The invention features a dual-mode audio system for an automobile which in one mode is configured for play while the doors to the automobile are closed, and in a second mode, is configured for play while a door, such as a tailgate, is opened. Additionally, the invention also features a battery monitor which monitors the operating condition of the battery and may estimate the energy capacity of the battery. The system may also take power conservation measures if the system determines that the engine is not running or the operating condition of the batter reaches a predetermined state. The invention also features a remote control integrated within a key fob for controlling the audio system. The invention features various orientations for mounting a pair of loudspeakers within an automobile which directly radiate sound out of a rear opening of the automobile.

Automobile Audio System

A multi-dimensional audio processor receives as an input either a single channel signal or a two channel signal from an audio signal source; for example a musical instrument or an audio mixer. The processor is programmable to divide the input among at least 3 output channels in a user-defined manner. The processor is also user programmable to provide a variety of effect and mixing functions for the output channel signals.

Multi-dimensional processor and multi-dimensional audio processor system

A surround sound encoder, intended for implementation in software, runs in real time on a personal computer using low mips and a small fraction of available CPU cycles. In the principal application for the encoder, the Lt and Rt signals of the encoder are mixed with the Lt and Rt signals of a pre-recorded source (e.g., computer game soundtrack, CD ROM, Internet audio, etc.). Alternatively, the encoder may be used by itself or with one or more other virtual encoders to provide a totally user-generated soundfield. The encoder is implemented in either of two ways: the signal being encoded may be panned to one or more of the four inputs of a surround-sound fixed matrix encoder or the signal may be encoded by applying the signal to a surround-sound variable-matrix encoder. Phase shifting, required in the encoder, is achieved by applying a signal to two phase-shifting processes, producing two signals whose relative phase difference is sufficiently close to the desired phase shift over at least a substantial part of the frequency band of interest. Satisfactory audible results may be achieved, using very low computer processing power, when one of the phase shifting processes is implemented by a first-order all-pass filter and the other phase shifting process is implemented by only a short time delay, which also has an all-pass characteristic.

Audio matrix encoding

An apparatus (10) for realistically reproducing sound, particularly for sound based on a stereophonic signal having dialog and effects and associated with an accompanying video image. The apparatus includes a front speaker (20) located in proximity to the video image for providing acoustic output based upon a summation signal of the component left and right (L+R) channels of the audio signal. A rear speaker (26) located to the rear of the viewing area provides acoustic output based upon a difference signal, (L-R) or (R-L), between the left and right channels. Left and right speakers (22 and 24) are located to the respective left and right sides of the viewing area. The left and right channels speakers (22 and 24) reproduce in one embodiment the respective left and right channels of the audio signal and in a second embodiment reproduce a difference signal, (L-BR) or (R-BL), where B is a gain which may vary or may be a value fixed between zero and unity. Output to the left and right speakers (22 and 24) is band limited to substantially filter out frequency components below a predetermined threshold. A bass speaker (18) may also be provided to output the low frequency components of a (L+R) summation signal. The (L+R) summation signal input to the front speaker assists in localizing dialog to the video image. The (L-BR) or (R-BL) difference signal substantially removes dialog sound so that the side and rear speaker output primarily comprises sonic ambience and surround sound effects. Band limiting the left and right speakers further assists in localizing dialog to the video image. Alternatively, in yet another embodiment, a monophonic signal may be applied to at least one embodiment of the system to enable production of a spatially enhanced surround sound effect.

In-home theater surround sound speaker system

An output audio signal (L, R) is generated based on an input audio signal, the input audio signal comprising a plurality of input subband signals (N). The input subband signals are delayed in a plurality of delay units (76) to obtain a plurality of delayed subband signals, wherein at least one input subband signal is delayed more than a further input subband signal of higher frequency, and wherein the output audio signal is derived (77) from a combination of the input audio signal and the plurality of delayed subband signals.

Audio signal generation

A filter network for use with an acoustic signal reproduction system having at least two, spatially separable, speaker means each capable of reproducing acoustic waves from corresponding electrical signal. The network includes a frequency divider for separating an electrical signal representative of acoustic waves into first and second components, the first component including primarily those audio frequencies, which when acoustically reproduced tend to provide unambiguous binaural phase localization. The second component includes primarily those audio frequencies which when acoustically reproduced tend not to provide unambiguous binaural phase localization. The network also includes structure for delaying the first component for a predetermined period of time to produce a delayed signal so that when the combined first and second components are applied to one of the speaker means and the combined second component and the delayed signal are applied to the other of the speaker means the acoustic field produced tends to simulate spaciousness or ambience of a larger room than the actual listening area.

Robert A. Berkovitz

Papers

Auditorium simulator economizes on delay line bandwidth