Effects Of Geometry On The Resonance Frequency Of Helmholtz Resonators

Helmholtz resonators are used to control low-frequency noise in cavities. One of the ways to reduce the resonance frequency of a resonator without changing its volume is to introduce an intrusion. Similarly, the introduction of multiple orifices can increase the resonance frequency without changing the resonator volume. These features provide an ability to accommodate slight changes in the cavity/enclosure frequencies during the design process. However, one has to rely on extensive three-dimensional finite element or boundary element simulations to predict the resonator characteristics with the introduction of these features. To reduce the computational burden, a design relation, between the first resonance frequency of a single orifice intruded resonator with that of a multi-orifice intruded resonator, is proposed in this paper. In developing this design relation, the total cross-sectional area of the resonator with multiple orifices is the same as that of the single orifice resonator. It is shown that this design relation is independent of the shape/size of the orifices and resonator cavity. Using this relation, a new end correction formula for the orifice lengths of multi-orifice intruded resonators has been proposed. The end correction formula can be used to calculate the reactance of multi-orifice intruded Helmholtz resonators analytically. These expressions are derived by carrying out extensive simulations of the resonators using the boundary element method. Limited experiments have been carried out to validate the proposed approach. The use of these expressions will reduce the computational cost of simulating cavities embedded with resonators as one can avoid modeling the resonators and use impedance boundary conditions instead.

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Impact of Density Discontinuities on the Resonance Frequency of Helmholtz Resonators

AIAA Journal ◽

10.2514/1.j053227 ◽

2015 ◽

Vol 53 (4) ◽

pp. 877-887 ◽

Cited By ~ 10

Author(s):

Mirko R. Bothien ◽

Dominik Wassmer

Keyword(s):

Resonance Frequency ◽

Helmholtz Resonators

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Damped resonance for broadband acoustic absorption in one-port and two-port systems

Scientific Reports ◽

10.1038/s41598-019-49222-w ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Taehwa Lee ◽

Tsuyoshi Nomura ◽

Hideo Iizuka

Keyword(s):

Porous Media ◽

Resonance Frequency ◽

Porous Materials ◽

Acoustic Energy ◽

Acoustic Absorption ◽

Practical Applications ◽

Broadband Absorption ◽

Helmholtz Resonators ◽

Port Systems ◽

Lossy Materials

Abstract We demonstrate broadband perfect acoustic absorption by damped resonances through inclusion of lossy porous media. By minimally placing the lossy materials around the necks of single-resonance Helmholtz resonators, where acoustic energy is concentrated, we show an increase in absorption bandwidths (>100% of the resonance frequency). Using the damped resonance, we demonstrate three types of broadband acoustic absorbers in one-port and two-port systems: broadband absorbers (one-port), broadband sparse absorbers (two-port), and broadband duct absorbers (two-port). Our approach for broadband absorption allows to minimize the number of resonances for compact absorbers, while it is beneficial for practical applications owing to the minimum use of porous materials.

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EFFECTS OF GEOMETRY ON THE RESONANCE FREQUENCY OF HELMHOLTZ RESONATORS, PART II

Journal of Sound and Vibration ◽

10.1006/jsvi.1997.0969 ◽

1997 ◽

Vol 204 (5) ◽

pp. 829-834 ◽

Cited By ~ 29

Author(s):

R.C. Chanaud

Keyword(s):

Resonance Frequency ◽

Helmholtz Resonators

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Actuation and dynamic mechanical characteristics of a core free flat dielectric electro-active polymer soft actuator

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.4.2020.08.0582 ◽

2020 ◽

Vol 14 (4) ◽

pp. 7396-7404

Author(s):

Abdul Malek Abdul Wahab ◽

Emiliano Rustighi ◽

Zainudin A.

Keyword(s):

Theoretical Model ◽

Resonance Frequency ◽

Dynamic Testing ◽

Experimental Results ◽

Percentage Error ◽

Initial Tension ◽

Average Percentage ◽

Soft Actuator ◽

Average Percentage Error ◽

Mechanical Dynamics

Various complex shapes of dielectric electro-active polymer (DEAP) actuator have been promoted for several types of applications. In this study, the actuation and mechanical dynamics characteristics of a new core free flat DEAP soft actuator were investigated. This actuator was developed by Danfoss PolyPower. DC voltage of up to 2000 V was supplied for identifying the actuation characteristics of the actuator and compare with the existing formula. The operational frequency of the actuator was determined by dynamic testing. Then, the soft actuator has been modelled as a uniform bar rigidly fixed at one end and attached to mass at another end. Results from the theoretical model were compared with the experimental results. It was found that the deformation of the current actuator was quadratic proportional to the voltage supplied. It was found that experimental results and theory were not in good agreement for low and high voltage with average percentage error are 104% and 20.7%, respectively. The resonance frequency of the actuator was near 14 Hz. Mass of load added, inhomogeneity and initial tension significantly affected the resonance frequency of the soft actuator. The experimental results were consistent with the theoretical model at zero load. However, due to inhomogeneity, the frequency response function’s plot underlines a poor prediction where the theoretical calculation was far from experimental results as values of load increasing with the average percentage error 15.7%. Hence, it shows the proposed analytical procedure not suitable to provide accurate natural frequency for the DEAP soft actuator.

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Observation of Magnetoelectric Effect and Tuning of Ferromagnetic Resonance Frequency using Bilayers Formed of Bulk YIG and PMN-PT

10.1557/proc-1110-c06-34 ◽

2008 ◽

Author(s):

Jacob H. Leach ◽

Vladimir Kovalskii ◽

Vitaliy Avrutin ◽

Ümit Özgür ◽

Hadis Morkoç

Keyword(s):

Resonance Frequency ◽

Ferromagnetic Resonance ◽

Magnetoelectric Effect ◽

Ferromagnetic Resonance Frequency

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Influence of Bone Quality, Drilling Protocol, Implant Diameter/Length on Primary Stability: An In Vitro Comparative Study on Insertion Torque and Resonance Frequency Analysis

Journal of Oral Implantology ◽

10.1563/aaid-joi-d-19-00145 ◽

2020 ◽

Vol 46 (3) ◽

pp. 182-189 ◽

Cited By ~ 1

Author(s):

Davide Farronato ◽

Mattia Manfredini ◽

Michele Stocchero ◽

Mattia Caccia ◽

Lorenzo Azzi ◽

...

Keyword(s):

Resonance Frequency ◽

Bone Quality ◽

Frequency Analysis ◽

Primary Stability ◽

Mean Difference ◽

Insertion Torque ◽

Resonance Frequency Analysis ◽

Bone Response ◽

Implant Length

The aim of this study was to evaluate the influence of bone quality, drilling technique, implant diameter, and implant length on insertion torque (IT) and resonance frequency analysis (RFA) of a prototype-tapered implant with knife-edge threads. The investigators hypothesized that IT would be affected by variations in bone quality and drilling protocol, whereas RFA would be less influenced by such variables. The investigators implemented an in vitro experiment in which a prototype implant was inserted with different testing conditions into rigid polyurethane foam blocks. The independent variables were: bone quality, drilling protocol, implant diameter, and implant length. Group A implants were inserted with a conventional drilling protocol, whereas Group B implants were inserted with an undersized drilling protocol. Values of IT and RFA were measured at implant installation. IT and RFA values were significantly correlated (Pearson correlation coefficient: 0.54). A multivariable analysis showed a strong model. Higher IT values were associated with drilling protocol B vs A (mean difference: 71.7 Ncm), implant length (3.6 Ncm increase per mm in length), and substrate density (0.199 Ncm increase per mg/cm3 in density). Higher RFA values were associated with drilling protocol B vs A (mean difference: 3.9), implant length (1.0 increase per mm in length), and substrate density (0.032 increase per mg/cm3 in density). Implant diameter was not associated with RFA or IT. Within the limitations of an in vitro study, the results of this study suggest that the studied implant can achieve good level of primary stability in terms of IT and RFA. A strong correlation was found between values of IT and RFA. Both parameters are influenced by the drilling protocol, implant length, and substrate density. Further studies are required to investigate the clinical response in primary stability and marginal bone response.

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