Yesterday I came across a sound design challenge I've faced a handful of times. I needed electrical crackling/humming sounds (think Tesla coil). The sequence required both a steady sound as well as some fast whooshing of these sounds by the camera. I have needed these sounds enough times that I decided it was time to try and create them from scratch instead of using some old standbys.

To start, I needed a really great warm humming sound. My first thought was to get up and see what kind of sounds my light bulbs were making. Trying to find this in my lamps proved fruitless because as it turns out, we have gone through a handful of lightbulbs (requiring a number of trips to Home Depot by our Boom Box Post interns) to avoid just such a noise in our editorial rooms. As I headed to our storage room to try and dig up some of the noisier light bulbs we had rejected, I heard a loud noise coming from the kitchen. As luck would have it the compressor for our water cooler was freaking out and making quite a racket. I grabbed my Sony PCM-M10 portable recorder and ran to the kitchen.

I got behind the water cooler and recorded the compressor for about a minute, both untouched and with a little shaking to try and create some movement. I was careful not to shake too hard. The last thing I wanted was to accidentally fix the cooler and lose the interesting sound it was making.

Next I put a wind screen on the recorder and waved my hand up and down across the compressor to get some cool doppler/volume curving on the sound. These would be perfect for the whooshing by camera moments.

Upon initially loading these recordings into Pro Tools, I was struck as to how great they already sounded. This is a testament to capturing great recordings from the jump. There wasn't a ton I needed to do to get these in shape for the edit.

I worked on the steady to try and add some variance and texture. After cleaning up a few random ticks with iZotope RX declicker, the sound was run through a pretty simple effects chain. I played around with the Pro Tools built in Sci-Fi plugin to add some warble (using the broken radio preset). Next in the chain, I added Waves' Doppler plugin to try and get as close to that zapping, volume jumping Tesla coil sound as possible. I automated the tracking time, drawing in variations so the movement didn't get repetitive.  

For the next step, I chopped the file in half and layered each half on top of one another, making the file more random and more active. I panned each layer to create some stereo separation. There's a lot of movement in the Left and Right channels, but that can be easily summed to mono should I need it calmed down in the edit. I made a few versions of the sound at this point with varying amounts of additional pitch and time manipulation, eventually landing on a pretty active version that I figured would cut through nicely in the mix. As always, I was sure to save and label each final variation. You never know when one version which isn't quite right will become the perfect sound for a future edit.

As a last step, I ran the processed sound through Native Instruments' Molekular. I had just bought this plugin and welcomed the excuse to play around with it. The resulting sound took on a new life and ended up giving me a great third variation.

For the camera bys I added a very light wind ripple, again using Waves' Doppler plugin (if you haven't guessed by now, a personal favorite), manipulating the pitch for more variations.

Inspiration can come from all kinds of sources. I was lucky our water cooler decided to go haywire at that moment! Funny enough, I hadn't heard that sound previously nor have I heard it since. I think I have the Boom Box Post studio ghost to thank for the assist on this one. I'm thinking we should name him Gerald but suggestions are welcome.