Abstract: An electret loudspeaker device including a diaphragm, a first perforated electrode and a first spacer is provided. The diaphragm includes a first electret, a second electret, a polymer layer and an electrode layer. At least one layer of the first electret or the second electret is formed by expanded polytetrafluoroethylene. The second electret is stacked on one side of the first electret, while the electrode layer is stacked on the opposite side of the first electret. The polymer layer is made of a hydrophobic material and is disposed on the second electret. The first perforated electrode is stacked on a first spacer and close to the polymer layer. The first spacer disposed between the diaphragm and the first perforated electrode supports the first perforated electrode over the diaphragm and defines a first chamber. A fabrication method of the electret loudspeaker device is also provided.

Abstract: A piezoelectric membrane and a forming method thereof are provided, wherein the method of forming the piezoelectric membrane includes providing a porous substrate film, which is a membrane structure formed by a plurality of fibers and has two main surfaces. Then, piezoelectric material solution is permeated into the porous substrate film and then hardened, such that the fibers are partially covered with the piezoelectric material.

Abstract: An electret loudspeaker device including a diaphragm, a first perforated electrode and a first spacer is provided. The diaphragm has an electret layer and an electrode layer. The first perforated electrode is stacked on a side of the diaphragm near the electret layer, and has multiple holes. The first spacer is stacked between the diaphragm and the first perforated electrode, and includes a first distribution area and plural second distribution areas. The first distribution area has first openings penetrating through the first spacer, and each first opening has a first opening space volume between the diaphragm and the first perforated electrode. Each second distribution area has second openings penetrating through the first spacer, and each second opening has a second opening space volume between the diaphragm and the first perforated electrode. A difference between the first and the second opening space volumes is greater than 10%.

Abstract: An electret loudspeaker device including a diaphragm, a first perforated electrode and a first spacer is provided. The diaphragm has an electret layer and an electrode layer. The first perforated electrode is stacked on a side of the diaphragm near the electret layer, and has multiple holes. The first spacer is stacked between the diaphragm and the first perforated electrode, and includes a first distribution area and plural second distribution areas. The first distribution area has first openings penetrating through the first spacer, and each first opening has a first opening space volume between the diaphragm and the first perforated electrode. Each second distribution area has second openings penetrating through the first spacer, and each second opening has a second opening space volume between the diaphragm and the first perforated electrode. A difference between the first and the second opening space volumes is greater than 10%.

Abstract: An electret loudspeaker device including a diaphragm, a first perforated electrode and a first spacer is provided. The diaphragm includes a first electret, a second electret, a polymer layer and an electrode layer. At least one layer of the first electret or the second electret is formed by expanded polytetrafluoroethylene. The second electret is stacked on one side of the first electret, while the electrode layer is stacked on the opposite side of the first electret. The polymer layer is made of a hydrophobic material and is disposed on the second electret. The first perforated electrode is stacked on a first spacer and close to the polymer layer. The first spacer disposed to between the diaphragm and the first perforated electrode supports the first perforated electrode over the diaphragm and defines a first chamber. A fabrication method of the electret loudspeaker device is also provided.