Abstract: An apparatus for expanding a sound image upward includes a left-channel phase delay circuit for correcting phases and amplitudes of components of an input left-channel audio signal which are in a predetermined high-frequency range to generate a corrected left-channel audio signal. A right-channel phase delay circuit operates for correcting phases and amplitudes of components of an input right-channel audio signal which are in the predetermined high-frequency range to generate a corrected right-channel audio signal. A surround circuit operates for generating left-channel and right-channel surround audio signals in response to the corrected left-channel and right-channel audio signals generated by the left-channel phase delay circuit and the right-channel phase delay circuit.

Abstract: A phase-conversion surround circuitry gives surround effects to right- and left-channel audio signals. An audio difference signal between the right- and left-channel audio signals is delayed at a specific time constant. The delayed audio difference signal is combined with the right- and left-channel audio signals, thus composite audio signals being generated. The time constant is periodically varying under oscillation at frequency of 12 Hz or less.

Abstract: A phase-conversion surround circuitry gives surround effects to right- and left-channel audio signals. An audio difference signal between the right- and left-channel audio signals is delayed at a specific time constant. The delayed audio difference signal is combined with the right- and left-channel audio signals, thus composite audio signals being generated. The time constant is periodically varying under oscillation at frequency of 12 Hz or less.