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Laut Patent hat Beyer einen Fable für Polyurethan:
https://patents.google.com/patent/DE102018126823A1
Beschreibung zum Nutzen:
Hier sieht man interessanterweise auch den frequenzabhängigen Dämpfungsfaktor:
https://patentimages.storage.googleapis.com/39/c8/18/a7c617287143d3/DE102018126823A1_0012.png
Die Scheiben dämpfen wohl alle > 6 kHz.
https://patents.google.com/patent/DE102018126823A1
Beschreibung zum Nutzen:
In the case of headphones, there are often unwanted reflections on the head of a user and inside the headphones or the receiver shell. These occur as soon as the wavelength of the emitted sound is in the order of the distance between the receiver shell and the head. Multiple reflections on the head and receiver shell lead to standing waves and consequently to unwanted highs in the tones in the high frequency range, i.e. at high frequencies. As a rule, headphones have only one loudspeaker in each receiver shell, which covers the entire listening area. For signals with a low frequency, the membrane of the loudspeaker vibrates in a piston-like manner and therefore in phase, as a result of which the sound is radiated from the membrane almost over its entire surface. At high frequencies (high frequencies), however, vibration patterns, so-called partial vibrations, form on the membrane. The loudspeaker becomes a bending wave converter. Parts of the membrane now vibrate with different phases. As a result, some of these vibrations cancel each other out in certain areas and ultimately only a sub-area of the membrane contributes to the actual sound radiation. Typically, the area of sound radiation relevant for the high frequencies lies in the center of the membrane. Nevertheless, the position and shape of the partial vibrations are strongly frequency-dependent, which means that the area on the membrane that is relevant for sound radiation can vary greatly with increasing frequency.
Hier sieht man interessanterweise auch den frequenzabhängigen Dämpfungsfaktor:
https://patentimages.storage.googleapis.com/39/c8/18/a7c617287143d3/DE102018126823A1_0012.png
Die Scheiben dämpfen wohl alle > 6 kHz.