Rocket sound

I've put together a very basic sound engine for my Lunar-lander-on-a-disc game, although it isn't in a released version of the game yet.

It's my first time using XAudio2; it went fairly painlessly. The only trouble I had was with my synchronization between the playback thread and the sound generation thread. Originally I was using an event but it was possible for the consumer to occasionally generate two events (meaning it had consumed two buffers) while the producer was busy. After this happened a couple of times (I am currently triple-buffering) the producer and consumer would wind up writing to and reading from the same buffer, with nasty-sounding results. I switched to a semaphore which keeps a count of how many unqueued buffers there are and it works fine now.

At the moment my sound engine is very, very low-level. I generate sound in small batches (17 ms at a time, one video frame's worth) and feed it to XAudio2 for playback. I'm not using any pre-recorded audio yet and I'm not really doing much signal processing yet either. Since I'm triple-buffering there are a couple frames of latency; I may shrink the buffer size to reduce that.

Now I'm trying to come up with a good, interesting rocket engine sound. All I have so far is some white noise that has been filtered with a 64-tap low-pass FIR filter. It's also shaped with a basic envelope for when the thruster is on or off.

I am currently generating the white noise at 44.1 KHz and filtering it down which is incredibly wasteful. I'm going to switch to synthesizing the noise at 11 KHz or lower and upsampling to the final rate since I am knocking out all the high frequencies anyway. I want to experiment with a dynamically-changing filter as well so I can get interesting transient effects at the start and finish of a rocket firing. I'd like to give the noise more of a 1/f or 1/f-squared shape as well since I think it might sound better (louder bass, softer treble). It's just kind of a generic hiss right now.

I've experimented in Audacity with phasing and it produces some really nice whooshy effects so I may try to come up with a way of relating phasing to what is going on; maybe do phasing based on the nozzle angle or something, so that as the nozzle sweeps back and forth you get some stereo effects.

The steering jets will get their own sound generators as well, and then it's on to impacts, weapons, and whatever else is needed.