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Analyze ANC and ENC concepts in TWS headphones

Among the key performance of TWS earphone, noise reduction is one of the key performance. What are ANC and ENC concepts of noise reduction respectively?  How does that work?


ANC stands for Active Noise Cancellation.  Interference occurs when sound waves from two sources with the same frequency and direction of vibration are superimposed on each other.  If the two sources are in opposite phase, the sound waves add up to decrease in amplitude and decrease in pressure.  If two sound waves have the same amplitude, they cancel out completely.  ANC makes use of the phenomenon of acoustic wave cancellation interference. Its working principle is that the earphone generates an acoustic wave with equal frequency and amplitude but opposite phase according to the collected noise, and then the speaker plays it in the ear canal.  Finally, what people hear is the superposition of ambient noise and the inverted ambient noise.  So it sounds like less noise.  ANC mainly reduces low and medium frequency noise in the environment.  So that consumers even in a noisy environment, do not need to raise the volume, still can enjoy music.


ENC's full name is Environmental Noise Cancellation.  ENC includes single wheat environment noise reduction and double wheat environment noise reduction.  Ambient noise estimation is usually based on the premise that ambient noise is stochastic stationary additive noise and unrelated to speech signal, and then the noise is filtered.  Therefore, the noise reduction effect of single wheat environment is relatively poor.  Dual-mic environment noise reduction is to accurately calculate the speaking orientation of the caller through the dual-mic array, while protecting the target voice, filter out various interference noises in the environment.  Its working principle is roughly as follows: before calculating the ambient noise filter module, the gain of the speech microphone and reference microphone and the delay of the two microphones are corrected.  Then it detects whether the data collected by the voice microphone is a speech segment.  If it is a voice segment (uplink call), the ambient noise is estimated according to the ambient noise collected by the reference microphone and the voice data of the voice microphone, and the corresponding noise suppression parameters are calculated. Finally, the ambient noise is filtered out by the filter module.  Otherwise, no ambient noise filtering is performed and the uplink call output is muted.  ENC reduces non-target voice noise during a call to ensure a clear call.


Keywords:TWS, noise reduction