| 摘要 |
In a method for indicating holes in a wall (1) upon firing at a target having an acoustic chamber (4) which is defined forwardly by said wall (1) and in which microphones (5) are arranged to receive the soundwaves generated by a fired projectile (6) entering said chamber, a quantity corresponding to the sound velocity within the acoustic chamber (4) is calculated on the basis of differences in the transit time of the soundwaves to the microphones (5). The calculated quantity is then compared with a reference value. A hole indication signal is provided when the deviation of the calculated quantity from the reference value exceeds a predetermined value. |
