Kernel-interpolation-based spatial active noise control with exterior radiation suppression

A spatial active noise control (ANC) method based on kernel interpolation of a sound field with exterior radiation suppression is proposed. The aim of spatial ANC is to reduce incoming noise over a target region by using multiple secondary sources and microphones. The method based on kernel interpolation of a sound field allows noise attenuation in a regional space with an array of arbitrary geometry. The cost function is defined as the acoustic potential energy, i.e., the regional integral of the power distribution inside the target region. However, this cost function does not take into consideration the exterior radiation of secondary sources. Thus, the acoustic power in the exterior region can be amplified by the output of the secondary sources. We propose two spatial ANC methods with exterior radiation suppression. The first approach is based on the minimization of the cost function formulated as a sum of the interior acoustic potential energy and exterior radiation power. The second approach is based on the minimization of the interior acoustic potential energy with inequality constraints on the exterior radiation power. Adaptive algorithms for minimizing the cost function are derived for the two approaches. Numerical experimental results indicate that the proposed methods can reduce the interior regional noise while suppressing the exterior radiation.Comment: Accepted to International Congress on Acoustics (ICAS) 202

Spatial Active Noise Control Method Based On Sound Field Interpolation From Reference Microphone Signals

A spatial active noise control (ANC) method based on the interpolation of a sound field from reference microphone signals is proposed. In most current spatial ANC methods, a sufficient number of error microphones are required to reduce noise over the target region because the sound field is estimated from error microphone signals. However, in practical applications, it is preferable that the number of error microphones is as small as possible to keep a space in the target region for ANC users. We propose to interpolate the sound field from reference microphones, which are normally placed outside the target region, instead of the error microphones. We derive a fixed filter for spatial noise reduction on the basis of the kernel ridge regression for sound field interpolation. Furthermore, to compensate for estimation errors, we combine the proposed fixed filter with multichannel ANC based on a transition of the control filter using the error microphone signals. Numerical experimental results indicate that regional noise can be sufficiently reduced by the proposed methods even when the number of error microphones is particularly small.Comment: Accepted to International Conference on Acoustics, Speech and Signal Processing (ICASSP) 202

Acute coronary syndrome after liver transplantation in a young primary biliary cholangitis recipient with dyslipidemia: a case report

BACKGROUND: Primary biliary cholangitis (PBC) is a chronic, progressive liver disease associated with dyslipidemia. There is a consensus that PBC does not accelerate coronary artery disease despite high cholesterol levels, so the screening test for the coronary artery is not routinely performed before liver transplantation (LT). To date, no report has described the potential risk of PBC-related dyslipidemia for developing acute coronary syndrome (ACS) after LT. CASE PRESENTATION: A 40-year-old Asian female with a known history of PBC underwent ABO-incompatible living-donor LT, with her husband as the donor. Although she had high cholesterol and triglyceride levels that were refractory to medications, she passed all routine preoperative examinations, including cardiopulmonary function tests and infection screenings. One week after LT, she developed ACS with 90% stenosis of both the left anterior descending artery and left circumflex artery. Emergent stent implantation was successfully performed followed by dual antiplatelet therapy. The long history of PBC and associated severe dyslipidemia for 10 years would have accelerated the atherosclerosis, causing latent stenosis in the coronary artery. Inapparent stenosis might have become apparent due to unstable hemodynamics during the acute phase after LT. CONCLUSIONS: PBC-related dyslipidemia potentially brings a risk for developing ACS after LT. This experience suggests that the preoperative evaluation of the coronary artery should be considered for high-risk patients, especially those who have drug-resistant dyslipidemia