Bug-squashing noise in my studio

I finished watching Fellowship of the Rings with Dolby Atmos and Dolby Vision. A handful of moments used surround sound spectacularly, but one thing stuck out in my mind throughout the movie. Why is there a high pitch whine in my studio? There’s a slow, rhythmic whirring fan noise somewhere that is bugging me. I swear my TV is introducing a buzzing noise to my speakers when Rocket League is running. A tinnitus-type ringing plays on my surround sound monitors whenever I’m on a Discord voice call. None of these were issues in my studio until I set up 7.1.4 Dolby Atmos, which added dozens of cable runs, introduced new hardware to my rack, and tested the limits of how much gear I could fit in this repurposed spare bedroom.

I will go down this list one by one and figure out where the noise originates. If I’m lucky, I’ll find a solution for getting rid of the bugs.

Whirring Fan Noise

Upon closer listening with a field recorder, I noticed some “digital” chirping along with a droning rhythmic white noise. I hear it most loudly on the surround left and surround right.

Please reference this blog post for a diagram of my speaker signal chain.

I have two sources routed to each speaker through a patch bay. The first step is isolating each source to see which one is causing the noise. Ok, that was easy. It's the Denon AVR (Denon X3700H). With the AVR directly connected to the speakers, the noise disappears. With my audio interface summed in the patch bay, the noise starts. The noise dampens when turning the gain knob on the speaker, which means it’s coming from the AVR. The AVR has digital gain for each speaker output. The noise stays the same even when adjusting the digital gain. I’ve concluded it’s the noise floor of the Denon X3700H, and it may not be fixable without re-thinking how to power and ground my studio. The solution I’ve come up with for the time being is to turn off the AVR when not using my studio to reference consumer Atmos content.

HDMI Buzzing

I have a hunch I will need to spend money to solve this issue. I believe there is a grounding mismatch between my GPU, TV, and AVR via HDMI. The buzzing gets louder with more GPU-intensive tasks. The grinding and buzzing soften when hitting the pause menu, which points me in the direction that it’s tied to GPU utilization. I’ve found little information online about this sort of issue and none which match my current hardware setup. Changing HDMI cables, surge protectors, and different outlets had no effect. I’ve heard awesome things about the product “EBTECH’s Hum X” from colleagues. Supposedly it solves headaches when removing background humming, interference, ground loops, and other power supply noise. I wonder if I should buy 2. One for my PC and one for the AVR… I will write a new blog post when the product arrives.

Discord Tinnitus

I’m not looking forward to diagnosing this problem since it’s such a specific application. I join a Discord voice channel, and I hear….nothing. I turn off my microphone chain and turn it back on. Leave the discord call and rejoin. Nothing. There is no tinnitus ringing in my speakers. Ah. The “Whirring Fan Noise” solution was turning off the Denon Receiver. Could it be interference again? When I power on the Denon AVR, the high pitch ringing returns. I’m not sure which component from my PC would be the culprit for adding noise to a voice call. All three of these issues are starting to look like they’re related.

Conclusions

These noise issues seem related to how the Denon X3700H connects to my studio system. I can only think of a few solutions. One is to replace audio cables and power cables with higher-quality ones systematically. When you have more than a thousand feet of wire in a room, that can get expensive quickly. The power to this studio is on a separate breaker to the rest of the house and has brand new wiring and outlets, which leads me to believe it’s not a house-wide issue. It’s a me-issue.

It seems like the cheapest and most straightforward solution is to purchase two “Ebtech Hum X”s with the hopes that they isolate the PC and the AVR from each other.

What would I do without Amazon? They will get here in 2 days, and I will update.