Active Noise Cancellation and Audio

I've joined to start sharing my findings and opinions after two months of ownership. I've got some details about the vehicle that I don't think are common knowledge and may be interesting.

First up is Active Noise Cancellation. ANC is a frustrating technology that some manufacturers use to avoid making their vehicles more quiet by adding mass loading dampening material to metal and using better materials. While I will say that Honda has come a long way with cabin noise and the cabin rides quiet at low speeds, there is still plenty of evidence of cheap materials and poor design choices that I have found as I removed door panels, unplugged the ANC module, etc. At high speeds like 75 on highway it is obvious they could do better. They could do worse too, so there is that.

Now, what does ANC do? It tries to put sound waves in the audio system to counter noise of various types, mostly low frequency due to the ridiculous VCM technology that Honda will not abandon, and maybe some mid frequency cabin noise is slightly reduced. VCM is an engine "feature" that shuts off 3 of 6 cylinders when not accelerating and saves a very miniscule amount of gas. Prior versions of it caused oil use and engine wear and it is claimed to be better now- overall it is a useless technology that is not worth the imperceptible fuel savings for the noise, response loss/hesitation, and maintenance issues it presents. It is noisy at mostly low frequency, and so ANC cancels that drone out fairly well using your speakers and factory subwoofer. Neither of these technologies is optional, but with some work you can disable both ANC and VCM without doing anything irreversible. I have no idea what the dealer says about warranty but they do have to prove your changes cause an issue if you had one.

Perhaps the most interesting things about ANC are:

1) if you want to add aftermarket stereo equipment there will be loud feedback in the factory equipment as the ANC mics think your new equipment is making cabin noise. A simple software option to disable ANC would alleviate this, but no Honda could never be that smart (they have the setting but it doesn't work or stay in memory), so you have to phsyically disable the two ANC mics in the ceiling being careful to leave the hands free/phone call mic alone, or you must unplug ANC module behind the glove box. A really sophisticated installer might tap the harness and install a relay switch but that is extreme and expensive modification.
2) Honda is putting FAKE EXHAUST SOUNDS into cabin via the speakers. Yes that is correct. I am about 95% sure of it. I plugged/unplugged ANC and did nearly a dozen controlled speed test drives up and down the same road at night with no traffic for repeatability and there is a distinct undertone or closeness of the exhaust sound in the cabin when ANC module is on. It makes the exhaust sound a bit better tonally but louder in cabin, and overall sounds slightly 'tougher' by boosting the lower tones slightly.
3) ANC muddies your stereo a bit. With it disabled it gets more power and is slightly more crisp because there are not sound waves of opposing frequencies- all power from the audio amp is for your music. The amount of cabin noise it reduces in this car seems to be very small, and I have added sound deadening to the doors and floors in places, so the little bit of additional cabin noise is offset by that and the reduced exhaust sound.