| 摘要 |
PURPOSE:To automatically make a noise at the time when a noise level from a pillow speaker comes larger, difficult to attract attention by lowering the sound level of a high sound band, outputted from the pillow speaker, when the receiving condition of a sound signal is not favorable and the S/N ratio of the signal is lower than a prescribed value. CONSTITUTION:When the receiving condition is favorable, a signal is distributed so that the sound pressure level of the pillow speaker 9 exceeds the sound pressure level of a vehicle side speaker 8, extending over all sound bands, by a control amplifier 5, and on the other hand, when the receiving condition is not favorable, the signal is distributed so that the sound pressure level of the vehicle side speaker 8 exceeds the sound pressure level of the pillow speaker 9, extending over all the sound bands, by the control amplifier 5. Besides, independently of the quality of the receiving condition, the total sound pressure level at a listening point, that is the sum of the sound pressure levels of both speakers, is set so as to be approximately constant. Thus, a sound field, easy to listen continuously, can be obtained. |
