Abstract: An active noise cancellation (ANC) system may include an adaptive filter divergence detector for detecting divergence of the one or more controllable filters as they adapt, based on dynamically adapted thresholds. Upon detection of a controllable filter divergence, the ANC system may be deactivated, or certain speakers may be muted. Alternatively, the ANC system may modify the diverged controllable filters to restore proper operation of the noise cancelling system.

Abstract: The present disclosure relates to systems and methods for active sound management for vehicles. In one embodiment, a process for active sound management for a vehicle includes determining vehicle operation state and powertrain operation for the vehicle, and detecting sound generated by the powertrain operation of the vehicle. A synthesized sound may be determined for output based on selection of at least one frequency of the sound generated by the powertrain to drive a frequency of a sine-wave generator, synthesizing an output wave file with pitch shifting of frequency based on powertrain operation, and blending sine-wave generator output with the synthesized wave file to cancel unwanted powertrain noise and generate desired sounds for vehicles. Output of the synthesized sound may be controlled to provide simultaneous cancellation and synthesis in at least one same frequency range.

Abstract: A method for operating an internal combustion engine. The method includes: providing a functional relationship between time rate of change in engine speed, and compression ratio switching engine speed limit; determining time rate of change in engine speed; determining from the determined rate of change of engine speed and the function whether the engine speed exceeds the compression ratio switching engine speed; and commanding the engine to operate at a relatively low compression ratio if the determined time of change in engine speed exceeds the compression ratio switching engine speed limit and commanding the engine to operate at a relatively high compression ratio if the determined time of change in engine speed is less than the compression ratio switching engine speed limit.

Abstract: A method and system for operating an internal combustion engine. The internal combustion engine is operable in a plurality of compression ratio operating modes. The method includes determining a relationship between a base engine threshold load where the high compression and low compression provide substantially the same engine fuel consumption and engine speed. The determined nominal relationship is modified by a factor, such factor being a function of a condition under which such engine is operating, to obtain a modified relationship. The modified relationship is a function of engine speed and the condition has an effect on knock generation in such engine. The modified relationship and engine speed are used in selecting one of the plurality of compression ratio operating modes for the engine.