This project is my attempt to recreate the THX Deep Note in Javascript. It was inspired by Batuhan Bozkurt's work on the same thing, but I was interested in how the Web Audio API could be used to implement the same thing.
The prototype sound I'm basing this implementation on is this video on YouTube. This is closer to the original Deep Note; newer ones seem to be generally shorter in duration and at a slightly higher pitch, and this one is the classic that I remember from Star Wars when I was a kid.
The Deep Note is a collection of overlaid sawtooth waveforms which gradually fade in, vary their frequency and pan slightly, then after a few seconds a crescendo kicks in and the fundamentals follow a distinctive envelope to a final landing note (consisting of stacked, detuned octaves around the fundamental).
The deep note is slightly over 30 seconds in length with some events at the following timestamps:
- 0 seconds / 0 – fade-in starts
- 7.5 seconds / 0.24 – initial fade-in completed
- 9.5 seconds / 0.3 – fundamental frequencies start to move
- 14 seconds / 0.45– main crescendo envelope begins
- 18.5 seconds / 0.6 – final landing note is reached
- 24 seconds / 0.775 – fade-out begins
- 30.5 seconds / 1 – fade-out ends
We start by generating the fundamentals that we want to include in the note. Batuhan uses 30 of these, and it seems like a pretty good number to work with. The initial frequency of each fundamental is chosen randomly from between 175-250Hz, and detuned randomly by ±10 cents to add some depth, then a low-pass filter is applied to knock off any nasty high-frequency patterns we end up with.
The frequency of the fundamentals slowly drifts up and down by a small amount that's proportional to their base frequency – that is, higher base frequencies will vary by a larger amount. Each fundamental simultaneously pans between channels to add width.
The UI is built in React, because I have the ultimate goal of allowing the various parameters to be tweaked.
The Note class is the base for playing a Deep Note. We create a Note then call start() on it to begin playback. The Note includes a final gain stage that we use for the main volume envelope (independent of the fundamentals).
## TODO
Clean up main note class