The light emitting structure disclosed includes a light emitting device, a metal frame, and a repressing fastener. The audio processing unit a signal enhancer for enhancing an m-channel signal part of the n-channel input signal, where m<n, the signal enhancer having, for each channel signal part of said m-channel signal part, a non-linear anti-symmetric monotone transfer function. The method determines a suitable filtering scheme using a correspondence relationship between the filtering scheme and keywords and user-characteristic data. A reference APD also biased in a breakdown region in a Geiger mode is optically shielded from light and outputs a voltage that is measured by an analog to digital converter. In one embodiment, the SAW device includes: a piezoelectric substrate, a conductive layer located over the piezoelectric substrate and a resistive layer, interposing a portion of the conductive layer and the piezoelectric substrate, that forms a return path for static charge migrating from the piezoelectric substrate to the conductive layer. The semiconductor structure includes a first electrode layer, a second electrode layer and a dielectric layer between the first electrode layer and the second electrode layer.