Active Noise Control in The New Century: The Role and Prospect of Signal Processing

Since Paul Leug's 1933 patent application for a system for the active control of sound, the field of active noise control (ANC) has not flourished until the advent of digital signal processors forty years ago. Early theoretical advancements in digital signal processing and processors laid the groundwork for the phenomenal growth of the field, particularly over the past quarter-century. The widespread commercial success of ANC in aircraft cabins, automobile cabins, and headsets demonstrates the immeasurable public health and economic benefits of ANC. This article continues where Elliott and Nelson's 1993 Signal Processing Magazine article and Elliott's 1997 50th anniversary commentary~\cite{kahrs1997past} on ANC left off, tracing the technical developments and applications in ANC spurred by the seminal texts of Nelson and Elliott (1991), Kuo and Morgan (1996), Hansen and Snyder (1996), and Elliott (2001) since the turn of the century. This article focuses on technical developments pertaining to real-world implementations, such as improving algorithmic convergence, reducing system latency, and extending control to non-stationary and/or broadband noise, as well as the commercial transition challenges from analog to digital ANC systems. Finally, open issues and the future of ANC in the era of artificial intelligence are discussed.Comment: Inter-Noise 202

Do uHear? Validation of uHear App for Preliminary Screening of Hearing Ability in Soundscape Studies

Studies involving soundscape perception often exclude participants with hearing loss to prevent impaired perception from affecting experimental results. Participants are typically screened with pure tone audiometry, the "gold standard" for identifying and quantifying hearing loss at specific frequencies, and excluded if a study-dependent threshold is not met. However, procuring professional audiometric equipment for soundscape studies may be cost-ineffective, and manually performing audiometric tests is labour-intensive. Moreover, testing requirements for soundscape studies may not require sensitivities and specificities as high as that in a medical diagnosis setting. Hence, in this study, we investigate the effectiveness of the uHear app, an iOS application, as an affordable and automatic alternative to a conventional audiometer in screening participants for hearing loss for the purpose of soundscape studies or listening tests in general. Based on audiometric comparisons with the audiometer of 163 participants, the uHear app was found to have high precision (98.04%) when using the World Health Organization (WHO) grading scheme for assessing normal hearing. Precision is further improved (98.69%) when all frequencies assessed with the uHear app is considered in the grading, which lends further support to this cost-effective, automated alternative to screen for normal hearing.Comment: Full paper submitted to 24th International Congress on Acoustic

Assessment of a cost-effective headphone calibration procedure for soundscape evaluations

To increase the availability and adoption of the soundscape standard, a low-cost calibration procedure for reproduction of audio stimuli over headphones was proposed as part of the global ``Soundscape Attributes Translation Project'' (SATP) for validating ISO/TS~12913-2:2018 perceived affective quality (PAQ) attribute translations. A previous preliminary study revealed significant deviations from the intended equivalent continuous A-weighted sound pressure levels ($L_{\text{A,eq}}$) using the open-circuit voltage (OCV) calibration procedure. For a more holistic human-centric perspective, the OCV method is further investigated here in terms of psychoacoustic parameters, including relevant exceedance levels to account for temporal effects on the same 27 stimuli from the SATP. Moreover, a within-subjects experiment with 36 participants was conducted to examine the effects of OCV calibration on the PAQ attributes in ISO/TS~12913-2:2018. Bland-Altman analysis of the objective indicators revealed large biases in the OCV method across all weighted sound level and loudness indicators; and roughness indicators at \SI{5}{\%} and \SI{10}{\%} exceedance levels. Significant perceptual differences due to the OCV method were observed in about \SI{20}{\%} of the stimuli, which did not correspond clearly with the biased acoustic indicators. A cautioned interpretation of the objective and perceptual differences due to small and unpaired samples nevertheless provide grounds for further investigation.Comment: For 24th International Congress on Acoustic

Preliminary investigation of the short-term in situ performance of an automatic masker selection system

Soundscape augmentation or "masking" introduces wanted sounds into the acoustic environment to improve acoustic comfort. Usually, the masker selection and playback strategies are either arbitrary or based on simple rules (e.g. -3 dBA), which may lead to sub-optimal increment or even reduction in acoustic comfort for dynamic acoustic environments. To reduce ambiguity in the selection of maskers, an automatic masker selection system (AMSS) was recently developed. The AMSS uses a deep-learning model trained on a large-scale dataset of subjective responses to maximize the derived ISO pleasantness (ISO 12913-2). Hence, this study investigates the short-term in situ performance of the AMSS implemented in a gazebo in an urban park. Firstly, the predicted ISO pleasantness from the AMSS is evaluated in comparison to the in situ subjective evaluation scores. Secondly, the effect of various masker selection schemes on the perceived affective quality and appropriateness would be evaluated. In total, each participant evaluated 6 conditions: (1) ambient environment with no maskers; (2) AMSS; (3) bird and (4) water masker from prior art; (5) random selection from same pool of maskers used to train the AMSS; and (6) selection of best-performing maskers based on the analysis of the dataset used to train the AMSS.Comment: paper submitted to the 52nd International Congress and Exposition on Noise Control Engineering held in Chiba, Greater Tokyo, Japan, on 20-23 August 2023 (Inter-Noise 2023

Crossing the Linguistic Causeway: Ethnonational Differences on Soundscape Attributes in Bahasa Melayu

Despite being neighbouring countries and sharing the language of Bahasa Melayu (ISO 639-3:ZSM), cultural and language education policy differences between Singapore and Malaysia led to differences in the translation of the "annoying" perceived affective quality (PAQ) attribute from English (ISO 639-3:ENG) to ZSM. This study expands upon the translation of the PAQ attributes from eng to ZSM in Stage 1 of the Soundscapes Attributes Translation Project (SATP) initiative, and presents the findings of Stage 2 listening tests that investigated ethnonational differences in the translated ZSM PAQ attributes and explored their circumplexity. A cross-cultural listening test was conducted with 100 ZSM speakers from Malaysia and Singapore using the common SATP protocol. The analysis revealed that Malaysian participants from non-native ethnicities (my:o) showed PAQ perceptions more similar to Singapore (sg) participants than native ethnic Malays (MY:M) in Malaysia. Differences between Singapore and Malaysian groups were primarily observed in stimuli related to water features, reflecting cultural and geographical variations. Besides variations in water source-dominant stimuli perception, disparities between MY:M and SG could be mainly attributed to vibrant scores. The findings also suggest that the adoption of region-specific translations, such as membingitkan in Singapore and menjengkelkan in Malaysia, adequately addressed differences in the annoying attribute, as significant differences were observed in one or fewer stimuli across ethnonational groups The circumplexity analysis indicated that the quasi-circumplex model better fit the data compared to the assumed equal angle quasi-circumplex model in ISO/TS 12913-3, although deviations were observed possibly due to respondents' unfamiliarity with the United Kingdom-centric context of the stimulus dataset...Comment: Preprint submitted to Elsevier for revie

Exploratory Assessment of K-means Clustering to Classify 18F-Flutemetamol Brain PET as Positive or Negative

Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.Rationale: We evaluated K-means clustering to classify amyloid brain PETs as positive or negative. Patients and Methods: Sixty-six participants (31 men, 35 women; age range, 52–81 years) were recruited through a multicenter observational study: 19 cognitively normal, 25 mild cognitive impairment, and 22 demen- tia (11 Alzheimer disease, 3 subcortical vascular cognitive impairment, and 8 Parkinson–Lewy Body spectrum disorder). As part of the neurocognitive and imaging evaluation, each participant had an 18F-flutemetamol (Vizamyl, GE Healthcare) brain PET. All studies were processed using Cortex ID soft- ware (General Electric Company, Boston, MA) to calculate SUV ratios in 19 regions of interest and clinically interpreted by 2 dual-certified radiologists/ nuclear medicine physicians, using MIM software (MIM Software Inc, Cleveland, OH), blinded to the quantitative analysis, with final interpreta- tion based on consensus. K-means clustering was retrospectively used to classify the studies from the quantitative data. Results: Based on clinical interpretation, 46 brain PETs were negative and 20 were positive for amyloid deposition. Of 19 cognitively normal partici- pants, 1 (5%) had a positive 18F-flutemetamol brain PET. Of 25 participants with mild cognitive impairment, 9 (36%) had a positive 18F-flutemetamol brain PET. Of 22 participants with dementia, 10 (45%) had a positive 18F-flutemetamol brain PET; 7 of 11 participants with Alzheimer disease (64%), 1 of 3 participants with vascular cognitive impairment (33%), and 2 of 8 participants with Parkinson–Lewy Body spectrum disorder (25%) had a positive 18F-flutemetamol brain PET. Using clinical interpretation as the criterion standard, K-means clustering (K = 2) gave sensitivity of 95%, specificity of 98%, and accuracy of 97%. Conclusions: K-means clustering may be a powerful algorithm for classifying amyloid brain PET.This is a multisite project of the Toronto Dementia Research Alli- ance (www.tdra.utoronto.ca) partly funded by Brain Canada, The Edward Foundation, the Canadian Institutes of Health Research (FDN 159910), the LC Campbell Cognitive Neurology Research Unit, Sunnybrook Research Institute, and the Dr Sandra Black Cen- tre for Brain Resilience and Recovery. M.F. received support from the Saul A. Silverman Family Foundation as a Canada Interna- tional Scientific Exchange Program and the Morris Kerzner Memo- rial Fund. We gratefully acknowledge GE Healthcare and the CAMH Brain Health Imaging Centre for manufacturing and sup- plying the ligand. We are also grateful to GE Healthcare for provid- ing the software to calculate the brain region of interest SUV ratios. The study protocol, Brain Eye Amyloid Memory study (BEAM), is registered at https://clinicaltrials.gov/ct2/show/NCT02524405? term=beam+sandra+black&rank=1

Soundscape assessment : towards a validated translation of perceptual attributes in different languages

The recently published ISO/TS 12913-2:2018 standard aims to provide researchers and practitioners around the world with a reliable questionnaire for soundscape characterization. The ISO Technical Specifications report protocols and attributes grounded in the soundscape literature, but only includes an English version. The applicability and reliability of these attributes in non-English speaking regions remains an open question, as research investigating translations of soundscape attributes is limited. To address this gap, an international collaboration was initiated with soundscape researchers from all over the world. Translation into 15 different languages, obtained through focus groups and panels of experts in soundscape studies, are proposed. The main challenges and outcomes of this preliminary exercise are discussed. The long-term objective is to validate the proposed translations using standardized listening experiments in different languages and geographical regions as a way to promote a widespread use of the soundscape attributes, both in academia and practice, across locations, populations and languages

Sulforaphane-enriched extracts from glucoraphanin-rich broccoli exert antimicrobial activity against gut pathogens in vitro and innovative cooking methods increase in vivo intestinal delivery of sulforaphane

Purpose Studies on broccoli (Brassica oleracea var. italica) indicate beneficial effects against a range of chronic diseases, commonly attributed to their bioactive phytochemicals. Sulforaphane, the bioactive form of glucoraphanin, is formed by the action of the indigenous enzyme myrosinase. This study explored the role that digestion and cooking practices play in bioactivity and bioavailability, especially the rarely considered dose delivered to the colon. Methods The antimicrobial activity of sulforaphane extracts from raw, cooked super broccoli and cooked super broccoli plus mustard seeds (as a source myrosinase) was assessed. The persistence of broccoli phytochemicals in the upper gastrointestinal tract was analysed in the ileal fluid of 11 ileostomates fed, in a cross-over design, super broccoli soup prepared with and without mustard seeds. Results The raw super broccoli had no antimicrobial activity, except against Bacillus cereus, but cooked super broccoli (with and without mustard seeds) showed considerable antimicrobial activity against various tested pathogens. The recovery of sulforaphane in ileal fluids post soup consumption was < 1% but addition of mustard seeds increased colon-available sulforaphane 6-fold. However, when sulforaphane was extracted from the ileal fluid with the highest sulforaphane content and tested against Escherichia coli K12, no inhibitory effects were observed. Analysis of glucosinolates composition in ileal fluids revealed noticeable inter-individual differences, with six “responding” participants showing increases in glucosinolates after broccoli soup consumption. Conclusions Sulforaphane-rich broccoli extracts caused potent antimicrobial effects in vitro, and the consumption of sulforaphane-enriched broccoli soup may inhibit bacterial growth in the stomach and upper small intestine, but not in the terminal ileum or the colon

Active control of noise through open windows

Active noise control (ANC) is a noise abatement technique that preserves an abode’s natural ventilation when applied on domestic windows. ANC systems for open windows mitigates noise at the receivers’ end, which augments solutions that are less effective for urban noise in high-rise cities. The target of the ANC system is to reduce noise that propagates through an open aperture, such as a window, into the interior of a room. This thesis presents a systematic approach to the open window ANC system design to address the complex practical implementation challenges. Firstly, the fundamental limits of the ANC system in controlling noise through an open aperture are determined by numerical simulations. The investigation into the performance of different physical arrangements reveals that the upper limit frequency limit of control is determined by the separation distance between the sources of the planar array, distributed evenly in the aperture. As a result, the minimum number of sources needed for good control is generalized for a rectangular aperture and the dominant noise incidence angles. Based on the design guidelines for the open aperture, a further numerical study was conducted to investigate the influence of passive elements (i.e. glass panel) in the aperture on the active control performance. Moreover, it was shown that the arrangement of control sources in a partially glazed aperture (~75%) based on the established design guidelines could provide more attenuation than a fully-glazed aperture without active control. Next, an experimental setup with a full-sized domestic window is designed and installed on a room model placed in a recording studio. The active control units were custom designed and secured within the aperture via the security grille. A total of 24 control sources of the multiple-input-multiple-output (MIMO) ANC system are implemented on a fully-opened two-panel sliding window. The active control attenuation performance was predicted to be 10 dB at the error microphones through offline simulations with measured transfer functions. Due to the high computational complexity, the real-time active control system was implemented on an FPGA platform, which operated at 25 kHz sampling rate. The active control performance was determined by an array of 18 microphones distributed within the interior of the test chamber, of which 12 microphones monitored the noise directly in front of the aperture in a plane array, and the rest were distributed according to the ISO standard to measure the energy-averaged sound pressure level of the room interior. The active control performance was compared to the passive insulation provided by a fully-closed window. In both tonal and broadband noise scenarios, the active control system was comparable to the passive insulation of a fully-glazed window in the mid-frequencies and at oblique angles of incidence for the entire frequency range of interest. Lastly, considerations to increase the practicability of the active noise control system for domestic windows are discussed. Namely, the omission of error microphones but implementing fixed filters and the reduction of the number of control sources that are distributed in the aperture in an effort to reduce the physical and visual obstructions.Doctor of Philosoph

Regularisation of the equivalent source method for robust numerical modelling of acoustic scattering

The equivalent source method can be used to model acoustic scattering, by representing the scattering object with a set of equivalent sources that satisfy a boundary condition. The equivalent source strengths are optimised by a least-squares method. When the equivalent sources are positioned further from the boundary to reduce the boundary condition error, the optimisation becomes ill-conditioned. This limits the application of the equivalent source method in irregularly-shaped objects as boundary condition error is highly sensitive to equivalent source placement. To overcome the problem of ill-conditioning, a regularisation parameter is introduced, which increases the robustness to errors in the modelled acoustic field by limiting the power of overdriven equivalent sources. Simulations of a rigid infinite wall with an equivalent dipole line-array, reveal that regularisation reduces boundary condition error in all ill-conditioned cases. Good trade-offs between boundary condition error and regularisation are achieved for a wide range of regularisation parameter values. This allows the results to be calculated for varying frequencies and distances between the equivalent sources and the boundary. Regularisation reduces the sensitivity of boundary condition error to equivalent source placement, thereby increasing the flexibility of the equivalent source method for irregularly-shaped scattering object