Context 13:36 Jun 8, 2007
It is a piece from an article in aviation:
Title : 2.NOISE CERTIFICATION TEST AND MEASURMENT CONDITIONS
Content: 2.2.1 Locations for measuring noise from an aeroplane in flight shall be surrounded by relatively flat terrain having no excessive sound absorption characteristics such as might be caused by thick, matted, or tall grass,shrubs,or wooded areas.No obstructions which significantly influence the sound field from the aeroplane shall exist within a conical space above the measurement position, the cone being defined by an axis normal to the ground and by a half-angle 75o from this axis. |