Low-Noise Design of Medium-Range Aircraft for Energy Efficient Aviation

Promising low-noise aircraft architectures have been identified over the last few years at DLR. A set of DLR aircraft concepts was selected for further assessment in the context of sustainable and energy-efficient aviation and was established at the TU Braunschweig in 2019, the Cluster of Excellence for Sustainable and Energy-Efficient Aviation (SE2A). Specific Top-Level aircraft requirements were defined by the cluster and the selected DLR aircraft designs were improved with focus on aircraft noise, emissions, and contrail generation. The presented paper specifically addresses the reduction of aviation noise with focus on noise shielding and modifications to the flight performance. This article presents the state of the art of the simulation process at DLR and demonstrates that the novel aircraft concepts can reduce the noise impact by up to 50% in terms of sound exposure level isocontour area while reducing the fuel burn by 6%, respective to a conventional aircraft for the same mission. The study shows that a tube-wing architecture with a top-mounted, forward-swept wing and low fan pressure ratio propulsors installed above the fuselage at the wing junction can yield significant noise shielding at improved low-speed performance and reduce critical fuel burn and emissions.

Noise simulation and low noise design of skinned panel structure of scientific experiment rack

The noise of the scientific experiment rack radiates into the space station through the skinned structure, which directly affects the safety and health of astronauts in orbit for a long time, so it is necessary to carry out low-noise design. Firstly, the finite element model of the panel structure is established, and the correctness of the model is verified by modal test. Secondly, select a point as the vibration excitation point on the finite element model of the plate structure to simulate the vibration input of the excitation source, obtain its vibration response through the modal superposition method, take the vibration response as the boundary condition of the acoustic boundary element, use the modal acoustic transfer vector technology to calculate the radiation noise of the plate structure, and verify it through the noise test in the half anechoic chamber. Then, the acoustic pressure contribution analysis of the radiated noise from the skinned panel structure is carried out, and the panel area which can reduce the radiated noise of the target is determined. The constrained damping layer is applied in this area. The results show that the radiated noise at the target position is significantly reduced.

Tonal-Noise Assessment of Quadrotor-Type UAV Using Source-Mode Expansions

The present work deals with the modeling of the aerodynamic sound generated by the propellers of small-size drones, taking into account the effects of horizontal forward flight with negative pitch and of installation on supporting struts. Analytical aeroacoustic formulations are used, dedicated to the loading noise. The fluctuating lift forces on the blades are expanded as circular distributions of acoustic dipoles, the radiated field of which is calculated by using the free-space Green’s function. This provides descriptions of the sound field, valid in the entire space. The stationary mean-flow distortions responsible for the lift fluctuations and at the origin of the sound are estimated from existing numerical flow simulations and from ad hoc models. Installation and forward-flight effects are found to generate much more sound than the steady loading on the blades associated with thrust. Therefore, the models are believed reliable fast-running tools that could be used for preliminary low-noise design through repeated parametric calculations, or for noise-impact estimates corresponding to prescribed urban traffic.

Comparison of Low-Noise Air Nozzles: A Pilot Study

Excessive noise is a global occupational health hazard with considerable social and physiological impact, including noise-induced hearing loss (NIHL) (Nelson et al., 2005). Noise is one of the most common occupational hazards in American workplaces. This study was performed in the Occupational Safety and Ergonomics Program’s Biomechanics Laboratory at Auburn University. The main purpose of this study was to compare the noise levels made by different air nozzles actually used by a bakery facility to nozzles whose manufacturers purported that they produce significantly less noise. Noise levels were determined using a sound level meter, which was positioned at ear level at distances of 5 and 10 feet. At the factory, air pressure (~100 psi) was used to push product downstream and to speed product cooling. The nozzles used were simple pipes or traditional air nozzles with side venting, but not of a “low noise” design. Two nozzles used by the factory were compared to three quieter nozzles. Nozzles were tested for both noise level and for air pressure (pushing force).

A Low Power, Low Noise Amplifier for Recording Neural Signals

The design of a low power amplifier for recording EEG signals is presented. The low noise design techniques are used in this design to achieve low input referred noise that is near the theoretical limit of any amplifier using a differential pair as input stage. To record the neural spikes or local field potentials (LFP’s) the amplifier’s bandwidth can be adjusted. In order to reject common-mode and power supply noise differential input pair need to be included in the design. The amplifier achieved a gain of 53.7dB with a band width of 0.5Hz to1.1 kHz and input referred noise measured as 357 nV_rmsoperated with a supply voltage of 1.0V. The total power consumed is around 3.19µW. When configured to record neural signals the gain measured is 54.3 dB for a bandwidth of 100 Hz and the input referred noise is 1.04µ V_rms. The amplifier was implemented in 180nm technology and simulated using Cadence Virtuoso.