I dropped one of my piezo hydrophones into a pond in Kilmacurragh Botanic Gardens in Wicklow on a beautiful day in early summer and captured some interesting chirps and clicks.
I suppose could be some insect life, but I’m not sure. If anyone has any idea what they might be, I’m all ears!
Below is a short, filtered excerpt from the recordings of the day
A Pond at Kilmacurragh Botanic Gardens
I have been neglecting this page of late, which is something that I wish to remedy. I have been quite busy teaching and taking care of other bits and pieces but I did get a chance to recently visit the University of Bordeaux in order to present some of my work at le SCRIME (Creation and Research Studio in Computer Science and Experimental Music).
This was a great opportunity to work in their Hemicyclia and see their impressive 3D dome, a hemispherical array of speakers. In addition to presenting some older fixed media pieces, I composed a piece especially for the trip entitled Bolides (to be available on this website very soon).
Unfortunately, the 3D dome was under maintenance at the time of my visit so I did not get to take full advantage of the ambisonic potential of the dome coupled with the supercollider-based 3D spatialisation software MOSCA. I did, however, get to diffuse my works in the Hemicyclia which features an impressive array of loudspeakers.
A massive thanks to Thibaud Keller, Gordon Delap, at all at le SCRIME for facilitating the visit, which was made possible with funding from the Irish Research Council as part of the Ulysses award.
https://scrime.u-bordeaux.fr/Agenda/Shane-Byrne-Sortie-de-Residence
Over the past number of months, I’ve been experimenting with various hydrophone designs with varying degrees of success. I don’t really know why I became interested in hydrophones but I guess you don’t know what can be heard if you don’t listen.
I attempted to follow along with Zach Poff’s designs although I had an issue with reassembling the electret microphone capsule once I had drilled a hole in the top of the casing. For the life of me, I just couldn’t get it to work again. I’m sure it’s down to clumsiness on my part but I decided to investigate other means of capturing sounds underwater.
One method was to use a pair of piezo discs on the inside of a tuna can. I fixed the discs in place at the bottom of the can with hot glue and then filled the can with silicone to protect the circuitry and discs from water. I then sealed the can and dipped the entire enclosure in PlastiDip. This worked well but was incredibly bulky. It also got a few knocks when testing it off a local pier resulting in some of the plastic coating tearing and a little water got into the enclosure. It still worked but there was some intermittent noise caused by moisture inside the enclosure.
The next method I attempted was to place an electret microphone into a small bottle filled with oil. The idea was that the vibrations traveling through the water would be transmitted via the oil onto the diaphragm of the electret capsule. The theory was that the capsule would not be damaged by the oil as the oil is not conductive. As it turns out, the oil I used was more like perfumed paraffin so needless to say the electret stopped working soon after being tested. I tried again a couple more times with a different kind of oil before arriving at the design pictured below.
The entire capsule and connections are first dipped in PlastiDip before being placed in a small bottle (I think it originally contained eyewash), although this greatly attenuated the strength of the signal. I also stuck about half a dozen washers to the bottom of the bottle to weigh it down in the water. I was sure that this version would stand the test of time but unfortunately, that wasn’t the case, and after about a month or so this too has stopped working.
I did manage to get some nice recordings before the entire thing stopped though. Below is a short clip of the hydrophone being pushed in and out of a bunch of kelp by the tide.
Finally, I admitted defeat with this particular design (if anyone reading this knows what the issue was please get in touch). I returned to the piezo design but this time I used a smaller disc and set it into a brass plumbing fitting. I encased the disc in copper tape so as to create a balanced connection and then set it in place using epoxy resin, careful not to allow any epoxy to get onto the face of the disc.
Once the epoxy had set, I gave the mic a few coats of PlastiDip and then that was that. The PlastiDip will attenuate the signal a little but it is flexible enough to still work well and the signal to noise ratio is workable.
The mic needs a preamp as piezo discs tend to be quite tinny-sounding when used on their own. I use a little preamp that I put together using this design here. I have yet to have a chance to test it out in the sea but I did get out in a kayak recently. The river was quite shallow but here’s an excerpt of the hydrophone being dragged in the wake of the kayak. Some interesting almost formant-like sounds at times. More experiments to follow.
I’ve been experimenting with using coils to listen in on electromagnetic signals in preparation for an upcoming project. More specifically, I’ve been using a pickup from an old broken electric guitar to listen in on the electromagnetic radiation generated by everyday objects. Things like mobile phones, televisions, motors, really anything that generates any kind of magnetic field. I’ve had some interesting results listening to the quasi-tonal sounds created by the various mechanisms in my car.
I first came across this technique when reading the excellent Nicolas Collins book, Handmade Electronic Music. In it, he also suggests using a telephone coil pickup to listen in on these signals, but they’re pretty rare these days so I haven’t had a chance to compare the two approaches.
After taking several walks through town and listening to various devices around my house, I gathered a large variety of source material and started experimenting with various processes in order to create short rhythmic phrases and evolving textures. Many of the textures I used were created by playing around with the harmonics of the ubiquitous 50Hz mains hum that dominates the electromagnetic landscape in any populated area through the country.
Here’s an extract from one of the outcomes of these processes:
I recently bought and assembled the INSPIRE VLF 3 Kit and have had some success capturing what is sometimes referred to as the natural radio of the Earth’s magnetosphere. (It should be noted that I’m only becoming acquainted with these phenomena, and my understanding of the physics behind VLF emission is patchy at best. Over time I’ll hopefully improve on that!)
These emissions occur within the VLF band (3 -30kHz) and are produced by electromagnetic activity caused by phenomena such as lightning, aurorae, and solar flares within the Earth’s ionosphere.
There are generally three types of VLF signals caused by lightning: sferics, tweeks, and whistlers. The characteristics of each of these sounds are a result of the distance around the earth that the signal has had to travel.
Sferics are perceived as clicking and popping sounds, not too far removed from the sound of a crackling fire. Sferics can travel from thousands of kilometers around the globe, bouncing back from the Earth’s ionosphere to the ground and back again.
Along with the sferics, there are also tweeks on this recording which sound a little like birds chirping. Due to the fact that they have likely traveled from a greater distance than the sferics, there is a displacement across the frequency spectrum due to the higher frequencies traveling slightly faster than low-frequency components (apparently?).
Finally, there are some whistlers in this recording which can be heard at 1:42 and 2:40. Whistlers exhibit a greater frequency dispersion resulting in the characteristic whistling sound.
There is quite a lot of man-made sound on this recording which can be observed on a spectrogram as steady horizontal lines. One such sound that is hard to escape is the ever-present 50Hz hum generated by mains electricity. Although I was probably at least 500m from the nearest power line I still had to remove the hum and associated harmonics from the recording.
There are also some curious signals between 16kHz and 25kHz. I’m not sure what they are exactly but I’m going to do a little more reading to find out.
This recording was made around 23:30, 2/7/21 just above Limekiln Beach in Wicklow.
I’m finally starting this blog having threatened to do so for quite some time. The main purpose of this will be to share and archive my work as it happens along with any other bits and pieces of interest I think I may wish to refer to again in the future.
Seeing as I’ve put this on the long finger for some time, I may share some past work here too, all in the hope that any findings or outcomes don’t get lost to time and broken hard drives.
Who knows, maybe some of these ramblings can be of benefit to someone else’s research in the future?
