wild guide: sound underwater
THE RESULTS
TEST 1
subject: ANCHOR
- surface splash
TEST PARAMETERS
The various tests were carried out in a
small quiet bay of the Rivière des Prairies in
Laval. It is obvious that a water containing
a lot of suspended matter slows down
the propagation of the sound. However,
these conditions are normal for everything
related to the St. Lawrence River corridor
from Cornwall to beyond Quebec. If you
visit and exploit crystalline water bodies,
I suggest you increase the results obtained
in this test by 25%. If the water is only
slightly tinted, adjust it with a 10% or 15%
change. What is important to remember is
the overall result and remember what may
disturb the fish or not.
After donning all his dive gear and
bottle, Daniel launched himself into the
water. However, he did not wear a hood,
which would have covered his ears and
thus obstructed his hearing. Moreover,
between each sequence, before he was
ready to hear and evaluate a sound, he
stopped breathing under water so as not to
pressure his regulator.
The procedure was fairly simple. We
had 25 different sounds that we wanted to
evaluate. At first, Daniel would be 5 feet
deep, at a 45-degree angle with the boat,
so 5 feet away, under water. We would do
all these tests 10 feet deep at a 45-degree
angle to the craft, so 10 feet away, then
20 feet, always in a perpendicular axis at
45 degrees, which is a distance of 20 Feet
with the boat. So, the deeper we dived, the
farther we were from the point of origin of
the sounds. The last test would be 20 feet
deep, but this time directly under the boat.
The latter survey should be of particular
interest to lovers of verticle fishing. All
this meant that my diver was to evaluate
25 sounds, in four different depths and
positions. So we would have 100 results.
Our methodology consisted of making
Daniel dive deep down. When I no longer
saw air bubbles rising to the surface, I
knew he was ready. Before I made a noise,
I hit two good shots on the floor of the
boat. After this was executed, I waited
for 5 seconds. Then I gave two more good
moves before doing the same operation
again. After hearing four noises, he went
up to the surface and explained what he
had heard. Thereafter, he awarded them
a score out of 10. The score of ten being
a quite nasty noise and the score of zero
being an inaudible result.
Fishermen are often seen throwing their
anchors a distance from their boats. We
wanted to know if the sound of the anchor
smashing the surface of the water was
very noisy. So we launched an 18-pound
anchor, attached with a 6-foot length
chain and a regular nylon rope. Within 5
feet of depth, surface noise was among the
strongest. It reached the score of 5/10. This
score went down to 3 when Daniel was 10
feet away, then to 1/10 at 20 feet. When it
was in 20 feet, directly under the boat, the
rating rose to 2.5 /10. It is therefore easy to
imagine all the crash that this causes and it
can be said that it certainly scares the fish
in the vicinity. You’d better deposit your
anchor instead of throwing it off. TEST 2
subject: ANCHOR - seabed landing
This experiment was a logical sequel to the
first test. As soon as the diver had heard
and assessed the “splash” on the surface,
he had to wait until the anchor crashed on
the seabed after its free fall. The scores were
as follows: 5 feet, 3/10. At 10 feet 3/10 and
at 20 feet 1.5/10. This last note may sound
strange to you, but you should remember
that the further it descends, the farther it
gets away in a 45-degree angle. You will not
be surprised to learn that directly under the
boat, in 20 feet of depth, the note is raised
to 3/10. You should also know that the
bottom where we were was rather muddy.
If the latter had been made of stone or rock,
the results would have been much more
intense. Take the precaution lower your
anchor slowly into the abyss.
5 FEET 5 FEET
10 FEET 10 FEET
20 FEET 20 FEET
20 FEET 20 FEET
TEST 3
subject: LURE - surface strike
We all catch weeds with our lures from time
to time. Some fishermen have the very bad
habit of whipping their lure violently on the
surface of the water to remove them. This
shock usually has the effect of releasing the
weeds, but how loud is it under water? We
used a swim bait and hit it several times on
the surface of the water. To be truly frank
with you, I hate when my guests do that. I
was really looking forward to the results so I
could say that I was right or I would be called
grumpy. In 5 and 10 feet of depth, Daniel
estimated 2/10 sound impact. In 20 feet at a
45-degree angle and directly under the boat,
that’s down to 0.5/10. The impact is much
less, but it does indicate that we’re there.
As for the depths of 20 feet or more, I must
proclaim loud and clear that I may be a little
grumpy, but that I was quite right anyway.
5 FEET
10 FEET
20 FEET
20 FEET
Wild Guide
. Fall 2017
46