| 摘要 |
PURPOSE:To test and evaluate a sound transmission line on characteristic conditions close to actual room acoustic characteristics without the limitations of time and a place, by providing a circuit group which generates an artificial echo signal. CONSTITUTION:The noise generator 81 of an interior noise generation part 8 generates a white noise, which is passed through a filter 82 having such frequency characteristics that the attenuation from a low frequency range to about 3KHz increases linearly by 5dB at every interval of one octave, setting the level of a Hoth spectrum noise signal to a desired value. An A/D converter 61 of a filter part 6 samples an analog receive signal at specific intervals of time and sends the sampled signal to an adder 9 through a filter 62 and a D/A converter 63. The adder 9 adds an artificial echo signal from the filter part 2 to the Hoth spectrum noise signal from the room noise generation part 8 and sends the sum signal to a terminal 3, so a sound transmitter 10 is tested and evaluated by the conditions close to actual conditions. In the filter 62, an adder 64 sums up outputs of the tapped delay circuit consisting of cascaded delay devices D11-D1n through coefficient multipliers 20-2n. |
