It can now be revealed that a group calling themselves Birdwatchers gathered in the sand dunes of the western Gulf Coast in South Texas to record the launch of the most powerful rocket ever built using Sennheiser mics this summer.
The test flight of SpaceX’s Starship developed twice the thrust of the Saturn V that put NASA astronauts into space. It was captured and mixed by the group in immersive audio using Sennheiser’s AMBEO VR ambisonic microphone.
Jason Achilles Mezilis, a Los Angeles-based rock musician, producer and extraterrestrial audio engineer, said: “These rockets are so loud that they’re tearing the air to shreds, so what we’re trying to capture with these launches is where sound ends.”
Mezilis and his fellow Birdwatchers – a group that includes Benny Burtt, a sound editor at Skywalker Sound, Justin Foley, system engineer at NASA’s Jet Propulsion Laboratory (JPL), and Andrew Keating, audio engineer with Cosmic Perspective, a company documenting space exploration – have been capturing launch audio and 360-degree video for several years.
For this mission, the group positioned a Sennheiser MKH 418-S M-S stereo shotgun microphone and a pair of MKH 8070 long shotgun mics about half a mile south of the launch pad and placed the AMBEO VR mic a mile to the north.
The microphones were recorded to Zoom F6 and F3 recorders at 192 kHz, 32 bit, making the most of the machines’ floating-point capabilities to handle the massive dynamic range. The recording machines and microphones are set prior to launch, and because blast-off may be delayed, they must be able to record for 48 hours.
Mezilis explained: “As long as that rocket’s fuelled and on the stand it’s basically a giant bomb. You can’t go back to check your equipment.”
The dunes and a concrete pillar on the pad shielded the array of shotgun mics from the rocket blast and much of the dust and debris, he added.
The idea to use immersive audio to record the sounds came from Gabe Herman, an engineer and producer, who is also associate professor of music production and technology at The Hartt School, The University of Hartford in Connecticut.
To assist with the goal, Herman introduced Sennheiser to the Birdwatchers, and they welcomed him into their group. Accurately capturing a rocket launch trajectory is a challenge, Herman observes, not least because the flight path curves.
He said: “We had a theory on the last launch that we needed two shotgun microphones that could be very narrow and focused to track the rocket as it ascended from earth.”
As a result, they deployed a pair of Sennheiser MKH 8070 long shotgun mics. “We hoped we could capture the beginning of the launch with one microphone, then the second microphone, angled a little higher in the sky, would catch the second half of that ascent. But those microphones are so good, so narrow, specific and focused, that we didn’t capture the arc the way we hoped. That said, the AMBEO mic was very successful in capturing a very compelling immersive field.”
Mezilis added: “The 418-S gave us the meat of everything. That mid-side mic is incredible. The AMBEO VR filled in much of the space behind and around that mic. Because the AMBEO mic is on the other side of the rocket we had to flip the stereo image.”
Herman continued: “For the next launch, we are curious to learn more about how sound behaves at the launch site, which will likely require specialised equipment. Because the air is literally destroyed, it can be difficult to understand the nature of the awesome force taking place at launch. We hope to build on existing research on this phenomenon and make that more accessible to students.”
Capturing a launch presents a fixed data set for later study; he says. “This last launch was a scorching success in that we learned so much about what to do for the next one. Every new launch allows us to refine the data set and generate more informed questions.”
