Active Noise
Cancellation
What is Active Noise Cancellation
Active Noise Cancellation (ANC) is a technology designed to reduce unwanted ambient sounds in environments such as crowded streets, busy offices, or noisy transportation. In the context of hearables, ANC refers to the ability of earbuds or headphones to actively counteract external noises, providing users with a more immersive and distraction-free listening experience.
ANC works by employing microphones to pick up external sounds, analyzing them, and generating anti-noise signals that are played through the earphones. These anti-noise signals are precisely tuned to cancel out the incoming noise, effectively diminishing its impact on the user’s auditory experience.
There are typically two types of ANC: feedforward and feedback ANC. Feedforward ANC involves microphones placed outside the earbuds, capturing external sounds before they reach the user’s ears. Feedback ANC, on the other hand, utilizes microphones inside the earbuds to detect the sound that has already reached the user’s ears. Both methods have their advantages and are often used in combination to achieve optimal noise cancellation performance.
What are the key parameters in Dolphin ADC & DAC ?
Latency degrade ANC performances:
System latency limits the perfomance of noise cancellation achievable by an ANC system.
In feedforward systems if the anti-noise signal arrive to late it will not effectivly the embient noise. Which results in auditory genes especially in the high frequencies.
In feedback systems, excessive latency makes the closed-loop system unstable, limiting the performance of the reduction by several dB. This leads to a degradation in noise suppression performance.
In all cases, latency will reduce the level of performance, creating residual noise that can interfere with the experience of final user.
Noise level degrade ANC performances:
Input-referred noise (ADC) and output noise (DAC) are key parameters to perform efficient ANC. The noise captured is greatly amplified in the ANC system.
To quickly estimate the average noise in an ANC system you can use the following equation:
√[((N_ADC1 ∗ FF Gain)^2 + (N_ADC2 ∗ FB Gain)^2 + N_DAC^2)]
This amplified noise is directly audible when the ANC mode is activated if it is too loud.
ADC/DAC Latency
ADC: 3 µs
DAC: 2 µs
ADC/DAC Noise
ADC: 2,6 µVrms
DAC: 1,78 µVrms