12-27-2005 Acoustic Measurements 300 Yards from Exit

At the request of a potential buyer we made acoustic measurement at 300 yards. We had been asked to measure at 300 Meters. We used a laser range finder to determine the distance. It reads only in yards and we did not have yards to meters conversion data with us. We do not think the difference between yards and meters will make a difference in the acoustic reading. To achieve this distance we had to leave the site and climb a hill nearby. Because we were at a higher elevation then the site, and because the jet exits vertically,  the sound level was higher than it would have been at the same level as the site. This was the only location 300 meters away where we could have been level or above the site. The site is approximately 50 feet higher than the surrounding area. At any other location the noise would have been lower as it would have been blocked by the hill or building. We felt this location provided the most honest results. We were approximately 100 feet higher than the site. At this distance the laser range finder we used would only measure to a car in front of the building, and to the AC unit on top of the motor room. This is because most of the reflective objects were angled away from us. Therefore the distance to the center of the jet was estimated and no more accurate than approximately +/- 20 feet. At this distance the sound level would not have varied in 50 feet, so the readings were more or less the same as they would have been at 300 yards or 300 meters from the exit. The distance to the AC unit on top of the motor room was 230 yards. Therefore the distance to the inlet was approximately 232 yards. From this location the compass heading to the site was 155 degrees. The temperature was 59 F, the humidity 34%, and the barometric pressure 29.93. There was no wind. The ambient noise level was higher here because we were in the line of sight of a larger area. The ambient noise was 67.7 db. The 605 RPM noise level was 74.1 db or 6.4 db higher than the ambient noise level. The chart below shows these measurements in detail.

These pictures show the view of the machine from the point of measurement