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Appendix 4 . Sound Measurement Data taken of the Boeing Vertol 107-II at Hook Points during a Timber Sale in Detroit, OR (October 17, 2007).

Background. After the initial measurements were taken in the Spring of 2007 at the Log Landings (as reported in Main Report, this study), we decided to take, at least, a few measurements of a helicopter performing logging operations at Hook Points to document whether or not there was a difference between the helicopter noise generated at the Long Landing verses helicopter noise at the Hook Points. (For a discussion of "Hook Points", see Main Report, page 5.)

Methodology. The methodology used to record sound levels at the Hook Points was identical to the methodology used for the Log Landings as described in the Main Report (see Main Report, Section 4), except that only two technicians recorded sound and technicians were positioned along an existing trail (not in line with the sound source).

Study Area and Helicopter. The study area was a US Forest Service, ( Willamette National Forest, Detroit Ranger District) timber sale just north of Detroit, OR. ( Marion County, T9S, R5E, sections 35 & 36, Willamette Meridian.)

Oregon State map showing the location of Detroit, OR

Map showing the location of where sound measurements were taken on Detroit Timber sale.

Locations of the 2 sound recorders and 4 Hook Point locations.

The sale was harvested by Columbia Helicopter using their Boeing Vertol 107 to extract timber. A 200-250' drop line was used.

The forest vegetation on the study area was similar to the Cedar House and Moon 25 timber sale area in the Main Report. Sound measurements were taken on 17 October 2007 from approximately 9am until about 1pm.

The weather on the day of sound measurement was dominated by a constant drizzling rain. The average temperature was 56-57 o F; the humidity was about 87%; the barometric pressure was 27.7 inHg (inches of Mercury); and it was essentially a windless day.

Hook Point site on Detroit Timber sale. Recorders were positioned along jeep trail.

Columbia Helicopter's Vertol 107 retrieving a log load from a Hook Point.

Results. The sound levels recorded at various distances from the helicopter while it performed normal operations at Hook Points are below.

The average of the maximum noise levels at a given distance is displayed below. (Since only a few measurements were taken per given distance, calculating a standard deviation statistic was considered meaningless.)

Click on image for larger view.

The average maximum readings of noise level of the Vertol 107 at a given distance from the Hook Points is very similar to the average maximum values obtained for the Vertol 107 at the Log Landings. The above graph is nearly identical to Figure 5a of the Results Section. No significance determination can be made; however, as the sample size of the Hook Point data is small. But even with just the few measurements taken, this data suggest that the helicopter noise level during operations at the Log Landings is very similar to the noise level at the Hook Points.