options
1988
Journal Article
Titel
Sound absorbers of a novel membrane construction
Abstract
Porous or fibrous materials are used in a great variety of applications to absorb acoustic energy at medium and high frequencies above approximately 200 Hz. There are, however, cases where their open and rough surface entails certain disadvantages with respect to hygiene and cleaning requirements. For medium and low frequencies, which would also require a relatively large absorber thickness and weight, there is a need for an alternative absorber, the acoustically active components of which are formed exclusively by, ideally, even and smooth membranes. The sound absorber presented herein is of the reactive or resonant type with several different modes of vibration excitable in a complex system of rather thin, though comparatively stiff metal or plastic membranes. The absorption of the vibrational energy as stimulated by the sound waves impinging on the new type of acoustic lining or splitters is brought about solely by frictional forces in bounded shear layers formed in between specially shaped membranes moving against each other and relative to the air volumes adjacent to and between them. When suitably adjusted to the particular noise spectrum, these combined vibrational and damping mechanisms enable the construction of a new generation of sound absorber which no longer requires additional porous material to be incorporated in order to make it effective in a broad band of medium and low frequencies. The honeycomb structure, which forms the solid frame for the acoustic absorber, also makes it a relatively light and stable construction element for both room acoustic and industrial applications, where contamination of the absorber by dust in the air or pollution of the environment by abrasive deposits from the damping material is to be avoided under all circumstances.
;
Es wird über die Entwicklung eines neuartigen Resonanzabsorbers berichtet. Die schwingfähigen Elemente des "Membran-Absorbers" sind die Lochmembran, der Luftpropfen im Bereich des Loches, die impermeable Deckmembran sowie die in der dahinter angeordneten Kammer eingeschlossene Luft als Feder. Dieser komplexe Resonator benötigt zur Erzielung einer breitbandigen Wirkung bei mittleren und tiefen Frequenzen keinerlei zusätzliches Absorptionsmaterial. Seine rundum hermetisch gegenüber der Umgebung abgeschlossene Bauweise mit völlig glatten äußeren Oberflächen machen den Membran-Absorber besonders in solchen Anwendungsgebieten geeignet, wo hohe Anforderungen hinsichtlich Hygiene und Brandschutz zu stellen sind und es auf niedrige Strömungsverluste sowie geringes Bauvolumen und Gewicht ankommt. Am Beispiel von Schalldämpfer-Kulissen, die ganz aus Edelstahl gefertigt wurden, wird der Einsatz des Membran-Absorbers unter den besonders harten Einsatzbedingungen in Kohlegruben und Rauchgas-Reinigungsanlagen angesprochen.