A two-microphone method for the determination of the mode amplitude distribution in high-frequency ducted broadband sound fields

Joseph, Phillip

doi:10.1121/1.5004568

Cited by 7 publications

(9 citation statements)

References 14 publications

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“…It is based on previous work by (author?) [9] in which the mode amplitude distribution may be determined as a function of cut-on ratio α from measurements of the coherence function between the acoustic pressures at two closely spaced microphones at the duct wall. Central to the formulation of the method is (2) linking k to α for a uniform mean axial flow.…”

Section: A New Two-microphone Methodsmentioning

confidence: 99%

“…The formulation in (author?) [9] is therefore restricted to the idealised case of uniform mean flow.…”

Section: A New Two-microphone Methodsmentioning

confidence: 99%

“…One such example of this approach is in a new measurement procedure, referred to here as the twomicrophone method [9], which allows the mode amplitude distribution to be deduced as a function of α from measurements of the coherence function between two acoustic acoustic measurements made at the duct wall. However, this method based on α is restricted to a uniform axial mean flow.…”

Section: Mode Distribution Function For Cut-on Ratiomentioning

confidence: 99%

“…In a hollow duct with uniform axial flow, in the high-frequency limit, work by (author?) [9,12,1] have shown analytically that α has the following distribution…”

Section: Mode Distribution Function For Cut-on Ratiomentioning

confidence: 99%

“…Finally, its application to the new two-microphone method recently proposed by (author?) [9] is investigated in which the concept of cut-on ratio and its simple relationship to the modal axial wavenumber is central. Here we show that this method, which aims to determine the distribution of mode amplitudes versus cut-on ratio, breaks down.…”

Section: Introductionmentioning

confidence: 99%

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Modal cut-on ratio in ducts with realistic flow profiles and its application to acoustic mode detection

Mathews

Chen

Joseph

2018

Journal of Sound and Vibration

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This paper considers the modal cut-on ratio and its use in acoustic mode detection in ducts for a radially varying flow with swirl. These concepts have previously only been considered for the idealised case of uniform axial mean flow and no swirl, and thus in this paper they are generalised and extended to account for radial variations in axial and swirl Mach numbers. The cut-on ratio is shown to no longer satisfy a simple relation with the axial wavenumber, showing that while the cut-on ratio in arbitrary flow is defined its usefulness significantly decreases. Mode distribution functions are also investigated for radially varying flows, both in terms of cut-on ratio and axial wavenumber. In view of the deficiencies of the cut-on ratio highlighted in the paper a recent method for mode detection in ducts that uses just two microphones is generalised to deduce the mode amplitudes in radially varying flows, based on modal axial wavenumber rather than cut-on ratio. This method is shown to perform better than the existing method in radially varying and/or swirling flow in simple test configurations with an idealised source distribution.

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Section: A New Two-microphone Methodsmentioning

confidence: 99%

“…The formulation in (author?) [9] is therefore restricted to the idealised case of uniform mean flow.…”

Section: A New Two-microphone Methodsmentioning

confidence: 99%

Section: Mode Distribution Function For Cut-on Ratiomentioning

confidence: 99%

“…In a hollow duct with uniform axial flow, in the high-frequency limit, work by (author?) [9,12,1] have shown analytically that α has the following distribution…”

Section: Mode Distribution Function For Cut-on Ratiomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modal cut-on ratio in ducts with realistic flow profiles and its application to acoustic mode detection

Mathews

Chen

Joseph

2018

Journal of Sound and Vibration

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Development of New Sound Insulation Simulation Technology Using Finite Element Method for Efficiency of High Aspect Ratio Core in Low Frequency Range

Aya¹,

Hagiwara²

2022

IJMEA

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Nowadays, meta-materials are being studied to reduce vehicle interior noise. But it has not yet been found effective meta-materials at low frequencies below 500Hz. A panel with one core which has an excellent sound insulation where the higher the height of the core, the better the sound insulation characteristics have been founded. And so, depending on the core height, a structure with one core which is effective even at 500hz or less may be obtained. If the core height is high, it cannot be obtained by press forming, so the origami forming has been developed. Use of FEM which is versatile for shape of structure is effective for analysis of the plate with core or with sound absorbing material. Although the FEM analysis for sound insulation analysis was difficult, so far, two methods have been developed. Here these two methods to a flat plate and a flat plate with sound absorbing material to grasp their characteristics are compared and applied. And then the more versatile method is selected for sound insulation analysis to plates with one core which are formed by origami forming. As a result, it is shown that a plate with one core is effective for sound insulation characteristics at the low frequency below 500Hz depending on the balance between plate thickness and core height. At last, it is shown the core shape that maximizes the integral value of the sound insulation characteristic from 0 Hz to 500 Hz by an optimal analysis.

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High-frequency ducted broadband acoustic mode detection in the swirling flows

Venkateswaran

Joseph

Paruchuri

2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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A two-microphone method for the determination of the mode amplitude distribution in high-frequency ducted broadband sound fields

Cited by 7 publications

References 14 publications

Modal cut-on ratio in ducts with realistic flow profiles and its application to acoustic mode detection

Modal cut-on ratio in ducts with realistic flow profiles and its application to acoustic mode detection

Development of New Sound Insulation Simulation Technology Using Finite Element Method for Efficiency of High Aspect Ratio Core in Low Frequency Range

High-frequency ducted broadband acoustic mode detection in the swirling flows

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