Soft dB Zen-Ten User guide - Manual (Page 12)

User manual for the ZEN 3-channel X-LMS controller Soft dB inc.
3.1.2 Subtracting the control output contributions from the reference
signals
As illustrated in Figure 5, the control algorithm includes the evaluation and the
subtraction of the control output contributions from the reference signals. Even with great
precautions during the mechanical design of the control system, noise generated by
control sources can add perturbation noise to the reference signals. To prevent control
instability, where an acoustic system is being controlled and a microphone is being used
for instance, the loudspeakers must be isolated from the reference sensors. This insulation
implies the addition of absorbent material and/or some modifications to the geometry of
the system. These additions and modifications can become an important obstacle limiting
the use of the active control technology. Figure 6, Figure 7 and Figure 8 illustrate a
reference signal with and without the output control contribution subtraction.
Figure 6: Autospectrum of a reference signal (control OFF)
Figure 7: Autospectrum of a reference signal (control ON and subtraction ON)
ZEN User Manual p. 12