Low frequency noise sources are increasingly present in guided flows, particularly in aeronautics where new engine architectures are driven by the reduction of energy consumption. Current acoustic treatments present a conflict between achieving both high acoustic and aerodynamic performance while respecting the constraints of reduced lined surface, low thickness and low embarked weight.

Energy efficiency has been identified as one of the key pillars of decarbonisation in the Net Zero Emissions by 2050 roadmap. It should be specially considered for the development of sustainable cities, as almost 80 % of the population lives in towns and consumes 78% of the primary energy.

Land transport and aeronautical industries are currently faced with the challenge of the design of lightweight and compact acoustic materials capable of reducing under flow the low and medium frequency components (< 1 kHz) of surrounding noise sources. Current treatments for reducing internal and external noise are based on the use of acoustic resonators and porous materials whose effectiveness covers the medium and high frequency ranges. The search for passive acoustic treatments with low embarked mass and capable of reducing low frequencies remains an open problem.

Transportation noise has become a major concern for residents in urban environments, giving rise to stacked legislation at various levels. Current noise reduction technologies do not seem to be sufficient to achieve the targeted reduction. Noise abatement classical procedures add additional weight. Active technologies are mainly applied to downscaled models components and have a moderate technology readiness level.

The problem of lightweight and space-constrained sound absorbers in the low frequency range constitutes an area of continuous research. For instance, aeronautics has an important role to play in reducing noise to support sustainable traffic growth: one of the main challenges of air transport is to attenuate the environmental impact of air traffic despite its continuing expansion. Passive methods can provide significant noise reduction, but also additional weight and may obstruct fast routine maintenance inspection.

As a consequence of the continuous air transport growth and to comply with stringent environmental regulations, there is a strong demand for the development of novel noise reduction techniques in the aeronautical sector at an acceptable cost and weight. The general objective of this project is to design innovative surface treatments that would be applied on portions of aircraft fuselage and wings in order to reduce the exposure of the community to airborne and airframe noise sources.

Road traffic noise amounts to roughly half of the overall ambient noise. Usual emission (vehicle emission limits) and immission (barriers, sound-reducing windows) noise control techniques have not been enough to decrease significantly the annoyance by road traffic over the last three decades. The positive effect of these control techniques has been counteracted by the increase of traffic density. Moreover, the traffic noise annoyance is highly correlated with the maximum noise levels usually produced by aggressive drivers. However, current traffic noise measurement systems are based upon an overall assessment, so that they are unable to discriminate between quiet and noisy drivers. Therefore, a near field noise measuring system is proposed in this research that is able to measure the contribution of each vehicle to the road traffic noise, allowing the detection of noisy drivers.  The system is based on two onboard microphones, one for the engine noise and other for the rolling noise.