| 摘要 |
PURPOSE:To unnecessitate a concave mirror for collecting sounds and to easily obtain sound collecting ability by delaying phases by phase delay circuits respectively connected to plural speakers and making signal phases coincident at one point on a space. CONSTITUTION:A phase delay circuit 5 is composed of an A/D converter 6, memory 7, D/A converter 8 and amplifier 9, and an audio signal is modulated to a digital signal by the A/D converter 6, held in the memory 7 for fixed time, afterwards, demodulated to an analog signal by the D/A converter 8, amplified by the amplifier 9, uttered by a speaker 2 and delayed. This phase delay circuit 5 is provided corresponding to the plural speakers 2 and operated so as to arrange the phases of sounds at a hearing position 4. At the hearing position 4, the sounds are heard loudly by adding amplitudes since signals coming from the respective speakers 2 arrange the phases and at any position excepting for the hearing position 4, the sounds are slightly heard since the phases of signals are not always arranged and the amplitudes are not added. |
