In-ear headphones have long been a favorite among users due to their lightweight design and comfort, making them a popular choice for long-term listening.
However, from an engineering perspective, they represent one of the most challenging form factors to implement noise cancellation in. Unlike in-ear headphones, which rely on silicone ear tips to create a physical seal, the open structure of the ear tips makes it much more difficult to precisely control the sound.
With the Enco Air5s, OPPO set out to improve the active noise cancellation (ANC) experience in in-ear headphones by making it stable, natural, and comfortable.
“As OPPO’s first in-ear headphones with active noise cancellation (ANC), we have optimized the Enco Air5s in terms of acoustic architecture, ergonomic design, and intelligent adaptive algorithms. For the user, this means achieving the same critical balance between immersive silence, natural sound, and long-lasting comfort,” said Daryl Zhang, Product Manager of Enco Air5s.
One of the biggest challenges for noise cancellation in earbuds is the lack of a physical seal. Without silicone ear tips to seal off the ear canal, ambient noise can enter through multiple acoustic pathways, making the internal sound field much less predictable. Real-world noise is also complex in nature, spanning a variety of frequency ranges, including human voices, traffic noise, and city sounds, making it much more difficult to achieve effective noise cancellation.
To enhance the stability of ANC in an open acoustic structure, the Enco Air5s feature a specially designed 1,4mm² short-circuit acoustic vent. Simply put, this vent helps control the interaction of external sound and air pressure with the ear canal, providing the noise cancellation system with a more stable acoustic environment to operate in. Rather than simply blocking or letting in noise, this design carefully regulates the pressure difference between inside and outside the ear canal, creating a more controlled and predictable sound field.
After extensive testing and tuning, the 1,4mm² configuration was selected to better balance noise cancellation performance across different frequency ranges, helping the Enco Air5s provide more consistent suppression of low-frequency hum, ambient sounds, and human voice noise. This acoustic architecture is the foundation of the ANC system.
Compared to in-ear headphones, semi-in-ear designs are inherently more sensitive to subtle changes in fit during everyday use. Even simple movements such as walking or talking can slightly alter the position of the headphones in the ear, and therefore the path of sound into the ear canal. Because ANC relies on precisely calibrated signals, even such minimal shifts can affect sound leakage, acoustic pathways, and sound pressure within the ear canal, making it difficult for traditional algorithms to maintain consistent noise cancellation performance.
To improve stability under various wearing conditions, Enco Air5s combines OPPO's ergonomic semi-in-ear fit design with real-time adaptive noise cancellation technology.
The result is the ergonomic design of the Enco Air5s earbuds, designed with a larger contact area with the ear and a shallower insertion depth into the ear canal. By evenly and naturally distributing contact across the ear while reducing pressure inside the ear canal, this design provides a comfortable fit, improves wearing stability, and reduces the likelihood of sound leakage during movement.
Building on this ergonomic foundation, the Enco Air5s utilizes OPPO’s Real-Time Adaptive Noise Cancelling technology to dynamically respond to changing acoustic conditions. With an 800kHz ultra-high-frequency sampling system, the headphones continuously analyze wearing style, ear canal characteristics, and ambient noise in real time. This allows the system to more quickly detect subtle acoustic changes and dynamically adjust filter parameters, anti-noise phase alignment, and attenuation depth with greater precision.
OPPO has also optimized several key components in the noise cancellation system, including low-frequency anti-noise output, phase stability, feedback microphone response, and high-frequency sound suppression (anti-howling) efficiency. The noise cancellation system's efficiency is also confirmed by certification from TÜV Rheinland, further highlighting OPPO's efforts to improve ANC performance in the semi-in-ear form factor.
This balance becomes even more important in earbud designs, where the open structure makes both noise control and sound tuning more difficult. To help maintain sound quality with noise cancellation enabled, the Enco Air5s feature Adaptive Sound Enhancement technology.
“The system continuously analyzes both the audio being played and the sound leakage caused by the open fit structure,” said Fei Xia. “Based on these real-time calculations, the headphones dynamically compensate for different frequency ranges, especially low frequencies, which are more prone to dissipation in earcup designs.” For the user, the result of all this careful engineering is that the Enco Air5s are able to maintain richer bass, more natural vocals, and a stable overall sound quality even with ANC turned on.
The Enco Air5s are not just OPPO's first in-ear headphones with active noise cancellation; they embody the company's systemic approach to implementing noise cancellation in one of the most technical headphone form factors in the industry.
Combining acoustic architecture, ergonomics, real-time adaptive algorithms, and adaptive sound enhancement, Enco Air5s offer a new quality of in-ear listening experience that is quieter, more stable, and more comfortable in daily use.
