ATP-3-09-30 Observed Fires Download
Page 171 of 204
Observer Special Missions 28 September 2017 ATP 3-09.30 7-9 ADJUSTMENT BY SOUND 7-34. If observer’s visibility is limited, adjusting fires by the use of sound may be used. The target location may be reported to the observer by the supported unit or the observer may determine it. If the observer can hear noises at the threat position (for example, weapons firing, vehicle or troop movement), the observer can estimate a direction and a distance from the friendly position. The observer must alert the FDC when adjusting by sound. 7-35. Upon hearing the burst of the adjusting round, the observer estimates the direction to the burst and compares it with the direction to the target, then converts the deviation to a lateral shift, in meters (using estimated range to the target). Distance to the adjusting point is difficult to judge; therefore, the observer may have to use a creeping technique to adjust onto the target. The observer can determine distance by measuring the time it takes for the sound to be heard and multiplying the time interval by the speed of sound (350 meters per second). To help the observer determine distance accurately, the FDC must announce the precise moment of impact. 7-36. The observer must use caution in very broken terrain. In hills and mountains, the sound may travel around a hill mass before it arrives at the observer's position and may produce a false direction to the burst.