Since we wrapped production on November 14, I have gotten about halfway through the first editing pass of the audio for Iron Horses Can’t Be Broken. In this phase I’m going through the roughly twelve hours of raw audio, doing a basic clean-up: editing out flubbed lines, removing various background noise. Since we weren’t able to completely sound-proof ourselves from the outside world, we had some challenges, including distant sirens, car horns, or commercial airliners flying overhead; which occasionally interfered and required us to re-record a line or two, and thus those need to be cut out of the episode.
One of the biggest challenges in not being able to completely control the noise from the outside world was the afternoon that an earth mover somewhere in the neighborhood decided to remain in reverse gear for the better part of an afternoon. We attempted to wait it out, but ultimately the distant (but piercing) beeping continued off and on for hours. Rather than lose half a day of production, we continued in the hopes we could remove it later. This required something of a learning curve on my part — while I knew that a notch filter would probably do the trick, finding the correct frequency to filter out was both the key to success, and a far bigger challenge.
A notch filter is so named because on a line graph showing the volume of each frequency, the volume of a specific frequency is “pulled” down to an inaudible level, making a deep “notch” in the line of the graph. It took several hours of playing around with spectrograms to find the specific frequency of the beeping. Since it was at a much different pitch than the voices, filtering out a narrow band of frequency would leave the vocals largely untouched. Once I stumbled upon the correct frequency, applying the filter worked beautifully, completely removing the beeps without audible damage to the performance. In my audio post-production learning curve, it’s my biggest success so far.
I am eager to finish the clean-up so we can begin with sound effects and atmosphere, really putting the final touches on each episode. The performances we got are gorgeous, and I really can’t wait to share the final product with you.