Abstract: Methods and systems for amplitude modulation in a parametric speaker system are provided that perform truncated double sideband (TDSB) frequency modulation of audio signal in which most of the processing is performed in the frequency domain, thus permitting use of fast processing techniques for amplitude modulation (AM) and filtering and reducing computation cost over time domain processing. A maximum envelope value of the time domain audio signal may be to the carrier signal in the frequency domain that avoids emitting the carrier signal when the input signal level is low or mute. The application of the envelope value may be smoothed to reduce discontinuity at input block boundaries.

Abstract: Methods and systems for amplitude modulation in a parametric speaker system are provided that perform truncated double sideband (TDSB) frequency modulation of audio signal in which most of the processing is performed in the frequency domain, thus permitting use of fast processing techniques for amplitude modulation (AM) and filtering and reducing computation cost over time domain processing. A maximum envelope value of the time domain audio signal may be to the carrier signal in the frequency domain that avoids emitting the carrier signal when the input signal level is low or mute. The application of the envelope value may be smoothed to reduce discontinuity at input block boundaries.

Abstract: An apparatus for performing focusing control and tracking control for an objective lens of an optical head of an optical card reader and/or writer including first and second focusing error detecting systems for generating first and second focusing error signals, respectively, first and second tracking error detecting systems for generating first and second tracking error signals, respectively, a circuit for detecting a defect on an optical card to generate a defect signal, a selecting circuit for selecting one of the first and second focusing error signals and one of the first and second tracking error signals in accordance with the defect signal such that the selected error signals are free from the defect, a focusing actuator for moving the objective lens in the focusing direction in accordance with the selected focusing error signal, and a tracking actuator for moving the objective lens in the tracking direction in accordance with the selected tracking error signal.