EXAMPLESSMALL HELICOPTERS

NOISE FOOTPRINTABOVE 62.5 dB

THREE DIFFERENT ALTITUDES

1000’ AGL1400’ AGL2000’ AGL

Altitude(Distance) 1000’

Distance on the Ground = 1732’ or 1/3 Mile

Distance – 2000’

Average Noise Levels on the Ground69 dB* 62.5 dB

HELICOPTER ASSOCIATION INTERNATIONAL (HAI)DISTANCE/NOISE RELATIONSHIP

*HAI GENERAL RULE:IF THE DISTANCE IS HALVED,THE NOISE IS INCREASED 6-7 dB

From Noise Tests

AVERAGE HALF-FOOTPRINT OF NOISE ABOVE 62.5 dB

Estimated

2

HELICOPTER AT 1000’ AGL – AVG FOOTPRINT NOISE ABOVE 62.5 dB– 2/3 MILE WIDE (At 60 dB noise begins to interfere with speech communication)

CutCorner

CutCorner

Agreed Path

3

NOISE

Altitude(Distance) 1400 ‘

66.4 dB

Distance – 2000’

AVG HALF-FOOTPRINT 1428’ or 1/4 Mile

62.5 dBAverage Noise Levels on the Ground From Noise Tests

ROBINSON HELICOPTER CO. FLIGHTS AVERAGED 1400’ AGL. INCREASING THE ALTITUDE FROM 1000’ TO 1400’ REDUCES NOISE DIRECTLY BELOW AND REDUCES THE 62.5 dB FOOTPRINT FROM 1/3 MILE TO 1/4 MILE.

RESULTS OF INCREASED ALTITUDE

4Estimated

HELICOPTER AT 1400’ AGL – AVG FOOTPRINT NOISE ABOVE 62.5 dB – 1/2 MILE WIDE (At 60 dB noise begins to interfere with speech communication)

CutCorner

CutCorner

Agreed Path

5

NOISE

Altitude(Distance) 2000’

62.5 dB

AT AN ALTITUDE (DISTANCE) OF 2000’ THE AVERAGE FOOTPRINT IS 6.52 dB DIRECTLY BELOW THE HELICOPTER.

RESULTS OF INCREASING ALTITUDE

6From Noise Tests

HELICOPTER AT 2000’ AGL – AVERAGE NOISE FOOTPRINT 62.5 dB

7

NOISENOISE