In the present embodiment, the heat generating layer 20 includes a fiber with at least a partial metal coating on a surface thereof. Therefore, the surface area in contact with air is increased, and the sound pressure is improved. By applying the metal coating to the fiber, the electric resistance of the heat generating layer 20 can be set to an appropriate value according to the adjustment of a coating film thickness and selection of a coating material.

Moreover, the fibers can be arranged directly on the support 10 or can be arranged via an adhesive layer, such as a polymer material.

FIG. 2 is an electron micrograph illustrating a surface of the heat generating layer 20. Hereinafter, a case where the fibers are in the form of a nonwoven fabric that is not woven but is bonded or intertwined by thermal, mechanical or chemical action into a sheet shape will be described. In an exemplary aspect, a metal coating is applied to the surface of the fiber.

According to exemplary aspects, the heat generating layer 20 can be in the form of such a nonwoven fabric, can be in the form of a woven fabric in which warps and wefts are combined, can be in the form of a knitted fabric in which fibers are knitted, or can be in the form of a mixture thereof.