Low Frequency Sound Field Reconstruction in Non-rectangular Room: A Numerical Validation

Characterization of sound fields in rooms has always been a challenging task. A faithful reconstruction of sound fields in rooms generally would require an impractically high number of microphones. At low frequencies, where sound field can be modeled as a finite superposition of modes, a combination of Matching Pursuit (MP) and Least-squares optimization can help interpolate the Room Impulse Responses using a relatively small number of measurements. Our research focuses on using this paradigm to obtain the low-frequency information of a room in a broader sense, where the spatial distribution of sound pressure in a non-rectangular reverberating room can be reconstructed and visually analyzed. Several evaluations are performed along the progression of the framework to confirm its validity. The modal parameters estimated by MP are also compared with those obtained by the Rational Fraction Polynomial method (global curve fitting). Finally, the reconstruction of sound field, which leads to the visualization of the spatial distribution of sound pressure at any chosen frequency in the range of study, is validated visually and numerically using a finite element method software for a non-rectangular room model. This demonstration provides an extensive look at the high robustness and reliability of the framework as a whole, which is crucial in terms of its practical implementations for room acoustics practitioners

Primary Evaluation on Growth Performances of Stress Negative Piétrain Pigs Raised in Hai Phong Province of Vietnam

peer reviewedThe present study was carried out on 19 stress negative Piétrain pigs (Pietrain ReHal), consisting of 13 gilts and 6 young boars imported from Belgium, raised in the livestock farm of Dong Hiep (Hai Phong) in order to evaluate growth performances and their adaptability in the North of Vietnam. Results showed that the average body weight of the whole herd at 2, 4, 5.5, and 8.5 months old was 19.05, 51.05, 85.82, and 119.47 kg, respectively. During the growing periods, except the first stage, the male grew faster than the female and the pigs of the CT genotype grew faster than those of CC genotype although the difference was not significant (P>0.05). The average daily gain (ADG) was 528.56 grams for the whole herd. The ADG was higher for the male (546.48 grams) than for the female (520.29 grams), and its was higher for the CT than the CC, but the difference was not statistically significant (P>0.05). The feed conversion ratio (FCR) was 2.69 kg. The estimated lean percentage at 8.5 months old was 64.08%. The results indicate that Piétrain stress negative pigs could develop well on the farm conditions in Hai Phong, Vietnam

The 2017 Dengue virus 1 outbreak in northern Vietnam was caused by a locally circulating virus group

Background: Dengue virus (DENV) is a member of insect vector-borne viruses, and it causes dengue fever. Southeast Asia is the epi-center of dengue fever in the world. The characterization of the virus is essential to identify the transmission and evolution of DENV.Objectives: In 2017, there was an outbreak of Dengue virus type 1 (DENV1) in northern Vietnam and the neighboring countries. To identify the genetic character of the outbreak virus in the area, we conducted whole-genome sequencing analysis on the samples positive for the DENV1 along with real-time PCR.Study design: In total, 1026 blood samples were collected from patients with suspected dengue fever in Ha Nam and Hai Duong province, nearby areas of the capital of Vietnam. After screening by real-time PCR, 40 of DENV1 positive samples were subjected to whole-genome sequencing, and 28 complete coding sequences were obtained.Results: All 28 sequences were genotype I of DENV1, which is dominant in the southeast and East Asian countries. The phylogenetic analysis of the E region showed that they fell into a single cluster with the reported sequences from Vietnam between 2009 and 2016, in which the isolates from other countries are very rare. Our results suggested that the 2017 outbreak in the area was caused by locally circulating viruses

Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke

Sound field reconstruction in a room using low-rank approximation of mode shapes: validation and application

Sound field reconstruction in rooms is a subject of high interest in the domain of acoustic research.At low frequencies, a thorough understanding of sound field distribution is the key to identifying im-balance and irregularities caused by the room which will eventually lead to the coloration of sounds.Traditionally, an accurate rendering of the sound field would require an impractically high numberof microphone measurements at multiple locations in the room. Our research tackles this issue byexploiting the sparsity in modal decomposition expression of the sound field with the use of low-rankapproximation technique to significantly reduce the number of measurements. We first benchmarkthe techniques on an existing non-rectangular room model in Finite Element Method simulation withdifferent room settings to validate the high robustness and accuracy of the framework. The evaluationgives accurate results as the reconstructed sound fields are in very good agreement with the simulationreference and the existence of mode shapes are accurately depicted. Finally, we also prove that theframework performs well in cases where the sound field is altered by placing several active low fre-quency absorbers inside the room. This shows that our framework can be further extended to assessthe performance of passive/active absorbers in the domain of room modes equalization

Low frequency sound field reconstruction in a non-rectangular room using a small number of microphones

An accurate knowledge of the sound field distribution inside a room is required to identify and optimally locate corrective measures for room acoustics. However, the spatial recovery of the sound field would result in an impractically high number of microphones in the room. Fortunately, at low frequencies, the possibility to rely on a sparse description of sound fields can help reduce the total number of measurement points without affecting the accuracy of the reconstruction. In this paper, the use of Greedy algorithm and Global curve-fitting techniques are proposed, in order to first recover the modal parameters of the room, and then to reconstruct the entire enclosed sound field at low frequencies, using a reasonably low set of measurements. First, numerical investigations are conducted on a non-rectangular room configuration, with different acoustic properties, in order to analyze various aspects of the reconstruction frameworks such as accuracy and robustness. The model is then validated with an experimental study in an actual reverberation chamber. The study yields promising results in which the enclosed sound field can be faithfully reconstructed using a practically feasible number of microphones, even in complex-shaped and damped rooms

Sound field reconstruction and its application in Room modes equalization

The acoustic quality of a room at low frequencies are heavily dictated by the standing waves phenomenon which inevitably creates discrete eigenmodes in the room. These so-called room modes give rise to imbalances such as coloration and masking effect which can eventually damage the listening experience in the room. Traditional passive absorption methods to dampen these room modes at low frequencies are often either ineffective or bulky. Recently, it has been shown that active absorption system, such as the Electroacoustic Absorber concept, can effectively equalize the modal behavior of a room. However, the setting of its control parameters makes use of simulated room responses through an FEM model rather than actual measurements. In this communication, we cover some advancement in the domain of Sound field reconstruction in a room using Sparse recovery and its applications in Room modes equalization. The ability to accurately reconstruct the spatial responses of the room from a small set of microphone measurements, at first glance, provides a mean to evaluate the performances of both passive and active room absorption devices. Furthermore, with the help of the Sound field reconstruction framework, multiple control parameters of the active Electroacoustic Absorber can be fine-tuned based on actual room information. Finally, prospective future applications are discussed to exploit the full potential of the Sound field reconstruction framework in the domain of Room modes equalization