As Quiet as it Sounds: Joby S4 eVTOL achieves significant reduction in noise pollution

We’ll discuss in their pursuit to dramatically reduce noise pollution, how Joby’s Actions Speak Quieter than Words:

Joby Aviation (NYSE: JOBY) has been making strides in flight testing, and has been documenting it on social media.

As explained by Austin Thai, Acoustics Senior Engineer at Joby Aviation, Joby envisioned their all-electric eVTOL to generate minimal noise through careful engineering of components like propellers. To evaluate real-world sound impact, Joby partnered with Blue Ridge Research and modeled how its eVTOL aircraft would sound in the noisy environment of Los Angeles. The study compared noise levels of eVTOLs and traditional helicopters on a simulated route between downtown LA and John Wayne Airport.

“To put our aircraft to the test, we went beyond the lab and into the soundscape of a real city. Partnering with researchers from Blue Ridge Research and Consulting, Joby engineers modeled how our eVTOL (electric vertical take off and landing) aircraft would sound against the everyday backdrop of Los Angeles, sirens, traffic, construction, and all.” – Austin Thai, Acoustics Senior Engineer at Joby Aviation

Blue Ridge Research and Consulting

• Based in Asheville, North Carolina
• An acoustical engineering company that specializes in addressing significant noise and vibration issues for clients in the Department of Defense, aerospace, aviation, and industrial sectors.
• Collaborated with major eVTOL manufacturers, including Joby on various acoustical analyses

Sound Design

The Joby S4 aircraft can use its ailerons, ruddervators, and adjustable propellers for trim control, with each propeller capable of changing its tilt, blade pitch, and rotation speed. Multiple trim solutions exist, each with different noise characteristics. Optimal flight control for minimizing noise may vary by location, suggesting that an acoustics-focused approach could improve community acceptance.

Tranquility in the Park

John Anson Ford Park, located in Bell Gardens, California was identified by Joby and BRRC as a location potentially sensitive to noise:

“Ground area, in square kilometers, corresponding to aircraft maximum A-weighted sound pressure level relative to daytime ambient equivalent continuous sound level during the flyover portions of the round-trip flight.“¹

The research findings demonstrated that the helicopter amasses up an area of up to 100 km² above the ambient noise level, with up to 14 dB(A) difference over the Joby S4. The Joby S4 on the other hand, has noise levels below ambient noise. While the authors of the publication note that this is “not an indicator for detectability, but rather a simple comparison of the aircraft level to the average ambient sound level during the day”, in practicality, the S4’s noise signature should be virtually unnoticeable from the ground.

Of great significance, is that the noise levels of the Joby aircraft are less than the ambient sound levels for over nearly the entire area (less than 0.01 km2). The helicopter, on the other hand, emits levels significantly greater the ambient noise, with up to 14 dB(A) difference.

“The study suggests our electric aircraft could offer a different approach – our aircraft may operate with significantly reduced community noise impact compared to conventional helicopters and with zero operating emissions. When aircraft can operate at or below ambient urban noise levels, it opens possibilities for more integrated transportation networks without the acoustic trade-offs that have historically limited urban air mobility. This means communities could benefit from enhanced mobility options while maintaining the quality of their urban environments.” – Austin Thai, Acoustics Senior Engineer, Joby Aviation

NASA Mobile Acoustics Facility

Between August 30th and September 10th 2021,  NASA brought their Mobile Acoustics Facility with 50 pressure ground-plate microphones placed in a grid array to measure acoustics during a multitude of flights at various speeds and altitudes.

“NASA is proud to continue our relationship with Joby by gathering highly valuable aircraft safety and noise data that will contribute towards an aviation future that includes Advanced Air Mobility (AAM) operations.”…”Data from industry leaders like Joby is critical for NASA’s research activities and future standardization of emerging aircraft configurations. Industry partnerships are imperative for the United States to become a leader in the development of a safe and sustainable AAM ecosystem.” – said Davis Hackenberg, NASA AAM mission integration manager.

“We’re thrilled to show the world just how quiet our aircraft is by working with NASA to take these measurements,” … “With an aircraft this quiet, we have the opportunity to completely rethink how we live and travel today, helping to make flight an everyday reality in and around cities. It’s a game-changer.” – JoeBen Bevirt, Founder and CEO of Joby

“NASA has been a critical catalyst in the transition to electric aviation, and we’re proud to have partnered with them on multiple groundbreaking projects since our first collaboration in 2012.” …“It’s incredibly exciting to be the first eVTOL company to fly as part of the AAM National Campaign, leading the way toward a more sustainable future.”…“From day one, we prioritized building an aircraft that not only has an extremely low noise profile, but blends seamlessly into the natural environment. We have always believed that a minimal acoustic footprint is key to making aviation a convenient part of everyday movement without compromising quality of life, and we’re excited to fly with NASA, our long-time partners in electric flight, to demonstrate the acoustic profile of our aircraft.” – JoeBen Bevirt, founder and CEO at Joby.

From day one, the Joby aircraft was designed with acoustics in mind, with the number of propellers and blades, blade shape and radius, tip speeds, and disk loading of the aircraft all selected to minimize its acoustics footprint and improve the character of the sound produced. Each of the six propellers can also individually adjust its tilt, rotational speed, and blade pitch to avoid blade-vortex interactions that contribute to the acoustic footprint of traditional helicopters. – May 10, 2022 Joby Press Release

”eVTOL no buzz?”

Oliver Walker-Jones, Joby’s Head of Marketing, Communications & Brand, made a very witty reply on social media platform X after we commented on the significance of Joby’s accomplishment in reducing in noise pollution:

As Quiet as it Sounds

Does the Joby S4 sound Too Good To Be True, or is it as Quiet as it Sounds? You can listen for yourself!
Joby has demonstrated the difference in noise between its S4 eVTOL, and other common aircraft that can be heard overhead in our everyday environment:

Additionally, you can experience the sounds of a Joby S4 in real-world environments on the Joby Sounds app (available for download on the Apple App Store): click here

Joby Aviation has strived to make its S4 as ultra-quiet as possible, and responsibly share the space in our surroundings without contributing to the noise pollution that unfortunately has been an inevitable reality in the hustle and bustle of modern life. By working with their fellow acoustic experts at NASA and Blue Ridge Research and Consulting, Joby Aviation has shown that they are deeply committed not only to a reduction of hydrocarbon emissions pollution in our environment, but to reducing noise pollution as well. In this unique engineering feat, Joby’s Actions Speak Quieter than Words.

✈️ Stay tuned to eVTOL buzz for test flight updates, tech deep dives, and exclusive interviews as this story evolves

More Info:

From city parks to busy streets: How Joby’s electric air taxi blends into urban soundscapes: click here

Identification and Computation of Individual Propeller Acoustics of the Joby Aviation Aircraft: click here

Contextualizing the Acoustics of Joby Aviation Aircraft Operations with an Ambient Noise Model: click here

Joby Sounds app (available on the Apple App Store): click here

Joby Confirms Revolutionary Low Noise Footprint Following NASA Testing: click here

NASA’s Mobile Acoustics Facility (NASA Langley Research Center): click here

Joby’s aircraft at Joby’s Electric Flight Base: click here

NASA’s Vertical Lift Technology project’s Mobile Acoustics Facility: click here

Joby and NASA Collaborate to Measure Noise Footprint of Electric Air Taxi: click here

Blue Ridge Research & Consulting (official website): click here

1. Thai, A. D., Bain, J. J., Josephson, D., Naru, R., Lympany, S., & Page, J. (2025, July 16). Contextualizing the acoustics of Joby Aviation Aircraft operations with an ambient noise model. https://doi.org/10.2514/6.2025-3138 ↩︎