Me, too - I’ll buy that shirt!
Speaking of Helmholtz resonators (something that I had never heard of before but they make a lot of sense), I can mention the way that Acura deals with engine/exhaust droning.
My Acura RDX 4-cylinder Turbo is noted for having a pretty loud exhaust drone at around 60mph. That, of course, will nevah do for a snooty Acura driver who expects a whisper-quiet cabin, so what’cha gonna do?
This is what Honda did, and I am not making this up:
Since the cabin was whisper quiet to begin with, they turned the whole cabin into the equivalent of a Bose Noise Cancelling Headphone with an “Active Noise Canceling” system. There are something like seven different microphones all over the car from the engine compartment to the exhaust, all sampling noise in their respective areas. Then, no fewer than three on-board computers sample all that noise and quickly figure out what they need to produce for sound waves to cancel out the “unwanted” noise from the car.
Then, they inject that noise-canceling sound wave into the car’s wicked expensive, 1,100 watt, 16 speaker car theater system and, “Presto”! The outside noise goes away. It is amazingly effective and cannot be altered or turned off. That’s the good news.
The bad news is that it uses the car’s sound system to dynamically cancel out unwanted sounds. That takes a whole lot of sub-woofer poop to make those cancelling sound waves and THAT steals power from producing music Bass through the sub-woofer. What you end up with is mediocre music bass/mid response ALL THE TIME.
The cure for mediocre bass response in these cars (according to the Acura owner forums) is to pull a power/audio plug on one specific computer that sits under the center console. I did that and Bass response greatly improved, immediately.
Think of it as an electronic Helmholtz chamber. It is SO effective, that they use those microphones in the engine compartment and at the exhaust to sample the noise, and then inject some of the engine noise back in to the cabin through the infotainment system!
Pulling the plug on that little computer makes half of the engine noise magically go away so it becomes a soft and thoroughly enjoyable engine purr as it shifts through the gears, AND the music Bass response gets a lot better.
Think of it as a gift from our Sainted Japanese Engineers. They must have learned this stuff from Sainted German Engineers. 🙄