Helmholtz Resonators Acting as Sound Source in Automotive Aeroacoustics

Wickern, Gerhard; Brennberger, Martin

doi:10.4271/2009-01-0183

Cited by 7 publications

(7 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This power law relationship investigation can be extended to determine the dominating noise sources for each third-octave frequency band. Similar investigations have taken place by Wickern and Brenberger (2009b) and Peng (2007). The power parameter in this work is termed the source index, which provides information as to the nature of the aeroacoustic source.…”

Section: Relationship Between Cabin Noise and Flow Speedmentioning

confidence: 76%

“…Loudness can also be approximated through the use of A-weighted SPL, giving an indication of the overall sound level in the cabin. gaps can also generate noise which is proportional to flow speed raised to the fourth power, as described by Wickern and Brenberger (2009a). Near the A-pillar region, it is expected that dipole sound sources dominate and this is shown by Equation 3.4.…”

Section: Cabin Noisementioning

confidence: 98%

“…The flow speed scaling laws of various sound sources were also investigated by Wickern and Brenberger (2009b). By assessing the sensitivity of both exterior and interior noise to flow speed, a valuable insight can be gained into the physics of the sound sources.…”

Section: Introduction and Aimsmentioning

confidence: 99%

“…One reason why body gaps are taped over during aeroacoustic wind tunnel testing is to avoid any gap noise, since body panel gap variation between vehicles can otherwise colour acoustic results. Wickern and Brenberger (2009a) investigated the mechanisms behind this gap noise. This behaviour was related to that of a Helmholtz resonator, with pressure fluctuations from the turbulent boundary layer found to be large enough to excite the fluid within the cavity leading to noise generation.…”

Section: Introduction and Aimsmentioning

confidence: 99%

See 3 more Smart Citations

The Effects of Unsteady On-Road Flow Conditions on Cabin Noise

Oettle¹,

Sims-Williams²,

Dominy³

et al. 2010

SAE Technical Paper Series

View full text Add to dashboard Cite

On-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. There is increasing concern about potential differences between steady flow conditions that are typically used for development and the transient conditions that occur on-road. This work considers whether steady techniques are able to predict the unsteady results measured on-road, the impact of this unsteadiness on the noise perceived in the cabin and whether minor changes made to the geometry of the vehicle could affect this. Both external aerodynamic and acoustic measurements were taken using a full-size vehicle combined with measurements of the noise inside the cabin. Data collection took place on-road under a range of wind conditions to accurately measure the response of the vehicle to oncoming flow unsteadiness, with steady-state measurements taking place in full-scale aeroacoustic wind tunnels.Overall it was demonstrated that, using a variety of temporal and spectral approaches, steady techniques were able to predict unsteady on-road results well enough to assess cabin noise by correctly taking into account the varying on-road flow conditions. Aerodynamic admittance values remained less than unity in the sideglass region of the vehicle, with the exception of the the region nearest the A-pillar. The reducing unsteady energy at frequencies greater than 10 Hz, combined with the corresponding roll-off in admittance, implies that unsteady frequencies below 10 Hz affect the vehicle most, where the response remains quasi-steady.Quasi-steady cabin noise simulations allowed a subjective assessment of the predicted unsteady cabin noise, where the impact of cabin noise modulations were quantified and found to be important to perception. Minor geometry changes affected the sensitivity of cabin noise to changes in yaw angle, altering modulation and therefore having an important impact on the unsteady wind noise perceived on-road.iii DeclarationThe work in this thesis is based on research carried out at the School of Engineering and Computing Sciences, Durham University, UK. No part of this thesis has been submitted elsewhere for any other degree or qualification and it all my own work unless referenced to the contrary in the text.

show abstract

Section: Relationship Between Cabin Noise and Flow Speedmentioning

confidence: 76%

Section: Cabin Noisementioning

confidence: 98%

Section: Introduction and Aimsmentioning

confidence: 99%

Section: Introduction and Aimsmentioning

confidence: 99%

See 2 more Smart Citations

The Effects of Unsteady On-Road Flow Conditions on Cabin Noise

Oettle¹,

Sims-Williams²,

Dominy³

et al. 2010

SAE Technical Paper Series

View full text Add to dashboard Cite

show abstract

“…In addition to isolating noise due to leakage, body gaps are taped over during aeroacoustic wind tunnel testing to avoid any gap noise, since body panel gap variation between individual vehicles can confuse the measurement of other acoustic sources. The underlying mechanism is related to that of a Helmholtz resonator, with pressure fluctuations from the turbulent boundary layer large enough to excite the fluid within the cavity leading to noise generation 76 .…”

Section: Sunroof and Side Windowsmentioning

confidence: 99%

Automotive aeroacoustics: An overview

Oettle

Sims-Williams

2017

Proceedings of the Institution of Mechanical Engineers, Part D:

View full text Add to dashboard Cite

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractVehicle aeroacoustic performance has a strong influence on customer perception and also has importance for safety and comfort. Wind noise performance was once differentiated by the quality of sealing. Today, achieving competitive wind noise performance also depends on minimising aeroacoustic noise sources generated by the vehicle form, and on attenuation in the noise pathway from sources on the exterior to the vehicle interior. Attenuation in the noise pathway from sources on the exterior to the vehicle interior, especially through glazed surfaces, will continue to play an important role in controlling cabin noise, with a particular emphasis on achieving attenuation efficiently in terms of component mass. The human brain is not only sensitive towards the level of steady broadband noise, but distinctive features such as tonality or modulation draw the attention of the vehicle occupant and impact negatively on perception. Complex indices are often required to define good wind noise performance. This includes the consideration of multiple frequency bands and effects of the range of yaw angles experienced on-road. A key to achieving future vehicle refinement is bringing together an understanding of unsteady onset flow conditions, their impact on cabin sound pressure level and modulation and in turn the impact of noise level and modulation on psychoacoustic perception.

show abstract

Sound reduction of side-branch resonators: An energy-based theoretical perspective

Li,

Chang Gea

2024

AIP Advances

View full text Add to dashboard Cite

For over a century, side-branch resonators have served as effective acoustic filters, yet the explanation for their sound reduction capability has varied. This paper introduces a novel theory applicable to all types of side-branch resonators from an energy perspective and explains sound reduction as a consequence of acoustic energy redistribution. Our theory posits that a standing wave inside the resonator induces air vibration at the opening, which then acts as a secondary sound source, emitting acoustic energy predominantly in the form of kinetic energy. Due to the formation process of the standing wave, the sound wave generated by the resonator undergoes a phase shift relative to the original sound wave in the main pipe. Consequently, this generated sound wave, while matching the amplitude, possesses an opposite phase compared to the original noise wave within the main pipe. This antiphase relationship results in the cancellation of sound waves when they interact post-resonator in the main pipe. Our theory, grounded in an energy perspective, is derived from the principles of standing wave vibration and energy conservation.

show abstract

Helmholtz Resonators Acting as Sound Source in Automotive Aeroacoustics

Cited by 7 publications

References 13 publications

The Effects of Unsteady On-Road Flow Conditions on Cabin Noise

The Effects of Unsteady On-Road Flow Conditions on Cabin Noise

Automotive aeroacoustics: An overview

Sound reduction of side-branch resonators: An energy-based theoretical perspective

Contact Info

Product

Resources

About