A loudness control circuit emphasizes low frequency components in audio signals. A secondary low-pass filter select low frequency components of the audio signals, inverting a phase of the audio signals. The phase-inverted signals and audio signals are respectively inputted to an inverting input terminal and non-inverting input terminal of an operational amplifier to obtain audio signals whose low frequency components are emphasized. These signals have the same phase as the phase of the inputted audio signals. The output of the low-pass filter is amplified to obtain a signal having low frequency components whose phase is inverted. Both the audio signal whose low frequency components have been amplified and the low frequency components whose phase has been inverted are applied to a speaker to reproduce sounds with their low frequency components dynamically emphasized.