5.24 Vibration (V)
exceeds 120 dBP (unweighted peak decibels). However, structural damage is
not likely to occur until a level of 150 dBP is achieved.
Vibration is an oscillation or motion that alternates in opposite directions and
may occur as a result of an impact, explosion, noise, mechanical operation, or
other change in the environment. Vibration may be caused by military and /
or civilian activities.
Areas of military overflight cover an area traversing several counties, and
numerous cities, towns and communities, elevating the possibility for
vibration‐related complaints across a broad area or northeastern
North Carolina. Low level flight is normally conducted along specified MTRs
throughout this region, producing noise and in some cases vibration.
Seymour Johnson AFB controls six MTRs throughout the DCR JLUS Study Area
while other branches of the Armed Forces control seven MTRs. These MTRs
are illustrated on Figures 3‐13 and 3‐14 in Chapter 3. The minimum flight
operating floor in the MTRs controlled by Seymour Johnson AFB is
500 ft. AGL.
ISSUE
V‐1
Vibration Impacts from Low‐Level Flight Activity
Vibration from low‐level fixed‐wing and rotary‐wing
aircraft overflight in Restricted Areas, Military Operating
Areas and Military Training Routes has the ability to
cause physical property damage.
Within the northeast North Carolina region are also Restricted Areas and
MOAs which are under the control of both Seymour Johnson and other
branches of the Armed Forces. These airspaces are illustrated in Figures 3‐9
and 3‐11 in Chapter 3. Restricted Areas have variable minimum operating
floors ranging from surface up to 1,000 feet MSL, while MOAs typically have
higher minimum floors ranging from 6,000 feet MSL to 15,000 feet MSL with
the exception of the Stumpy Point MOA – off the west coast of mainland
Dare County east of the DCR with an operating floor of surface. The
operating altitudes of these Restricted Areas and MOAs are illustrated in
Figure 5.24‐1.
Compatibility Assessment
The relationship between sound and vibration is inextricably linked since
vibration is the pressure wave usually accompanied by sound (noise) and
amplified in the lower frequency ranges. While numerous studies have been
conducted to quantify the impacts of noise, very little research has been
conducted to correlate vibration from low frequency sound and human
response. One common conclusion across studies is that as the frequency
decreases, the degree of annoyance or state of irritation from the noise and
vibrations increases more rapidly with sound pressure level. A low‐frequency
signal can go from being audible, to annoying, to oppressive and vibrational
with a relatively small change in level and it is not absorbed by the
atmosphere or blocked by terrain and buildings as effectively as higher
frequencies.
Studies have been conducted regarding the potential for structural damage
resulting from vibration. Homeowners typically become concerned about
structural damage due to the rattling effect when sound that causes vibration
Background Report
Page 5.24‐1