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Entries in Hydrophone (3)


Swarming Minnows

Recently I took a weekend trip up to visit some friends at their cabin outside the city.  It’s always great to get out of the concrete and glass of my daily surroundings and hit the lake.  This particular weekend was during a recent heat wave and it was great to be in nature where the temperature was a little cooler.  My friend’s cabin is in a bay with a lot of variation in the water level, causing a big difference in where the shore line will be at various points in the year. In order to combat this the docks have to be built reaching quite a way out into the water to ensure that the boats will not hit the bottom during low season.  Their dock stretched out into the water about 100 feet (as seen in photo above) and made a great place to sit and spend an afternoon lounging and passing the time.  While out on the dock I noticed that hundreds, maybe even thousands, of 2 inch minnows were huddled under the dock, possibly to use the shade as protection from the blasting mid-day sun.  This made me wonder if these little fish made any noise as they whipped around each other in such tight quarters, so I grabbed my hydrophone and dropped it in the water to take a listen.  

I quickly found out that the minnows wanted nothing to do with the shinny silver capsule of the hydrophone. The second it hit the water they all uniformly swam away a few feet and kept their distance from the intruder.  Luckily I was doing nothing for the rest of the day but relaxing, so my plan was to simply wait them out.  I figured if I left the hydrophone in the water for a long while the fish would start to accept it as part of the environment and eventually start swimming near it and then I could listen in.  As time past I came to the conclusion that this was not going to work.  After a long time they were still going no where near the underwater microphone.  At this point my wife asked me what the hell I was up to, somewhat annoyed that I was doing work-esque experiments at a beautiful lake instead of just relaxing.  Luckily she knows me well enough to realize that this is my form of relaxing.  So when she heard my situation she immediately came up with the answer to my problems.  I had to lure the fish in towards the mic, but I still did not know how, until she told me fish eat bread.  What?  Fish eat bread?  I had no idea, and to be honest I was very skeptical of this even being true.  Until I tried it and found out it is 100% true.

I poked a hole in the middle of a slice of bread, fed the cable for the hydrophone through the hole and then popped the little audio trap in the water.  I had to put the cable through the bread hole in order to keep the bread slice from floating away on me.  Next I tied off the cable on the dock so the length had the capsule of the hydrophone about an inch to two below the bread in the water.  This time I did not have to wait long for the minnows to come over and investigate.  With in a minute I had about 5 or 6 minnows taking little pecks at the bread and although it was cool to watch it even cooler to listen to.  The little fish made great little wiggle sounds as they moved around the mic.  Take a listen:

Hydrophone Recording of a Few Minnows Eating Bread Underwater by azimuthaudio

Then in another minute a whole other school of fish came over for a taste and then another wave of the little wigglers came after that.  Soon there were hundred and hundreds of the tiny fish swimming all over the area near the bread slice, taking little bites. The sound of them all together became a lot more delicate and clicky.  The sounds they were making were mostly the sounds of tiny little bites into the bread as they slowly nibbled away, sounding kind of like a wet static.  There were also some sounds of their little tails whipping the capsule as they swam by.  There were also other noises that I am not able to easily identify (listen to the video a few paragraphs below).

 As time passed the fish were really putting a dent in the bread.  First they ate their way through the crust and then worked on the interior until they managed to eat enough bread to free it from the cable of the hydrophone. Finally the slice was taken away with the current while the fish follwed it. The whole sequence lasted about 40 minutes.

The fish were causing such a commotion even a crawfish came out of hiding to see what was going on.
Here is a video of the experiment.  It starts off showing what the bread trap looked like and how the fish were around in the water but basically ignoring it.  Then when the camera re-enters the water there is an edit to about 15 minutes later when the fish were eating up a storm.  The sound over the whole video is from when the bread was under siege by hundreds of nibbling fish.  
As you can tell it never got very loud and also never got too swishy as the fish whipped around the mic.  It is nothing like I expected the fish to sound like, but I still think the fragile texture of it is amazing.  
At times bunching of the fish around the bread was so dense you could barely even see the hydrophone sitting in the water.
Once again I have to thank my wife for helping me out with both the bread idea and for taking the pictures and video.  It turns out she is not a bad catch after all.



Waterfall Bouncing and Hydrophone Review 

About 6 months ago I ordered an H2a-XLR hydrophone from Aquarian Audio, but because of the frozen weather during the Canadian winter and my busy work schedule through the spring I hadn't really had a chance to put it through its paces. I recently found myself with some time to kill on a sunny Saturday so I decided I would take out the hydrophone and see what I could capture with it. I went out to a dirt road way north of the city and found a great spot to experiment with underwater recording.

First I put the hydrophone in the water at the edge of a river, behind a pile of rocks, so the mild current of the river would rush over the rocks and over the submerged microphone. It did not make the sound I was expecting but it was an interesting sound all the same.  Here is a video clip with the audio feed from the hydrophone and footage of the camera going underwater.

Next up I found a spot where a small feeder stream had been re-routed to make room for a road that was built across its path.  The stream fed into 2 large corrugated steel culverts passing under the new road.  At the downstream end of the culverts the water tumbled out and created a small waterfall about 8 inches high.  


My plan was to place the hydrophone about a foot away from the base of this little waterfall to see what I would get.  I climbed up on top of one of the corrugated pipes and sat down with my legs hanging over the opening and started getting the gear ready to record.  While I was untangling some cables I was unintentionally dipping the hanging hydrophone into the tiny waterfall.  The current of the water was pushing the hydrophone out of the water flow and the mic would swing like a pendulum out into the air a bit and fall back into the stream of water, only to be pushed out again by the current.  Each time the capsule hit the current it would make a weird "splosh" sound followed by a sound almost like a backwards splash as it was boosted back out of the current.  

I quickly changed my plan and hit record to capture this sound.  I found I could change the sound a lot based on how hard and fast I let the capsule hit the water.  The sound this maneuver produced was extremely loud and if I gave the mic anything more than a gentle swing the limiters on my recorder would kick in fairly hard.  At first I was trying my best to avoid this, but after some experimentation I realized the limiters were helping to shape some of the unique sounds I was getting - so I just went with it.  Here is a video that can better explain how I was creating the sounds. 

With some tight editing, EQ and gating I've minimized the sound of the waterfall before and after the capsule impacts, creating isolated sploshes, splashes and soggy impacts.  I cut together a few of the different kinds of sounds I got in sync with the above video.

All this was working out great until the black flies found me and started taking big bites out of me.  One got my foot while I was recording and while wildly trying to kick it away I instead kicked off my shoe, which went floating downstream.  I managed to rescue the shoe but I had to slog my way back to the car with a soaker that lasted the rest of the day.  But before I left I did grab a quick recording of the stream just beyond the little waterfall.

 Take a listen: Hydrophone 1ft past 8inch Waterfall by azimuthaudio


Aquarian Audio H2a-XLR Mini Review

First I should be clear up front and say that this is the only hydrophone I have ever used, so I have nothing to compare the H2a against.  I have found it to be a great product so far.  I was pretty sure I was going to be happy with it as I did a fair bit of research on it before I purchased it and all the reviews I read were glowing.  

One of my first observations was that this mic is sturdy.  In my initial experiments with it I was tossing it into rivers but overestimating the depth of the water, so the capsule hit rocky riverbed fairly hard more than once. The H2a seemed no worse for wear.  It's heavy enough that it can sink into the water and sit still - it seems to have the perfect ratio of weight vs being too heavy and cumbersome.  

As you can hear in the recordings above, the sound it captures is quite bright. I was initially surprised by this, since I was half expecting that cliché 'underwater' sound that's all low-end and heavy. Apparently not the case: there's plenty of high frequency sounds to be heard. According to the specs, the H2a picks up frequencies from 10Hz to over 100kHz, so I stand corrected as to what it really sounds like down there. 

Aquarian Audio offers a surprising and useful accessory for the H2a: a Contact Mic Adaptor that turns the hydrophone into a contact mic, and a really good one at that.  The adaptor is a little rubber cup with a flat bottom. You slide the H2a into the cup and then place the flat part on any surface... and you've got a fantastic contact mic with almost no noise floor.

All this for under $200 (US) including the adaptor.  Now that's bang for your buck.  The fellow who runs the company seems really invested in his products; when I ordered mine online I got a phone call soon after from the owner, who wanted to go over my order to make sure I was getting the right product for my purposes. Apparently they sell a lot of these mics to sound recordists as well as to marine biologists, and he wanted to be sure I was using it for SFX gathering - since the length of cable I ordered would not be suitable for scientific studies.  

All in all I am very happy with the H2a.  The quality you get for this price is a pretty fantastic deal.



Underneath the Ice

In the dead of winter I was up up north staying at a family cottage and on the second day I was there it was extremely warm.  Well, extremely warm for northern Ontario in January, the temperature popped up above zero and the sun was out in full force.  The river was frozen solid but the full day of warmth melted a layer off the ice leaving about an inch of water on top.  Then when night fell the temperature changed quickly and severely as a cold front entered the area, plummeting everything back far below zero in what seemed like just a few minutes.  In these situations the ice makes crazy sounds as it freezes and shifts.  I was hoping to get out on the lake and get some stereo recording of these sounds but the wind was just too unforgiving and even with my blimp the wind noise was too loud to get any usable recordings of the ice.  But luckily I had brought my Hydrophone, underwater microphone.

After everyone else had gone to bed, I headed out on to the frozen river looking for a crack I could drop the hydrophone into, hoping that maybe I could get some of the huge ice shifting sounds from underneath and avoid the wind altogether.  The ice was very thick, more then 6 inches, so it took lots of roaming around in the pitch black night, before I found a good crack with a small hole just barely big enough to get the hydrophone through and immediately found I could hear some crazy sounds. 

This is a picture of the crack in the ice with the hole and the hydrophone's cable coming up out of the ice.


I was hoping to get big, low end booms of the ice cracking but what I ended up getting was the opposite, tiny sounds of the water in the immediate area of the microphone cracking and popping as it froze.  I left the hydrophone in the ice for about 45 minutes and got a whole lot of silence but here is a clip of about 8 different sections where the ice came to life with crackles and pops.

I also took some time to grab some blocks of ice near the shore and smash them on the ice surface above the where I was recording.  It was so cold and I had been out on the river for such a long time by this point that I was having trouble fidgeting with record levels on the gear because my fingers were starting numb up a bit.  This did not really work out as I had hoped as the sounds are not that interesting, but something that is kind of cool is simply the sounds of my footsteps walking around above the mic.  They could be useful someday.  Here is a clip of a bunch of impacts followed by footsteps at the end.


Ice Impacts Recorded from Below Surface by azimuthaudio