MGL or SW Avionics V6 Transceiver/Intercom settings

VOGAD is an Audio filter.
Are you sure this is not an electrical issue?
It is surprising that the cockpit gets noisier when you close the canopy.
Were you wearing a helmet headset in the open cockpit?
Have you tried a different headset?
When you are suffering from the audio noise, will closing a fist over the microphone make it go away?
Have you tried turning the MIC Gain Waaay down?

Hiya Bill!

Removing or installing the AR-1C canopy is not a trivial task, so I am loath to this for any further comparison tests. I only have about 60 hours AR-1C experience, and 50 of those were open canopy while using the same MicroAvionics headset with a helmet. Now it is cold in Colorado. There is no room for helmet with the canopy installed. With canopy installed, hand over microphone, or reducing power, lowers the noise level. Unplugging the rear headset also lowers the noise.

I think the engine noise dissipates rearward with no canopy, but the noise is funneled into the cockpit when canopy is installed. The "turtle deck" cowling over the engine and connecting to the aft edge of the canopy is removed with the canopy de-installation. I also understand the 915is has more transmission gear noise than its less powerful siblings. But I am quite new to Rotax.

Experimenting with mike gain, volume, and VOGAD settings is where I am at. I hope I can find a friendly and knowledgeable BOAF (bird-of-a-feather) using the 915is and MGL combination, perhaps in a full canopied gyro, who can suggest, "set rear mike gain to x, VOGAD high to y, VOGAD medium to z ..." etc. I may also try adding some sound deadening materials if it can't be mitigated by MGL adjustment.

There is no need to remove the canopy.
Is the noise problem only while in flight?
Is it a problem with the engine at idle?  During runup?
Is it a problem with the canopy Open on the ground?
Are you saying that the canopy is open at the rear to the engine when installed?

If it is still a problem with the mic muted by a closed fist, I doubt you could install enough sound-absorbing material.

I am suggesting that the problem is not the canopy change but the Headset change.

Have you tried a different Headset?  *** <---<<<  ***

Remember that VOGAD is just Voice Operated Gain Adjusting Device; A Fancy VOX system.
It sounds like you have Way too much Mic Gain, Start with it set to minimum and work your way up.

I fly a Calidus Gyro and the cockpit is definitely much quieter with the Canopy closed.

Headset: SoftComm C-60
VOGAD: High 1
Mic Gain: 0.00 dB
Mic Levels: 1
Mic Filter: OFF

Thanks Bill. I will start with your initial  settings  next test flight in a couple days.

I have another noise canceling  headset, but not sure about how to wire it. Can check with Abid. Is your SoftComm active noise canceling?

The problem is most bad when flying at higher cruise power. The canopy is not "open" to the rear. There is a fiberglass separation wall behind the copilot's head, but very thin.