Apple basically broke the rules of physics to make ANC work with open-ear buds.
Apple’s engineers have done what many thought was impossible: active noise cancellation (ANC) in open-ear earbuds.
But, it’s not as easy as just tweaking the firmware for the new AirPods 4. The solution involved advanced computational audio powered by the H2 chip and data gathered from years of MRI scans of ear shapes.
Why Adding ANC to AirPods 4 Was Difficult Without Ear Tips
Traditionally, ANC has only been seen on over-ear headphones and earbuds with silicone tips. These designs create a physical seal in the ear canal, keeping the external noise out and providing an ideal environment for ANC to work its magic.
So, when Apple set out to bring ANC to their signature open-ear design, they faced an uphill battle.
Without a seal, outside noise can easily get in. This makes it hard for ANC to tell the difference between wanted and unwanted sounds. So, Apple basically had to rethink how to block outside noise while keeping the earbuds comfortable and functional in their open-ear style.
Plus, implementing an effective transparency mode for open-ear designs proved to be even harder.
The challenge lies in seamlessly blending ambient sounds captured by the microphones with those naturally heard through the open design. It’s a delicate balance that’s required to create a natural and immersive listening experience.
Apple’s Solution: Advanced Computational Audio and H2 Chip
To overcome this problem, Apple leaned hard into their expertise in computational audio and chip design.
First, the AirPods 4 use the new H2 chip, which enables real-time monitoring and adjustments to the ANC algorithm up to 200 times per second. Meaning, it constantly adjusts the noise-canceling as the earbuds move around in the ear.
Treski explains that this dynamic process ensures both ANC and audio quality remain top-notch throughout use.
That’s because the chip doesn’t just make constant changes in the noise cancellation levels. It also adjusts the equalizer accordingly to maintain the sound quality no matter the user’s movements and environment.
But the H2 chip isn’t working alone. The AirPods 4 also use a system of advanced microphones both inside and outside the earbud.
A microphone next to the speaker always listens to the sound in the ear, while outside microphones track ambient noise.
This setup, combined with the H2 chip’s processing prowess, allows the AirPods 4 to continuously monitor and cancel out environmental noise – all without relying on ear tips.
How MRI Scans and Pandemic Challenges Led to the Breakthrough
The journey to create ANC-capable open-ear AirPods began years ago (as in EarPods era) with Apple’s early research into ear physiology.
Kate Bergeron, Apple’s Vice President of Hardware Engineering, revealed that they first used MRI scans to look at ear shapes and get data on fit.
These scans helped them create a huge database of ear structures. These helped fine-tune the earbuds’ shape and positioning, allowing Apple to adjust the internal driver and sound direction for better ANC performance.
The real breakthrough for ANC in open-ear design, however, came during the COVID-19 pandemic.
In 2021, a small team of Apple’s acoustic engineers took on the challenge of incorporating ANC into a non-occluding form factor. They developed a prototype that, while not perfect, showed tremendous promise.
“We were just blown away,” Bergeron recalled.
“We said ‘we absolutely have something here, we need to go after this and we’ve got to make it happen.'”
This eureka moment spurred the team to double down on their efforts. They started improving the ANC algorithm, finding the best places for microphones, and fine-tuning the acoustic architecture.
The development process also led to big design changes.
The AirPods 4 now have a new “snorkel” shape at the front, with speakers angled down the ear canal and slightly pushed back. These changes were key in stopping sound from bouncing back to the internal microphone, making the ANC system work better.
Yet, the redesign didn’t stop at the earbuds.
Apple also made a slimmer charging case while making it easier to use. They removed the old button and added a motion sensor that lets users pair their AirPods by tapping the case twice. This change made the design simpler and improved water resistance, giving the case an IP54 rating.