Remote Sensing for a Lining Integrated Active Structural Acoustic Control System


== Abstract ==

In the framework of the EU project ACASIAS an aircraft sidewall panel (lining)
with structurally integrated actuators and sensors is developed. Each lining has a digital unit
which samples the sensor signals, performs filtering operations and supplies the actuators with
control signals. The whole system makes up an active structural acoustic control system aiming
at the reduction of low-frequency multi-tonal aircraft interior noise. The novelty of this
approach compared to past implementations of active noise control (ANC) systems in aircraft
is its modularity. Each so-called smart lining is autonomous in the sense that it processes only
structural sensor data from its own integrated sensors. The use of external microphones for error
sensing is avoided because this conflicts with the modularity of the smart lining. Hence, one
important design task is the replacement of the physical error microphones by the integrated
structural sensors and an acoustic filter (observer) running on the digital unit. This method,
which is called the remote microphone technique for active control, has never been applied to
an aircraft interior structure so far. The detailed design of the smart lining module comprises
several steps which are taken within work package 3 of the ACASIAS project. Experimental
data of an aircraft typical double panel system is captured in a sound transmission loss facility.
The system is excited with a loudspeaker array placed directly in front of the fuselage structure.
Different acoustic load cases are used for the definition of the sensors and the actuators. A
multi-tonal excitation with high sound pressure level is relevant for the actuator dimensioning
and a broadband excitation with multiple independent sound sources is relevant for the sensor
definition. 19 accelerometers are mounted on the lining and 20 microphones are placed in
front of it. All sensor signals are sampled simultaneously for deterministic and broadband load
cases. The lining is equipped with two inertial mass actuators which are used for the active
control. Measured frequency response functions of actuators at 39 positions are used for the
optimization of the actuator locations. The measurement data is also used for the derivation of
an observer and for the simulation of a smart lining with remote microphones. In this contribution,
the steps undertaken for the detailed design will be described and simulation results of the
noise reduction performance of the smart lining with remote microphones will be presented.

== Full document ==
<pdf>Media:Draft_Content_517635590-p3-1999-document.pdf</pdf>


== References ==

[1] S. J. Elliott, P. A. Nelson, I. M. Stothers, and C. C. Boucher, “In-flight experiments on the active control of propeller-induced cabin noise,” ''Journal of Sound and Vibration'', vol. 140, no. 2, pp. 219–238, 1990.

[2] C. R. Fuller and J. D. Jones, “Experiments on reduction of propeller induced interior noise by active control of cylinder vibration,” ''Journal of Sound and Vibration'', vol. 112, no. 2, pp.389–395, Jan. 1987.

[3] B. N. Tran and G. P. Mathur, “Aircraft interior noise reduction tests using active trim panels,” in ''Proceedings of Noise-Con'' 96, 1996, pp. 395–400.

[4] M. Misol, T. Haase, S. Algermissen, V. Papantoni, and H. P. Monner, “L¨armreduktion in Flugzeugen mit aktiven Linings,” in ''Smarte Strukturen und Systeme – Tagungsband des 4SMARTS-Symposiums'', 2017, pp. 329–339.

[5] M. Misol, “EXPERIMENTS ON NOISE REDUCTION IN AIRCRAFT WITH ACTIVE SIDEWALL PANELS,” in ''Proceedings of the 25th International Congress on Sound and Vibration'', 2018. [Online]. Available: [https://elib.dlr.de/121168/ https://elib.dlr.de/121168/]

[6] A. Roure and A. Albarrazin, “The remote microphone technique for active noise control,”in ''PROCEEDINGS OF ACTIVE 99: THE INTERNATIONAL SYMPOSIUM ON ACTIVECONTROL OF SOUND AND VIBRATION'', ''VOLS 1 & 2'', 1999, pp. 1233–1244.

[7] J. Cheer and S. Daley, “Active structural acoustic control using the remote sensor method,” ''Journal of Physics: Conference Series'', vol. 744, no. 1, 2016.

<span id='_GoBack'></span>[8] S. Algermissen, S. Meyer, C. Appel, and H. P. Monner, “Experimental synthesis of sound pressure fields for active structural acoustic control testing,” ''Journal of Intelligent Material Systems and Structures'', 2013. [Online]. Available: [http://jim.sagepub.com/content/early/2013/06/20/1045389X13493361.abstract http://jim.sagepub.com/content/early/2013/06/20/1045389X13493361.abstract]

[9] M. Misol, “ACTIVE SIDEWALL PANELS WITH REMOTE MICROPHONE TECHNIQUE FOR AIRCRAFT INTERIOR NOISE REDUCTION,” in ''Proceedings of the 26<sup>th</sup> International Congress on Sound and Vibration, 2019'', (accepted for publication).