In May I returned to the junkyard behind the city gravel pit and made some more recordings. The huge petrol tanks I spoke of in my
previous post weren't nearly as overgrown and I was able to investigate them further.
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| The petrol tanks, from the side. |
In one end of the larger tank, I discovered a perforation that allowed me to slip the Zoom H1 digital recorder inside. The end of the tank being essentially a ten-foot sheet of metal, simply rapping on it with my knuckle was enough to set off an immense reverberation within. The microphones were able to capture the sound far more readily through the perforation. It also had the effect of filtering out some of the constant noise from the MDF plant. The plentiful birdsong, on the other hand, was accentuated.
Tech notes: upon reviewing my recordings, there was an exceptional amount of low frequency rumble from this tank. It was easily scrubbed by applying a High-Pass Filter at 129Hz. I kept some alternate takes with the HPF set at 96Hz, which sound much bigger but not as clean. A lot of the MDF plant's shenanigans is in that very low band.
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| The larger tank, you can just see the perforation in the shadow to the left. |
By climbing on top of the 'smaller' tank I discovered an open hatch. The cover of this was still attached, and could be prised up slightly in order to clash against the lip and create more interesting reverberations. I was able to lower the Zoom right into the tank in this case. I did this free-hand at first, but quickly attached a strap in case of droppage. I wouldn't have been able to retrieve it if I'd let go!
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| The hatch. Apologies for the cropping - I was using my telephoto lens. |
In the bottom of the tank is about a foot of liquid - I hesitate to call it water - organic matter that's fallen in, decayed and mixed with rainwater and whatever chemical residues remain from its petrol-holding days. Regardless, it was perfect for dropping small pebbles into and recording the results. I even recorded a couple of 'aaahs' into the bargain.
Tech notes: these recordings required some subtle noise-reduction as well as the HPF treatment. I found that the pebble drops leaned towards the higher end of the audio spectrum, so weren't negatively affected as much by the HPF as the other sounds.
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| The pipes. Most are metal, but you can see a couple of plastic/polymer ones in the upper left. |
I also revisited the large pipes I recorded last time around. This time I placed the recorder inside and clapped my hands into them. It creates a much louder percussion and echo than my metal striker. I had better results if my hands were also inside the pipe.
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| The pipes are approx 18" in diameter, with walls an inch thick. |
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Tech notes: I recorded claps from both ends of the pipe: the one with the Zoom inside, and from the opposite. Those from the opposite end turned out more interesting. The plastic pipe had a richer sound, while the metal one had a more complex echo. Just the sound of my voice, annotating my recordings, came out sounding all 'muzzy' from the peculiar acoustic properties of the pipe interior. Some of it was low-frequency rumble, but I can't be sure how much was to do with the Zoom sitting in the pipe without something to dampen the vibration. These recordings all clipped, despite turning down the recording level, but a little cheating in post-production did wonders.
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| The view down one of the plastic pipes. Overexposed to show the interior walls. |
A fun day out if ever there was one. No doubt you'll be hearing these sounds in future productions!
