| 摘要 |
PURPOSE:To secure a speaker with a proper level in sound volume which are set in a station yard, etc. in response to the level of noise and at the same time to reduce the deterioration of the sound quality, by providing a band eliminator, band extractor, band variable switch and a deterioration detector respectively. CONSTITUTION:Only the component from which many frquency bands are eliminated by a frequency band eliminator 7 is delivered through a speaker 4. A frequency band extractor 8 extracts said eliminated frequency component. That is, the sound frequency component of the speaker 4 is not contained in the output frequency component of the extractor 8. Here a sound volume controller 2 is actuated with the frequency component of the extractor 8 and controls the speaker output. While a band variable switch 9 varies the frequency bands of the eliminator 7 and the extractor 8 to minimize thesound deterioration. In this case, the deterioration is caused for the output sound. Thus a deterioration detector 10 controls the switch 9 to detect and set the switch position where the sound deterioration is minimized. Both a high-speed Fourier conversion (FET) and an inverse high-speed Fourier conversion (IFET) processors are used to the eliminator and the extractor 8 respectively. |
