Analysis and Ranking of the Acoustic Disturbance Potential of ...

Report No. 6945
BBN Systems and Technologies Corporation
Reflection Loss (RL)
The reduction in sound level after reflection from an absorptive
surface, expressed in logarithmic terms
where Lref and Lint are the reflected and incident sound levels at 1
m from the reflection point.
Sound Level or Received Level, Lr
The sound pressure at an observation position expressed in
logarithmic terms
LR = 20 loglO p/Pr (dB)
where the reference pressure, Pr = 1 microPasca1 (vPa)
Sound Speed Profile
The variation of the speed of sound as a function of water depth.
Sound Wavelength, X (m)
1 = c/f, where c is the speed of sound (m/sec) and f
is the frequency (Hz).
Source Directivity, D
The change in acoustic output of a source as a function of aspect
angle in both the horizontal and vertical plane. Generally expressed
as a logarithmic ratio
where p is the pressure in a given direction and Pm is the maximum
source pressure in a reference direction.
Source Level, Ls
The sound pressure at an observation position 1 m from an acoustic
source (dB re 1pPa at 1 m)
Spreading Loss
The reduction in sound level caused by
spreading of sound
energy, generally expressed as cylindrical spreading (10 logl0 range)
or spherical spreading (20 log range).
Time Ratio or Duty Cycle
The ratio of the total effective operating time in an operating cycle
or in an exposure period, whichever is shorter, to the length of the
cycle or period for a specific source.