Dynamics of the harmonic acoustic pneumatic source for active control of time-varying tonal noise

The Harmonic Acoustic Pneumatic Source (HAPS), a mechanical airflow modulator, is a promising alternative to loudspeakers as secondary sources for the active control of harmonic noise, thanks to its ability to generate high sound pressure levels and to precisely control signal frequency, phase, and amplitude. However, this source requires a specialized control strategy, as it operates through mechanical modulation at a predetermined frequency. Hence, conventional adaptive control techniques are not directly applicable. Furthermore, when dealing with time-varying harmonic noise, the dynamic performance of the control system, which is influenced by the dynamic properties of the HAPS, is challenged. The originality of this study lies in considering this source, not as a tonal source, but as a narrow-band mechanical modulator that generates a narrow-band anti-noise by driving its complex envelope, allowing the active control of time-varying primary noise. A model of the dynamic response of the Harmonic Acoustic Pneumatic Source and of its controller is presented, with an analysis of the theoretical dynamic performances and limitations of this control system. The controller uses either a far-field error microphone or a near-field error microphone with a previously established compensation strategy. The closed-loop model is validated with experimental results. Simulations and experiments of far-field and near-field active noise control on slow time-varying primary noise are conducted to characterize the dynamic performances and limitations of the controller. The simulations are in good agreement with the experimental results. • Detailed modelling and analysis of the dynamic response of a Harmonic Acoustic Pneumatic Source (HAPS) and its associated control system. • The convergence rate of the control system can be significantly improved, within the limitations of the electromechanical components. • The HAPS can quickly attenuate tonal noises that vary slowly in amplitude and phase. • The HAPS can be used as a narrow-band anti-noise source rather than a purely tonal source.