How would you design the sound of a submersible propeller?

Question

POST-MORTEM: Using a variety of tools and manipulating them underwater while recording with a 3 different pairs of hydrophones (for a total of 6 different perspectives) yielded truly wonderful results! Thanks to all for your contributions to the thread.

UPDATE: The recording session is coming up! Let's hear some more thoughts, people --

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I have some methods in mind but thought I'd ask the hive mind for some insights. Think:

• Large submarine propellers / screws;
• Smaller scale submersible vehicle;
• Remote controlled ROVs;

Whether you want to achieve a "Hollywood"-style sound (ie. muffled / boomy / echoey) or a more realistic vibe (ie. hydrophonic recordings), let's hear what you got!

Answer 1

That cinematic soft "fwup-fwup-fwup" of a large sub prop element might nice with a low speed fabric-blade fan against upholstery. A small compressor with a long tube might be good for sustained bubble generation.

Warbling, sub-audio-rate LPF modulation might help make things feel aqueous, and blend elements together.

Actual hydrophones seem far too bright for anything but the smallest ROVs, without water pressure on the pinnae they never seem to emulate the human experience of being underwater.

Immersion blenders would be great for a more aggressive sound, esp slowed down 1-2 octaves.

Answer 2

I'm a big fan of the pitched down pool toys. I did a bunch of that stuff here. They aren't pitched down in the library though.

http://rabbitearsaudio.com/product/hydrophonic/

But @noisejockey is correct, there will be lots of high end stuff you won't want. Some other cool elements to play with:

Scuba gear in pool. I'm sure all of those air releases will be useful. Also one cool side-effect I had was the HVAC system for the house I was recording at produced a crazy low-end vibration under the pool. I ended up recording this amazing low end drone. Low frequency vibrations underwater could be used to provide a sense of movement for that sub. That crazy drone is also in that library.

Answer 3

What about not using a hydrophone, but just a contact mic instead? Since the sound transmission through water is not the frequency response you're seeking, perhaps using the drill or other electric motor on another surface, like metal or wood, would imply the same idea but provide a way to get the density of sound you're hoping for and you get to stay dry in the process.

Then you can layer in a performed water element, whether it's recorded on a hydrophone or condomed mic underwater or mic'd from above the surface and rolled off.

This would probably be my first approach.

Answer 4

There are these pool toy guns that are just long water cannon tubes, but hovering them at different depths in and out of the water and also just blowing the empty air tube into different tubs makes some cool sound.

This isn't for the propeller obviously, but could be a good compliment for that water expulsion

-dave

Answer 5

there are three possible approaches to a problem like this:

• using acoustic sources;
• using electronic sources;
• using electroacoustic sources;

in the case of using acoustic sources, you will need some hydrophones, so that you can properly make underwater recordings

please do the following:

• find a proper water recipient or water container
• put your hydrophone inside the water;
• find the proper method for exciting the water;
• just recording

no matter if you recording acoustic, electronic and electroacoustic, it's always advisable to;

• layer as many sound sources as possible;
• control the envelopes of the sounds;
• etc.

in terms of approaches to generate sounds electronically, you will need to:

• use granular synthesis;
• use physical models;
• use fft transformations;

actually granular synthesis and fft, are more like sound manipulation techniques, so you can apply both granular and fft to:

• the acoustic sources your record themselves;
• you can also layer the sounds you record with the digital domain, with the original ones, allowing for richer textures;

if you decide to also generate sounds electronically, a possible approach may be:

• recording some sounds using physical models;
• grabbing the physical models and adding them to the mix;
• processing the physical models with granular synthesis and adding those to the mix;
• processing the granular and the physical models, with fft and adding separate layers to the mix;

then it's pretty much about:

• controlling those envelopes, and the volumes in the mix, to make sure everything blends perfectly

another thing you can do, is searching for folley in actual recording of music, movies, etc., and sampling those, making a library of catalogue sounds with the stuff you are looking. simply try to reframe sequences of movies and songs and other forms of recordings that may include such kind of sounds, and sample those.

finally to summarize mix:

• the acoustic sources;
• the pure electronic sounds;
• the the electroacoustic sounds recorded out of the acoustic sources;
• the samples sources;

do the following:

• mix the volumes;
• control the adsr;