Patent ID: 11942104
Assignee: TEAM VIEWER GERMANY GMBH
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 8:
9. A device for enhancing an audio signal in a full duplex audio communication system, the device comprising:
a) a communication input configured to receive a far end audio signal;
b) an audio speaker to which the far end audio signal is forwarded;
c) a microphone configured to receive a near end audio signal;
d) an echo reduction component within a signal enhancement chain performing an echo reduction on the near end audio signal using the far end audio signal;
e) a communication output to which the near end audio signal is forwarded after the echo reduction; and
f) a half-duplex safeguard, which
determines whether a residual echo still exists in the near end audio signal after the echo reduction, wherein, for determining the existence of residual echo, a residual echo existence estimator compares the near end audio signal after the echo reduction with the far end audio signal again, and
if the existence of residual echo is determined
attenuates the near end audio signal,
deactivates its forwarding to the communication output, and/or
adjusts at least one parameter of the signal enhancement chain,

wherein the residual echo existence estimation compares the near end audio signal and the far end audio signal in a frequency domain and statistically analyzes the outcome,
wherein estimating the existence of residual echo comprises transferring time slots of the near end audio signal and the far end audio signal into the frequency domain thereby providing a plurality of time step dependent near end spectra and a plurality of time step dependent far end spectra,
wherein each time step dependent near end spectrum is compared to a plurality of time delayed versions of the time step dependent far end spectra by calculating a distance value d between the time step dependent near end spectrum and each of the plurality of time step dependent far end spectra, and
wherein calculating the distance value d is defined as:

d(X,Y)=∥N(C(X))−N(C(Y))∥

wherein X stands for the near end spectrum and Y for the far end spectra and where
C(X)=frequency window function keeping only an inner part of a spectrum between a first and second cutoff frequency
N(X)=X− mean(X)=zero-mean version of X with mean(X)=ΣωX[ω]/Σω1
∥X∥=√{square root over (ΣωX[ω]2)}=Euclidean vector norm of X.