Resonant frequency of an adjustable Helmholtz resonator in a hydraulic system

2008 ◽  
Vol 79 (12) ◽  
pp. 1115-1125 ◽  
Author(s):  
Lari Kela
Keyword(s):  
Resonant Frequency ◽  
Hydraulic System ◽  
Helmholtz Resonator

scholarly journals Acoustic notch filtering earmuff utilizing Helmholtz resonator arrays

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258842
Author(s):  
Fumiya Mizukoshi ◽  
Hidetoshi Takahashi
Keyword(s):  
Resonant Frequency ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Honeycomb Structure ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Target Frequency ◽  
Notch Filtering

In recent years, noisy bustling environments have created situations in which earmuffs must soundproof only specific noise while transmitting significant sounds, such as voices, for work safety and efficiency. Two sound insulation technologies have been utilized: passive noise control (PNC) and active noise control (ANC). However, PNC is incapable of insulating selective frequencies of noise, and ANC is limited to low-frequency sounds. Thus, it has been difficult for traditional earmuffs to cancel out only high-frequency noise that people feel uncomfortable hearing. Here, we propose an acoustic notch filtering earmuff utilizing Helmholtz resonator (HR) arrays that provides a sound attenuation effect around the tuneable resonant frequency. A sheet-like sound insulating plate comprising HR arrays is realized in a honeycomb structure. Since the resonant frequency is determined by the geometry of the HR arrays, a highly audible sound region can be designed as the target frequency. In this research, the acoustic notch filtering performance of the proposed HR array plate is investigated in both simulations and experiments. Furthermore, the fabricated earmuffs using the novel HR array plates achieve a sound insulation performance exceeding 40 dB at the target frequency, which is sufficiently high compared to that of conventional earmuffs. The experimental results confirm that the proposed device is a useful approach for insulating frequency-selective sound.

scholarly journals Geometry Effects on the Noise Reduction of Helmholtz Resonators

2012 ◽  
Author(s):  
M. Farooqui ◽  
A. Alhamoud ◽  
A. Aliuddin ◽  
S. Mekid
Keyword(s):  
Resonant Frequency ◽  
Noise Reduction ◽  
Degrees Of Freedom ◽  
Helmholtz Resonator ◽  
Shape Effect ◽  
Noise Attenuation ◽  
Two Degrees Of Freedom ◽  
Helmholtz Resonators ◽  
Geometry Effects

In this paper the effect of geometry shape of the Helmholtz resonator on its resonant frequency and on its noise attenuation capability is discussed. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one and two degrees of freedom. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.

scholarly journals Measurement of an Analyte Concentration in Test Solution by Using Helmholtz Resonator for Biosensor Applications

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1127 ◽  
Author(s):  
Yugang Chen ◽  
Yong-Hwa Park
Keyword(s):  
Resonant Frequency ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Acoustic Resonance ◽  
Acoustic Power ◽  
Test Solution ◽  
Frequency Change ◽  
Analyte Concentration ◽  
Resonator System ◽  
Higher Sensitivity

In this paper, an indirect method of measuring an analyte concentration in a test solution using the resonant frequency change of a Helmholtz resonator is proposed, using a novel architecture of Helmholtz resonator filled with two kinds of fluids (fixed fluid and test solution). Since the analyte concentration yields changes of density and sound speed of the test solution, the resonant frequency of the proposed Helmholtz resonator is affected by the analyte concentration of the test solution. From this effect, the analyte concentration of the test solution can be measured by the spectrum of acoustic resonance of the Helmholtz resonator. The experiment was done using a 3D-printed Helmholtz resonator system with an acoustic power source and detectors, which is consistent with analytical results and showed that the analyte concentration can be measured with higher sensitivity compared to conventional cantilever-type sensors. As an example application, the possibility of measuring glucose concentration of human blood was demonstrated, showing higher sensitivity and relatively low frequency range compared to previous resonance based methods.

A Tunable Helmholtz Resonator for Active Noise Control

2013 ◽  
Author(s):  
Shahin S. Nudehi ◽  
Stephen Charnley ◽  
Taylor Brandt ◽  
Parisa Nasserifar
Keyword(s):  
Mathematical Modeling ◽  
Differential Equations ◽  
Resonant Frequency ◽  
Nonlinear Differential Equations ◽  
Helmholtz Resonator ◽  
Primary System ◽  
Membrane Tension ◽  
Analytical Formulation ◽  
Active Noise ◽  
Tunable Resonator

In this study, a tunable Helmholtz resonator is proposed for active noise cancelation in a primary acoustic system. In the tunable Helmholtz resonator, the resonator’s top wall is replaced by a flexible membrane and four actuators are mounted on the side of the resonator. These actuators are connected to the membrane in order to tune its radial force (tension) by pulling or releasing the membrane during the operation. This causes the resonant frequency of the modified Helmholtz resonator to change due to the change in the membrane tension. The maximum noise attenuation is achieved when the the resonant frequency of the active resonator matches with the noise frequency in the primary system. In this paper, first mathematical modeling is used to derive nonlinear coupled differential equations for the tunable Helmholtz resonator with the membrane. The differential equations were linearized to obtain an analytical formulation for the resonant frequency of the tunable resonator in terms of the membrane tension. The analytical formulation for the resonant frequency was verified via simulation of the original nonlinear differential equations. Finally, to demonstrate the validity of the mathematical modeling of the tunable resonator, experimental results are provided.

scholarly journals Numerical investigation on low-frequency noise damping performances of Helmholtz resonators with an extended neck in presence of a grazing flow

2021 ◽  
pp. 146134842110205
Author(s):  
Weiwei Wu ◽  
Yiheng Guan
Keyword(s):  
Resonant Frequency ◽  
Stokes Equations ◽  
Transmission Loss ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Frequency Noise ◽  
Frequency Range ◽  
Helmholtz Resonators ◽  
Numerical Predictions ◽  
Grazing Flow

In this work, modified designs of Helmholtz resonators with extended deflected neck are proposed, numerically evaluated and optimized aiming to achieve a better transmission loss performance over a broader frequency range. For this, 10 Helmholtz resonators with different extended neck configurations (e.g. the angle between extended neck and the y-axis) in the presence of a grazing flow are assessed. Comparison is then made between the proposed resonators and the conventional one, i.e. in the absence of an extended neck (i.e. Design A). For this, a two-dimensional linearized Navier Stokes equations-based model of a duct with the modified Helmholtz resonator implemented was developed in frequency domain. The model was first validated by comparing its numerical predictions with the experimental results available in the literature and the theoretical results. The model was then applied to evaluate the noise damping performance of the Helmholtz resonator with (1) an extended neck on the upstream side (Design B); (2) on the downstream side (Design C), (3) both upstream and downstream sides (Design D), (4) the angle between the extended neck and the y-axis, i.e. (a) 0°, (b) 30°, and (c) 45°, (d) 48.321°. In addition, the effects of the grazing flow Mach number (Ma) were evaluated. It was found that the transmission loss peaks of the Helmholtz resonator with the extended neck was maximized at Ma = 0.03 than at the other Mach numbers. Conventional resonator, i.e. Design A was observed to be associated with a lower transmission loss performance at a lower resonant frequency than those as observed on Designs B–D. Moreover, the optimum design of the proposed resonators with the extended neck is shown to be able to shift the resonant frequency by approximately 90 Hz, and maximum transmission loss could be increased by 28–30 dB. In addition, the resonators with extended necks are found to be associated with two or three transmission loss peaks, indicating that these designs have a broader effective frequency range. Finally, the neck deflection angles of 30° and 45° are shown to be involved with better transmission loss peaks than that with a deflection angle of 0°. In summary, the present study sheds light on maximizing the resonator’s noise damping performances by applying and optimizing an extended neck.

scholarly journals Influence of cavity wall elasticity on resonant frequency of small underwater cylindrical Helmholtz resonator

2009 ◽  
Vol 58 (4) ◽  
pp. 2507
Author(s):  
Wang Ze-Feng ◽  
Hu Yong-Ming ◽  
Luo Hong ◽  
Meng Zhou ◽  
Ni Ming ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Helmholtz Resonator ◽  
Cavity Wall

THE SCALING OF SONG FREQUENCY IN CICADAS

1994 ◽  
Vol 191 (1) ◽  
pp. 291-294 ◽  
Author(s):  
H Bennet-Clark ◽  
D Young
Keyword(s):  
Resonant Frequency ◽  
Sound Production ◽  
Abdominal Cavity ◽  
Helmholtz Resonator ◽  
Ventral Surface ◽  
Recent Model ◽  
End Effect ◽  
Thin Walled ◽  
Song Frequency ◽  
Pressure Changes

In male cicadas, sound is generated by a pair of tymbals on the abdomen (Pringle, 1954). The tymbals buckle inwards causing pressure changes in the abdominal cavity, from which sound is radiated through the tympana (Young, 1990). A recent model of sound production in cicadas suggests that the abdominal cavity and tympana act as the components of a Helmholtz resonator that is excited by the drive from the tymbals (Bennet-Clark and Young, 1992). A Helmholtz resonator consists of a cavity open to the outside via a hole which has a real or notional neck, and the resonant frequency fo is given by the general equation: where c is the speed of sound in the fluid, taken as 340 m s-1 for air, A is the area of the neck, L is the length of the neck and V is the volume of the cavity. Where the resonator has two holes, these terms should be somewhat modified: A is the combined area of the two holes, L is 16/3pi r (~1.7r) for a simple hole in a thin-walled vessel and r is the radius of one hole (Seto, 1971). These modifications to equation 1, which include corrections for the acoustic end-effect at either side of a simple hole in the wall of a vessel, are applicable to a model of the male cicada, in which there are two tympana close to the ventral surface of the abdomen.

Tuned Damping of an Air-Mounted Isolation System

2004 ◽  
Author(s):  
Reza Kashani ◽  
Kazim Mirza
Keyword(s):  
Resonant Frequency ◽  
High Frequency ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Isolation System ◽  
And Mathematics ◽  
High Level ◽  
Three Degree Of Freedom ◽  
Tuned Damper ◽  
Isolation Performance

Air mounts can provide the highest degree of isolation of any type vibration isolator. Soft-mounting, and thus high level of low-frequency isolation, with system natural frequency as low as 1 Hz can be achieved. Due to their construction, air mounts have negligible damping. Although, this almost undamped nature of air mounts enhances the high-frequency isolation, provisions should be made to address the lack of isolation resulting in excessive body displacements around the resonant frequencies, especially when the system is exposed to shock inputs. While the addition of viscous damping to the air mount is proposed in the literature but it is not recommended in most applications. This is because it deteriorates the mount’s high-frequency isolation performance. Instead, it would be highly desirable to add tuned damping to the mounted system at its resonant frequency (ies). The challenge in doing so, is realizing a damper tunable to a very low frequency and yet not be prohibitively large. A novel tuned damping mechanism is proposed in this paper. It adds damping to an air mount only at the resonant frequency (ies), via a bi-fluid Helmholtz resonator. In an illustrative example the mechanics and mathematics (modeling) of a one and three degree of freedom air mounted systems equipped with a tuned damper, as well as the tuning of such damper are discussed. The example also demonstrates the effectiveness of the air mount with the tuned damper.

scholarly journals Acoustic notch filtering earmuff utilizing Helmholtz resonator arrays

2021 ◽  
Author(s):  
Fumiya Mizukoshi ◽  
Hidetoshi Takahashi
Keyword(s):  
Resonant Frequency ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Honeycomb Structure ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Target Frequency ◽  
Notch Filtering

Abstract In recent years, noisy bustling environments have created situations in which earmuffs must soundproof only specific noise while transmitting significant sounds, such as voices, for work safety and efficiency. Two sound insulation technologies have been utilized: passive noise control (PNC) and active noise control (ANC). However, PNC is incapable of insulating selective frequencies of noise, and ANC is limited to low-frequency sounds. Thus, it has been difficult for traditional earmuffs to cancel out only high-frequency noise that people feel uncomfortable hearing. Here, we propose an acoustic notch filtering earmuff utilizing Helmholtz resonator (HR) arrays that provides a sound attenuation effect around the tuneable resonant frequency. A sheet-like sound insulating plate comprising HR arrays is realized in a honeycomb structure. Since the resonant frequency is determined by the geometry of the HR arrays, a highly audible sound region can be designed as the target frequency. In this research, the acoustic notch filtering performance of the proposed HR array plate was investigated in both simulations and experiments. Furthermore, the fabricated earmuffs using the novel HR array plates achieved a sound insulation performance exceeding 40 dB at the target frequency, which is sufficiently high compared to conventional earmuffs. The experimental results confirm that the proposed device is a useful approach for insulating frequency-selective sound.

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