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Discussion Starter · #1 · (Edited)
Just wanted to share a short video I whipped up to test out a new digital audio recorder using three different mics located in the cabin, engine bay, and clipped on the license plate frame. Being that this test run was to dial in the various mic gain levels, there are lots of repetitive throttle actions to generate different sounds. The phone camera mounted on a DJI Osmo gimbal was pretty much 'set it and forget it' since video wasn't the focus of this exercise. The gimbal was doing its own thing behind my head. o_O

The audio is best experienced with headphones as certain lower frequencies won't come through on mobile devices. As a forewarning, the beginning of the video up to about 5:40 is slow paced and can have some variations in sound level as the gains are being dialed in while trying to drive. After 5:40 or so, the levels are more consistent with the audio blend I prefer when watching YouTube videos which highlights mostly the turbos and BOV sounds with a touch of exhaust and cabin noises to fill things out. The modifications that contributed to the sound profile of the car is in my signature below.

Doing this was a fun exercise and, since audio is highly subjective, it also got me curious as to what everyone else prefers. When watching automotive content, what hits the right spots with captured audio?


 
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Cool setup, looks to run strong! I love how you can quiet it down when you want too!

As far as the audio It is a great idea to mic different points of the car. If you want more focused audio look into a cardioid or super cardioid setup and manual gain is a must. I imagine you used omni lav's near the poi's. Lock that gimbal and get a camera that has a mf. Include some flybys and you are well on your way to better production quality then 90% of the vids on YouTube. If you have Q's feel free to pm me. I have a little experience in tv production 馃槈.
 

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Discussion Starter · #3 ·
Thanks for the feedback! While I don't know exactly what questions to ask quite yet, I'm sure there will be some.

Here are some things that have come up thus far from your reply alone.

The wide range of sound levels the car is capable of producing makes it challenging to tune the gains so that audio recorded from each POI is significant enough to come through in normal driving but doesn't clip during pulls. Using a 6-channel recorder has made it both easier and more difficult in certain ways but allows for much better tuning flexibility of each input gain.

I am not sure whether under-gaining then adjusting later in post is the proper workflow or whether it is better to reduce post work by adjusting the gains as close to clipping as possible so it sounds close to ideal without much post processing. I can hypothesize that doing the latter introduces risk of clipping the captured audio in certain situations. My Photoshop RAW experience tells me under-gaining it would be ideal if the same concept of preserving details that can be brought out in digital post processing applies. What would the pros do?

Being that I wasn't exactly sure what was needed, the mics used for the different POIs were omni lavs that I purchased off Amazon based on widest range of frequency response. As with anything else audio, the published numbers alone aren't indicative of other factors and the sound quality varies for each model even though the numbers are very similar.

I ran a standard TRS cable to the engine bay mic and used a wireless setup for the exhaust since that was more convenient and got decent sound for an initial experiment. My next test is to integrate a 3D/ASMR binaural mic in the cabin and blend that in for more depth since I felt the onboard X/Y 120 degree mic capsule didn't provide enough of that. The POI mics are sufficient but by themselves, are very one dimensional if that makes any sense. Would the cardioid mics be even more focused and flat sounding or, if configured correctly, provide additional depth?

Would running two mics at each POI, whether it be omni lavs or cardioids, one on each bank of the engine bay recorded in stereo help provide better imaging?
 
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Wish the induction sound was more prevalent in the cabin on our cars like the older RB's and 2J's
 

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sounds great LL!

love the BOV's, a mechanical cacophony!
 
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So what we do do for compartmentalized audio channels is isolate the subject you want to hear. Sounds simple-- no pun intended but it can be tricky. Cardioid mics work like the name suggests the sound capture field looks like a heart with the pointed tip pointed away from the mic end. You can talk right next to a shotgun mic (super cardioid) and it wont pick your voice up but will pick up anything its directly pointing at. That is how Isolation is used with mics.

As far as gain, try to keep it as close to 0db as possible at peak. What auto gain does is compress the gain before it clips and boosts it when its quiet. lets take a recorded gunshot as an example. Auto gain will make it sound like a sharp crack but manual gain if used correctly will add substantial depth and even extend that duration of the sound event.

The equipment you have should be ok, the main thing that will affect the final product is adjusting your levels to the correct range (without clipping) 0db and making sure that your interface has the ability for channels to be manually adjusted.

I'm a better operator then teacher so lmk if this makes sense.
 

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Discussion Starter · #7 ·
@livinlrg05 Your explanation made perfect sense and the cardioid capture field was described in a way that was easy to visualize how they work. I should have some time to do additional tests next weekend and will post some more test content. I picked up the Hooke Verse 3D mic yesterday and am anxious to see how that works in the car. Based on the tests around the house, I am curious/skeptical if it'll improve the cabin imaging but will be fun nonetheless.
 
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Discussion Starter · #9 ·
Can't believe it's been three months since I posted the last video. With summer travel out of the way, I finally circled back around to getting something better (GoPro Hero 10) for video and tested out a slightly different configuration for audio capture. For this test, I am still using the lapels for engine bay and exhaust with two now under the hood. The two under the hood added some noticeable depth through the headphones. The driver side channel doesn't seem to be picking up as much detail as the passenger side. Maybe I need to use the same brand of mics for both sides next time.

Also started using the binaural microphones in the cabin which adds some more depth. The cabin mic is really a fine balance between too much and too little because it will push things over top causing the audio to clip if gained too high. Too little and it doesn't make enough of an impact. I think it's the lower frequencies causing the clipping so maybe I need to start learning how to use the crossover feature in Premiere Pro to filter or level out the frequencies causing those thumps.

After figuring out that I didn't want to deal with a clunky DSLR for POV video recording, the GoPro really is the best option. Night driving makes it challenging in my parts of town where people don't like artificial light. This video was recorded in 4k/30 and I'll need to do a higher FPS video next to see if the footage is usable without too much post editing. Not sure I want to do a daytime video yet until I figure out a more discrete way of mounting the camera. Having a GoPro mounted six inches in front of my nose isn't weird at all to other drivers.

Any feedback welcome...

 
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