Getting Good Audio on your Se7en for a Track Day Video

This article is the collected wisdom, or rather, lack of (my) wisdom in a long running thread on getting decent audio on an action camera track day video in my Caterham.  While I was trying to get engine/exhaust noise instead of wind noise on a track, the lessons will still work on your back road blats with an action camera bolted to the roll bar.  

Lots of people have asked me over the years on how to reduce wind noise in there driving videos - road or track.  While I am not an expert, I have done a lot of experiments over the years to form a view of what works and what does not.  Your own experience may differ and thats good because you can also contribute that on this USA7s forum.  

I am not going to cover which is the best camera or mounting systems in this article – just want to focus on sound. I personally want a good throaty engine/exhaust sound in my videos, nothing annoys me more than seeing a great video with some crap music overlaid. I want to hear that engine roar at revs. If you are like that read on. If you prefer crap music then stop reading now.

Its easy to get decent sound up to about 40mph.  Its after that, you begin to hear increasing wind noise.  

I am not an audio engineer – I just know what I like listening to in a sevens driving video.   I am trying for high quality sound – some of you may agree with me and others may want to short cut.   All of us are right – we deserve to get what we want.

A Se7en has unique acoustical properties:

- They are aerodynamically dirty so lots of wind noise is a given.

- They have a light construction so they transmit more vibration, noise and even electrical interference.

- The light construction can sound “tinny” instead of resonating a nice deep note that a regular car might do with its more enclosed and insulated spaces.

- They have lots and lots of wind noise….did I say that already?

So this is a challenge that even open-wheel race cars don’t really have as most of them have slippery aero bodywork that can hide microphones from the wind, unlike a seven.

Many of the video examples below are illustrating how the sound changes with the different methods. Don’t listen to the whole thing – listen just enough to get a sense of what works or does not work.

So let’s start at a baseline. The GoPro or any numbers of action cameras advertise fantastic sound quality out of the box. That might be so when you are surfing, horse riding, riding a mountain bike, rock climbing or running around with your girlfriend in a meadow.  However that is not true when you stick an action camera on a Se7en and ask it to record a spirited drive or track event.

For example here is an action camera using its internal mic in its regular case perfectly mangling the glorious tones of a beautiful Cosworth Duratec engine in this gorgeous Caterham:

Hmmm…. So that does not work. 

Lesson 1 – Position the microphone out of the wind.

So let’s try and use an external microphone and see if that improves matters? Just a simple Olympus ME-52W connected to a POV VIO HD camera with the mic under the canvas tonneau in the boot area:

Not great.  One of two things is happening, (a) the level of noise is over-powering the ability of the mic to process the sound, and/or (b) the mic is over-powering the ability of the camera to process and record the intense noise frequencies.

So with exactly the same mic mounted in exactly the same position let’s try it with a Go Pro HD2:

That’s better. Still a little soft in volume and too much wind.

Lesson 2 – Some cameras are better than others at processing recorded sound.

Somewhere around this point in my discovery process, I read lots of tech articles about how you need a powered microphone to improve dynamic range, improve gain and improve recorded audio quality.    So I graduated to an Audio Technica AT-3350 lavalier omnidirectional microphone. This has a little battery within it. So let’s mount it to a GoPro and locate the mic under the rear tonneau in the boot area.

Much better. Much more differential noise than I would like.   Still some wind noise.  Not as throaty as the engine sounds in real life – a little thin sounding.   Still not a great recorded representation of the sound we hear from our cars.

Lesson 3 – Power is better than no power when using a microphone

So now I am thinking I need to move the mic around to find a better position within the car. Positions tried and discarded:

• Under the passenger and driver’s seat – too much wind noise
• Under the dash on the center tunnel – too much wind noise. I guess air flow rolls off the dash and circles under the dash and foot well area?
• On the rear wing in front of the exhaust tip – way way way too much wind noise even with a 'dead cat' cover, also known as a 'dead kitten' cover. A 'dead cat' cover is a furry item that covers the entire mic recording element and is intended to protect the mic from hearing the wind.  Example linked: https://www.amazon.com/dp/B07RKT7LLH/ref=cm_sw_em_r_mt_dp_98M5VD26QPTMR1QR2M5Q
• Mount the lavalier mic to the exhaust tip using painters tape.   Don't repeat my mistake - I burned the tape, melted the mic, recorded nothing worthwhile and I felt like a right muppet.

After hanging upside down in my passenger footwell, I saw a nice ledge way way up under the passenger side dash where the relays are located. So I gave that a go.

I also upgraded mics to a borrowed demo model of an Audio Technica AT689. This is an expensive powered mic (now superseded). I do not recommend trying this at home.

Much better. No wind noise now but because it is next to electrical components and it is unshielded you get static and interference. You also can hear the cycling of the fuel pump relay if you listen carefully. So that is another fail.

Lesson 4 – Sticking your mic next to electrical components in a car will likely get some static/interference noise

I do learn that a better quality microphone will produce better sound recording results – you get what you pay for. From my phone discussions with the GoPro tech people on how they produce their videos I learn that they frequently use a Sennheiser MKE400 or in one case a Rode Video Mic. Both are priced in the $200 range. They also sheepishly admitted they from time-to-time use separate digital sound recorders to blend sound into the sound recorded by the camera on a post-production basis. More of digital recorders later.

Lesson 5 – With microphones you get what you pay for

So let’s try the same mics and locations in different cars of different USA7s members to see if I can replicate the results consistently.   Using Jeff's @JBH Caterham, I set up a test with an AT-3350 mounted in the boot area under the tonneau using a GoPro HD2:

Without showing you the failed attempts, I eventually succeeded.  Experiment replicated.  

Consistency is a challenge. I installed all of these mics using the same technique I tried on my car and I do get failures at an unacceptable rate. 

Some issues driving the problems are:

• Car vibrations making the mic to camera and internal mic connections break.
• Flat battery in the AT-3350 (no idea how long the battery lasts – I seem to get 1.5 days continuous track time from my testing but it always seems to go flat precisely when I really want to rely on it!
• Forgetting to turn the on switch on the AT3350 (no excuse – shoot me!)
• Vibrations eventually killing the mic so that it no longer records (internal fault to the case or some break in the mic wire?). Been through 3 mics this way.

It is very difficult to work out at a track or during a drive whether you are recording good sound or not. There is no effective way to test this out in the field. Easily done on a laptop though but who wants to do that in the middle of a drive?

Keeping it simple is important as you have a lot to remember to coordinate when you are about to go on track (helmet, gloves, belts, camera, fuel, mic turned on, bonnet clipped down, etc.).  A Sunday blat is easier but you still want to get out and drive rather than faff around with a microphone.

Lesson 6 – This learning process can be frustrating!

So now I try for the Holy Grail. I give up on the cheap but fragile AT3350 and I run the AT689 mic forward to the engine bay and again using 3M painters tape, tape it to the shelf above the passenger foot well. The metal in theory should shield the mic from electrical interference and I should get lovely throaty sound from the roller barrel throttle bodies. Recorded with a GoPro

And so it works. On back off I do get a tinny (another technical term of my making) sound as the intake is closed off but the rest of the sound is perfect. I even hear the CR500 tires being tortured through the corners.

Lesson 7 – Engine bay on the intake side can produce really good sound with an external mic.

So now can I replicate the sound using different mics same location? GoPro HD2 paired with an Audio Technica AT Pro-CM24 shotgun mic.  You are riding aboard with Mike @Kitcat in his Caterham.

Success!!!    The AT Pro CM24 was mounted drivers side above the pedal box on the Caterham.

As a contrast here is an Opteka VM2000 shotgun mic taped to the inner scuttle above drivers knee – not bad but a bit rattly and more wind noise than I would like. Would prefer just engine noise/exhaust noise.

Lesson 8 – Engine bays are a good location for microphones as wind noise is largely minimized and intake sound is pretty good

So now my question is does it work with other cameras?   Yes – tested the AT689 with the Drift HD Ghost and the Braun Six Zero with mic mounted up under the bonnet above the passenger foot well.

Braun Six Zero Camera and an AT 689 mic

Drift HD Ghost and an AT 689 mic

The Drift camera is not quite as good as processing sound as the Go Pro or other cameras with an external microphone. It picks up the deeper intake notes but seems to have trouble with the higher pitch notes once the intake is closed. Seems like Lesson 2 holds true.

Lesson 9 - Some level of testing is required to make sure these solutions work on your seven. There is no out of the box solution for a seven

So then I tried separate digital recorders, both mounted in the cockpit using the screw clamp mount. The first tried was a Tascam DR05 and the second was a Zoom H1. Most professional videos will use a separate recording source rather than use a mic attached to an action camera. This makes sense when you think about it as a digital recorder of sound is a complex piece of equipment, larger than the action cameras we are using. So its dynamic range, sensitivity of mic, noise reduction, and general ability to record a good track is always going to be better than the compromised equipment contained within a tiny GoPro box or the like.

The one major downside with these is you have to spend time post production synchronizing video with sound (either with the regular video editing package or an application like Race Render. When you start recording you would clap to get a visual and aural cues from which to base the synchronization

However, I found the vibrations from the car killed both the Tascam and then the Zoom H1. They would turn themselves off or just not record. So they were returned for refunds.

Lesson 10 – Digital recorders offer the promise of better sound recording but more stuff to fuss with recording and sync with video later. Better to keep it simple

What sounds good to me does not sound good to others.   I prefer a little more bass in my sound mix. Others may prefer a little more treble when they hear their car recorded using my equipment.

Lesson 11 – Sound is a personal thing. You may not like what I like – so experiment.

This is my view on getting decent video sound on a Seven drive or track day. I don’t profess to know all the answers so please constructively contribute with details and examples of what you think works well for mic position/location and equipment used.

Lesson 12 - If you want to go to the next level then listen to some better experts in this field

I have continued my personal interest in this topic by following up with WindCutter who specialize in sound recording solutions including wind shielding for microphones. Below is an extract from an email exchange I had with Michael Stamp of WindCutter. He very kindly consented to me posting extracts of his email on this forum as I believe it is very helpful for us to hear from a professional.  Indented text in blue is from Michael's email:

A link to Rob Nokes Guide to Recording Cars is here:

Rob Nokes Special: Guide to Recording Cars (designingsound.org)

I will note that I use the WindCutter microphone "dead cat" wind shielders and they have been the most durable out of all brands I have used so far, although I suspect they would melt if taped to the exhaust...

Lesson 13 - Keep trying!

Continuing in my journey of quality audio on Caterham track videos, I have reached 'nerdvana'

Garmin VIRB action camera mounted to rollbar using a Manfrotto clamp. Twin mic set up using a 3.5mm cable splitter. Twin AT Pro CM 24 mics - internal battery power works better than camera providing power to mic. Both mics are covered with 'dead kitten' mic covers.

One mic runs forward along passenger side of cockpit and around outside of scuttle into engine bay where I tape down the mic with non-marking painters tape under the intake on the top of the passenger footwell inside engine bay. Photo link shows the line of blue tape and camera on roll bar.

Second mic runs backward and is taped down next to rear exhaust - photo illustrates. The blue painters tape shows the line of wire between camera and mic.

End result is pretty good.

If you have a side exit exhaust then revert to single mic setup with mic in engine bay or second mic inside boot (under boot cover) near side exhaust.

Conclusion 

I hope your efforts end up as satisfying as I am with my end results.   Look forward to seeing you post your backroad blat and track day videos on this forum.