At Teufel, we implemented hybrid ANC ( hybrid Active Noise Cancellation) in our new Real Blue NC headphones to suppress external noise. Here, we explain what ANC is and how it differs from previous noise cancelling concepts.
Why noise reduction is important
We have already touched on the theme of noise cancellation several times on the blog. It’s no wonder that “Active Noise Cancellation” (ANC) promises to virtually get rid of annoying outside noise. Distracting street noise, monotonous humming on transport or whirring noises from ventilation systems are already a thing of the past for users of noise-cancelling headphones.
The Real Blue NC offers the best noise suppression technology with hybrid ANC
How active noise cancellation works
The component that technically removes noise from the audio signal is the ANC controller, which is supported by one or more microphones as sensors. Of course, the ANC controller does not detect the noise directly from its source, but at appropriate frequencies with which noise perceived by us is transmitted. These interfering frequencies are stored in the controller as a filter. The ANC controller “clears” the frequencies from the audio signal before it reaches the ear. The physical process behind ANC is called anti-sound. But, whilst the basic ANC concept remains the same, it can be implemented in several ways: feed-forward, feedback, or hybrid ANC.
Feed-forward ANC – the sensor microphone is on the outside
With feed-forward ANC, the microphone is placed on the outside of the ear piece. The microphone “hears” sounds before they reach the ear and transmits this information to the ANC controller. This then processes the noise and generates the anti-noise before the resulting signal is sent to the tweeter. This all happens in fractions of a second.
The microphone on the outside picks up noise early, so there’s more time to respond and create the “counter-noise”.
Feed-forward ANC has no way to correct itself since it does detect the sound signal output by the ANC controller. If the incidental noise comes from an unfavourable angle, it may inadvertently lead to amplification.
In addition, feed-forward ANC operates within a narrow frequency range. It has little effect on frequencies outwith this range. The microphone on the outside is also more sensitive to wind noise.
Feedback ANC – the sensor microphone is inside
With feedback ANC (analogous feedback information on the sound signal), the sensor is inside the earpiece and in front of the loudspeaker, so that the ANC controller can “hear” the resulting signal in exactly the same way as the listener.
Feedback ANC monitors the sound signal, which the ear also hears, and can therefore already respond to slight variations. Feedback ANC also works with a wider frequency range than feed-forward ANC. Another advantage is that feedback ANC can still reduce noise regardless of the angle to the sound source or if the ears are not completely covered.
For higher frequency transmissions, feedback ANC is not as effective as feed-forward. In rare cases it can actually exacerbate background buzzing noise produced since the sensor and tweeter are so close together. Feedback ANC can also filter out too much bass as noise.
Hybrid-ANC – Inner and outer microphones
As you may expect, a hybrid approach offers the best of both worlds and combines feed-forward and feedback ANC by placing a microphone both on the inside and outside of the earpiece.
The advantages of both ANC concepts are combined in the hybrid form. Hybrid ANC can suppress noise over a wider frequency range, adapt to and correct errors and is less sensitive to sound angle and user wear.
Due to this combination, hybrid ANC is much more complicated to implement and also more expensive to manufacture due to the number of high quality compents (microphones) that are necessary to create this system. Not every manfacturer therefore dares to try it out. But here at Teufel, we dared.
Hybrid-ANC in the Real Blue NC
Our new Real Blue NC over-ear headphones have integrated hybrid ANC, and many other useful features.
- Top-of-the-range, closed-circuit HD Bluetooth headset with active noise cancellation
- Fully improved and updated successor to the popular MUTE BT, with optimised Real Time Noise Cancellation
- Optimal Bluetooth connectivity for high sound quality and ranges of up to 10 m
- Large linear HD drivers with vented rear chambers and neodymium magnets for high levels, less distortion and precise sound representation