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moving stereo

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Experimenting with moving or POV stereo ambiences…

March 6, 2021
Setting off in the cause of research…or seeking ridicule?

I think Lockdown III must be getting to me: I’ve been pondering over stereo ambiences for film lately, wondering if they ever are or should be recorded while moving to match the POV (point of view) of the camera?

This was stimulated by thinking about sound for an upcoming project with drone footage, where the drone will follow the course of a small local river from source to sea – flying fairly low and slowly. I want the sound to match the view – along the bubbling stream, the passing over of weirs, cows and sheep being flown past etc. Obviously bunging a couple of mics on the drone isn’t an option given the noise of the motors and rotors, so any ambiences will need to be recorded quite separately. Initially I thought of helium balloons: I calculated that seven normal-sized party balloons would lift a pair of Rode Wireless GO II transmitters into the air, but, the more I have thought about this the more complex it seems: a totally windless day seems essential and, even then, trying to stop the mics spinning or, harder, trying to get the balloons in the right place seem fraught with difficulties. And then, more fundamentally, what does a moving stereo recording actually sound like? In other words, would it even be worthwhile trying to do this?

Recording to the miniscule MixPre-3

Drawing a blank through internet searches (the nearest thing being people trying to record the sounds of – say – a bike travelling, rather than just the ambience without evidence of the mode of transport), and not knowing how the soundtrack of any film with apparent moving stereo ambiences was actually made, it seemed easiest to experiment. A bicycle appeared to be the best bet for near-silent travel, as long as fast speed or free-wheeling was avoided. After initial less than satisfactory attempts with semi-binaural set-ups of lav mics by my ears and either side of a rucksack (both getting far too much bike noise, and, also, showing up the inadequacies of furry wind-protection for these mics), I rigged up a boom pool to a sheet of ply, cut to the shape of a rucksack, to mount the mics well above me (so further from the bike and road noise) and to prevent unwanted rotation. The mics were omni SDCs mounted end-to-end in a single blimp to minimize windnoise (see my post here on using mics in this way). Extending the boom pole very far got unwieldly, so it was only partly extended. Sound was recorded to a Sound Devices MixPre-3 on a light harness. The results were in a different league to the lav mic experiments, but the bike was still very evident and, above all, I’m not at all convinced that the sense of movement is very strong. This last point is critical. In short, I have no doubt that a better result could be achieved by recording general ambiences and specific sound effects from static positions and amalgamating them into the soundtrack to give the illusion of moving through space: doubtless this is what sound designers know and do, anyway, but it is good to experiment and find that, sometimes, the seemingly logical approach doesn’t work. And if, in doing so, I’ve gained an eccentric reputation in the village (yes, cycling with a blimp on a vertical boom pole does look extremely silly), then so be it…

For anyone interested, here is a recording of one of my tests with the SDC spaced pair in blimp, including the reaction of a passing neighbour.