Variability of low frequency sound transmission measurements

Bravo, Teresa; Elliott, Stephen J.

doi:10.1121/1.1738452

Cited by 33 publications

(28 citation statements)

References 25 publications

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“…10 The formulation can be readily extended to the synthesis of any random pressure field with prescribed spatial correlation properties as long as the pressure excitations we aim to reproduce are modeled as random processes stationary both in space and time. The general synthesis method is now briefly summarized.…”

Section: A the Synthesis Methodsmentioning

confidence: 99%

“…This variability has been widely studied experimentally through interlaboratory comparisons 3,4 as well as through analytical [5][6][7] and numerical 8,9 investigations. In order to make the measurement of the incident power more reliable at low frequencies, Bravo and Elliott 10 have proposed a novel approach based on the reconstruction of the statistical properties of an acoustic diffuse field over the surface of a test partition using a near-field array of suitably driven loudspeakers. Theoretical results have shown that this approach is efficient in providing a measure of the sound reduction index that only depends on the properties of the panel itself and, at this stage, it would benefit from experimental validations.…”

Section: Introductionmentioning

confidence: 99%

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The experimental synthesis of random pressure fields: Methodology

Bravo

Maury

2006

The Journal of the Acoustical Society of America

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This paper presents a methodology for the off-line reproduction of random pressure fields with given spatial correlation characteristics. The simulation method is first presented, together with an outline of the signal processing techniques required. The design of an experimental setup is then detailed in relation with the nature of the simulated pressure fields. Of particular interest is the laboratory synthesis of three different types of partially correlated random excitations: an acoustic diffuse field, a grazing incident plane wave, and a turbulent boundary layer. The corresponding excitations are generated in a semianechoic chamber over a test panel using a near-field array of 16 loudspeakers driven by a set of optimal signals. The loudspeakers are positioned at a suitable distance above a sufficiently dense grid of microphones close to the simulation surface. The mutually correlated drive signals are determined from both the target correlation properties and the acoustic transfer functions measured between the loudspeakers and the microphones. This approach could provide a cost-effective method of reducing the variation of low frequency sound transmission measurements as well as simulating the propeller-induced noise and the boundary layer noise transmitted through aircraft fuselage structures.

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Section: A the Synthesis Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The experimental synthesis of random pressure fields: Methodology

Bravo

Maury

2006

The Journal of the Acoustical Society of America

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“…The diffuse field assumption is only valid in medium and high frequency ranges, as the sound field at low frequencies is dominated by few normal modes in reverberation chamber (Schroeder, 1996). The recommendation included in annex in ISO 140-3 (1995) to increase the distance between microphone position and room boundaries and sampling of sound field, increasing the number of loudspeaker positions, the averaging time and use of absorbing materials to decrease the reverberation time still becomes inadequate to enhance the reproducibility of results below 100 Hz (Bravo, Elliott, 2004;Roland, 1995;Pedersen et al, 2000). If room volume differs by about 40%, the predicted sound insulation could differ by alteast 3 dB (Maluski, Gibbs, 2000).…”

Section: Low Frequency Diffusion Issuementioning

confidence: 99%

“…If room volume differs by about 40%, the predicted sound insulation could differ by alteast 3 dB (Maluski, Gibbs, 2000). Some studies (Bravo, Elliott, 2004) have tried to investigate about reducing the effect of source room on measured sound reduction index at low frequencies by using a number of suitable driven loudspeakers close to the panel to stimulate a diffuse incident field. The low frequency diffusion is a cumbersome task achieved by scientifically selecting the volume, surface area of reverberation chamber and enhancing the state of diffusion for reducing the spatial variance in the value of sound pressure level and reverberation time observed at various positions in the room.…”

Section: Low Frequency Diffusion Issuementioning

confidence: 99%

Technical Notes: Practical Concerns Associated with Single-Number Ratings in Measuring Sound Transmission Loss Properties of Partition Panels

Garg¹,

Kumar²,

Maji³

2013

Archives of Acoustics

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The paper presents an extensive review investigating the practical aspects related to the use of singlenumber ratings used in describing the sound insulation performance of partition wall panels and practical complications encountered in precise measurements in extensive frequency range from 50 Hz to 5 kHz. SWOT analysis of various single number ratings is described. A laboratory investigation on a double wall partition panel combination revealed the significant dependence of STC rating on transmission loss at 125 Hz attributed to 8 dB rule. An investigation conducted on devising alternative spectrums of aircraft noise, traffic noise, vehicular horn noise and elevated metro train noise as an extension to ISO 717-1 Ctr for ascertaining the sound insulation properties of materials exclusively towards these noise sources revealed that the single-number rating Rw + Ctr calculated using ISO 717-1 Ctr gives the minimum sound insulation, when compared with Rw + Cx calculated using the alternative spectrums of aircraft noise, traffic noise, etc., which means that material provides a higher sound insulation to the other noise sources. It is also observed that spectrum adaptation term Cx calculated using the spectrum of noise sources having high sound pressure levels in lower frequencies decreases as compared to ISO 717-1 Ctr owing to significant dependence of Ctr at lower frequencies.

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“…In [3] two situations are compared. On the one hand panels placed in an infinite baffle, separating semi-infinite acoustic domains.…”

Section: Introductionmentioning

confidence: 99%

Modal-based prediction of sound transmission through slits and openings between rooms

Poblet-Puig

Ferran

2013

Journal of Sound and Vibration

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The transmission of sound through slits and openings between cuboid-shaped rooms is analysed. A deterministic model that describes the pressure fields inside the rooms in terms of eigenfunctions and uses the Dirichlet-to-Neumann technique in order to reproduce the slit effect is presented. An efficient formulation of the problem is obtained thanks to the splitting of the original domain into three domains: sending room, slit, receiving room. The geometry and boundary conditions of the problem can be modelled in detail like in an element-based numerical technique (such as the finite element method) but with smaller computational costs. The model is compared with numerical solutions, existent models and published experimental data. Afterwards it is used to analyse some aspects such as the influence of slit dimensions, opening position, room properties (dimensions and absorption) that cannot be taken into account with the available models. These usually suppose that the slit or opening connects two unbounded acoustic domains.

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Variability of low frequency sound transmission measurements

Cited by 33 publications

References 25 publications

The experimental synthesis of random pressure fields: Methodology

The experimental synthesis of random pressure fields: Methodology

Technical Notes: Practical Concerns Associated with Single-Number Ratings in Measuring Sound Transmission Loss Properties of Partition Panels

Modal-based prediction of sound transmission through slits and openings between rooms

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