How the season affects if you hear a sonic boom during rocket ascent

Mark Anderson – anderson.mark.az@gmail.com

X: @AerospaceMark
Brigham Young University, Provo, UT, 84602, United States

Additional Authors
Kent L. Gee
X: @KentLGee
Brigham Young University

Lucas K. Hall
California State University Bakersfield

Institutional Social Media
Brigham Young University
X: @BYU
Instagram: @brighamyounguniversity

Department of Physics and Astronomy
X: @BYU_PhysAstro

Popular version of 2aNSb9 – Modeling seasonal variation in rocket ascent sonic booms
Presented at the 189th ASA Meeting
Read the abstract at https://eppro02.ativ.me//web/index.php?page=IntHtml&project=ASAASJ25&id=3989257

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Residents in Southern California have reported hearing sudden, explosion-like sounds that have been startling individuals and causing vibrations in buildings. It turns out, these sounds are actually the sonic booms from rockets launched 70 or more miles away. And whether you’ll hear one is often determined by the season.

These sonic booms are produced during the rocket’s ascent toward orbit (see Fig. 1). As the vehicle pitches over during flight, it produces a sonic boom that can hit the ground below. This has happened with every orbital rocket, including the Saturn V and Space Shuttle, all the way to the modern Falcon 9. The difference is that while, historically, these sonic booms have only been audible over the ocean, rockets today are being launched closer to the coast, making these sonic booms audible on land.

A SpaceX Falcon 9 rocket launches to orbit. Photo credit: SpaceX. CC BY-NC 2.0 (https://www.flickr.com/photos/spacex/51027443336/). Annotation by the authors.

As part of a project funded by Vandenberg Space Force Base, researchers at Brigham Young University and California State University Bakersfield have teamed up to measure these rocket ascent sonic booms. Almost immediately, a question arose: why is it that we can measure sonic booms on land for a few months, followed by a period of almost nothing, even if the rocket’s trajectory stays the same? To answer this question, we used NASA’s state-of-the-art sonic boom modeling software, PCBoom. After verifying that we could reproduce our measured results using day-of weather data inputs, we simulated a commonly flown coastal trajectory using five and a half years’ worth of weather balloon data. This trajectory is among the closest currently-flown trajectories to the coast.

The results came back clearly. The seasonal weather causes predictable patterns in where sonic booms are most likely to be heard on land. More specifically, it typically comes down to which direction the upper-level winds (above 10 miles) are blowing, either from the east (summer) or the west (spring/fall). Because these winds change rather predictably throughout the year, we conclude that, for this launch trajectory, sonic booms on land are most likely to be heard in the spring and fall, with somewhat fewer in the winter and very few in the summer. To visualize these trends, Fig. 2 shows representative examples of where the sonic boom will land for each of the four seasons.

Representative sonic boom footprints from each of the four seasons, generated using PCBoom with day-of weather inputs. Actual footprints for a given day are subject to daily weather differences and thus will not exactly match these plots.

With this new understanding of how the seasonal weather affects the sonic boom footprint, we will continue to work with Vandenberg Space Force Base on further rocket ascent sonic boom research. We hope that one day this research will contribute to a world where future rockets can launch regularly while minimizing disruptions to communities and environments.

Here Comes the Boom! Studying the Effects of Rocket Launch Sonic Booms on Neighboring Communities #ASA188

Here Comes the Boom! Studying the Effects of Rocket Launch Sonic Booms on Neighboring Communities #ASA188

Lower-frequency sonic booms from Falcon 9 launches can feel like little earthquakes.

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NEW ORLEANS, May 19, 2025 – Rocket launches are amazing spectacles, but close-up viewers know to bring a set of earplugs or earmuffs to protect their hearing. However, the boom of a launch isn’t reserved for those who sign up to watch it – it can also be heard and felt in surrounding communities.

SpaceX’s Falcon 9 is a rocket used for both human and nonhuman space missions. Since 2010, the rocket has been launched over 400 times, and one of the launch sites for Falcon 9 is the Vandenberg Space Force Base in California.

“Although Ventura County is 60-100 miles from the Vandenberg Space Force Base, sonic booms and other noise from rockets launched over the ocean are sometimes heard on land,” said Brigham Young University physics professor Kent Gee. “As the number of launches with satellite orbits requiring trajectories along the California coastline increases, these booms are being heard more frequently.”

Motivated by noise concerns from residents in Ventura County, a team of researchers from BYU and California State University, Bakersfield collected 132 measurements from sonic booms over an area of 200 square miles during the summer of 2024.

Makayle Kellison, a BYU graduate student, and Gee will present their group’s work Monday, May 19, at 2:20 p.m. CT as part of the joint 188th Meeting of the Acoustical Society of America and 25th International Congress on Acoustics, running May 18-23.

sonic booms

A view of the Falcon 9 rocket launch from a park in Ventura County. Credit: Kent Gee

“Right now, residents may hear a sonic boom up to five times per month, or not at all,” Gee said.

In 2024, the Falcon 9 rocket was launched 46 times out of the Vandenberg base, averaging almost one launch per week. But not every launch makes an audible boom, and not every launch sound is created equal.

“The magnitude of these sonic booms is not uniform across the county and can vary greatly with weather conditions, launch time, vehicle trajectory, and time of year,” Kellison said. “Communities near Edwards Air Force Base, a hub for supersonic aircraft testing, are familiar with occasional sonic booms; however, an aircraft sonic boom differs significantly from a rocket ascent sonic boom.”

Rocket ascent sonic booms are much lower in frequency and can, indoors, sound — and feel — like an earthquake. The boom’s dominant energy is at a frequency of less than 1 hertz, below the range of human hearing, meaning that the booms rattle homes rather than bursting eardrums.

By collecting data on multiple qualities of the Falcon 9 sonic booms, researchers can help discern how different launch-day variables affect a boom’s impact.

“With a better understanding of the underlying rocket sonic boom physics, we hope to inform Base operations and policy makers, allowing for the space launch industry to sustainably grow,” Kellison said.

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2aPAa6 – Boom Buh-Boom! A brief analysis of a Falcon-9 booster landing

J. Taggart Durrant – taggart.durrant@gmail.com
Kent L. Gee – kentgee@byu.edu
Mark C. Anderson – anderson.mark.az@gmail.com
Logan T. Mathews – loganmathews103@gmail.com
Grant W. Hart – grant_hart@byu.edu

Department of Physics and Astronomy
Brigham Young University
N283 ESC
Provo, UT 84602

Popular version of 2aPAa6 – Analysis of sonic booms from Falcon 9 booster landings
Presented Tuesday morning, May 24, 2022
182nd ASA Meeting
Read the article in Proceedings of Meetings on Acoustics

It’s an understatement to say that rockets are loud. The high-speed exhaust rushing out of the nozzles mixes with the surrounding air, creating sound waves that can be heard over great distances. Even several miles away the sound waves can vibrate your whole body as the rocket lifts off and rides its pillar of fire into the cosmos.

If you watch a SpaceX Falcon 9 launch, you may be treated to another impressive experience: watching the rocket’s first-stage booster return to Earth in a “flyback” maneuver and land (see Figure 1). During flyback, the booster falls through the atmosphere at supersonic speeds, with increasing drag from an ever-thickening atmosphere gradually slowing its descent. Seconds before a would-be impact, a single rocket engine fires up again, landing legs deploy, and the rocket lands safely. Depending on your location, not only will you hear the engine firing during the landing, but it may also be preceded by a startling, rapid sequence of loud bangs. No, the rocket hasn’t exploded; this is the Falcon 9’s unique “triple sonic boom” caused by its unique geometry and flight profile while it was still high above you and falling at supersonic speeds.

Falcon-9 launch Falcon-9 booster landing

“Figure 1. Left: Photo of a Falcon 9 launch. Photo from NASA/Joel Kowsky, public domain. Right: Photo of a Falcon 9 booster landing. Photo from SpaceX Photos, public domain.”

Want to hear a Falcon 9 sonic boom created during flyback? Here are some examples on YouTube.

Considering how loud this “triple boom” is, let’s take a look at its pressure waveform in relation to the other launch and landing noise. Figure 2 shows a microphone recording of an entire Falcon 9 launch and landing at Vandenberg Space Force Base over a period of 10 minutes at a distance of 5 miles from the launch and landing pads. Also shown are half-second snippets of the waveform during each of three main phases. The launch noise, indicated in red, is littered with shocks (nearly instantaneous changes in pressure) while the landing noise, indicated in green, contains many shocks of smaller amplitude and lesser steepness. All three phases of noise contain shock-like content, but the sonic boom, indicated in blue, is much larger in amplitude.

Falcon-9 “Figure 2. A Falcon 9 launch recording, around 5 miles away from the launch and landing sites.”

In order to determine the “sound exposure” of ground observers, we can use the Sound Exposure Level (SEL) metric over each section of the recording, as it accounts for both the amplitude and duration of the recording. The launch phase, calculated over 150 seconds, has an SEL of 127 dB (re 400 pPa2 s). However, the sonic boom – less than 1 second long – has an SEL of 124 dB. Although the boom’s duration is shorter than the launch, the amplitude is much greater, resulting in a total SEL similar to that of the entire launch noise. Lastly, the landing noise after the sonic boom (19 seconds) has an SEL of 112 dB.

This brief analysis shows that the landing noise (including the sonic boom) contributes a large amount of noise, similar to that of the launch phase, and needs to be considered when studying the effects of rocket launches on communities and environments.