Conversion Delay-Distance And Distance-Delay; Notions Of Trigonometry; Air Attenuation - PROEL AXIOM - VERSION 2.0 Manual

C.3. CONVERSION DELAY-DISTANCE AND DISTANCE-DELAY
C.3 Conversion Delay-Distance and Distance-Delay
When the speed of sound is known, the relationship between time delay t in milliseconds and distance
d in meters can be expressed be the following:
C.4 Notions of Trigonometry
Sometimes it is not possible to use measurement tools such as laser range finders. In these situations
it is still possible to derive necessary distance measurements from simple measurements taken with a
tape measure.
The distances to measure (in meters) are H , L and d
value of H and the mounting details from the LAC software.
The value of d
SAT
From this result, one can then calculate the difference in sound path length between SUB and SAT
and, consequently, the delay (in seconds) to input to the processor:
C.5 Air attenuation
The air introduces a notable attenuation at high frequencies. This attenuation is fundamentally a function
of the relative humidity and expressed in dB/km. In the case of sound projection over very long distances,
the total attenuation can be very high.
t = 1000 ·
is given by:
d
SAT
∆ T =
d
[ ms ]
c
t · c
d = [ m ]
1000
. The value of h easily be obtained from the
SUB
√
∼ =
2 2
L + h [ m ]
− d
d
SAT SUB
[ s ]
c
102
C. Useful Formulae and Tables