1979 年 35 巻 10 号 p. 554-561
This paper presents a new method for the field measurement of short-range sound propagation. It is based on the correlation method, and uses a coherency recovering means which detects fluctuation in the propagation time and synchronizes a transmitted signal to a received one with the aid of a pilot signal. The pilot signal is radiated together with the test signal, and at a receiving spot, it is extracted from the received signal. Then, it is converted to a clock pulse train by which a new signal similar to the test signal is generated. Since this signal contains the same fluctuation as the received one, it becomes possible to take cross-correlation between them coherently, and the measured correlation function represents sound propagation characteristics. This paper also presents an inverse-filtering method for compensating frequency responses of acoustic instruments used in the measurement. Theoretical considerations for the properties of the system which has a statistically fluctuating response are also made. A device utilizing the methods said above is made with a micro-computer, and the experimental results show the effectiveness of the methods.