Individual fine tuning of single microphone noise reduction settings in hearing aids

Listening in environments with different kinds of background noises is especially difficult for individuals who suffer from hearing loss. For this reason, most modern hearing aids contain noise reduction (NR) algorithms. It is known that individual preferences for the settings of these algorithms are very diverse. Therefore, research is conducted to find NR parameters that are important for determining the preference of a listener and to find out what aspects, other than speech intelligibility, influence this preference. An important theme in this work is the trade-off between noise attenuation and signal quality which is a delicate balance that presumably determines the success of individual fine tuning of NR settings. When removing more unwanted noise from a signal the signal quality is inevitably affected as signal distortions arise. In the first four chapters of this thesis we investigated the effect of NR on listening effort, and the effect of varying NR time constants and NR strength on listener preference. The individual trade-off was a supposed reason as to why preferences are so diverse. In the fifth chapter of this thesis we visualized this trade-off and indeed found that each individual has a different tolerance towards background noise and signal distortions. The main aim of this thesis was to aid in the adequate and efficient selection and fine tuning of the optimal NR algorithm in a hearing aid for each individual listener. All research chapters of this work have contributed to this overarching goal

Numerical simulations of the full ink-jet printing processes: From jetting to evaporation

Ink-jet printing requires to perfectly control both the jetting of droplets and the subsequent droplet evaporation and absorption dynamics. Considerable complexity arises due to the fact that ink is constituted of a mixture of different liquids, surfactants and pigments. Using a sharp-interface ALE finite element method, we numerically investigate the main aspects of ink-jet printing, both on the jetting side and on the drying side. We show how a short pause in jetting can result in clogged nozzles due to solvent evaporation and discuss approaches how to prevent this undesired phenomenon. Once the droplets have been jetted on paper and is evaporating, the print quality can be deteriorated by the well-known coffee-stain effect, i.e. the preferential deposition of particles near the rim of the droplet. This can be prevented in several ways, e.g. employing controlled Marangoni flow via surfactants or co-solvents or printing on a primer layer jetted in beforehand, thus creating a homogeneous deposition pattern for a perfect final printout

Infrared imaging and acoustic sizing of a bubble inside a MEMS piezo ink channel

Piezo drop-on-demand inkjet printers are used in an increasing number of applications because of their reliable deposition of droplets onto a substrate. Droplets of a few picoliters are ejected from an inkjet nozzle at frequencies of up to 100 kHz. However, the entrapment of an air microbubble in the ink channel can severely impede the productivity and reliability of the printing system. The air bubble disturbs the channel acoustics, resulting in disrupted drop formation or failure of the jetting process. Here we study a micro-electro-mechanical systems-based printhead. By using the actuating piezo transducer in receive mode, the acoustical field inside the channel was monitored, clearly identifying the presence of an air microbubble inside the channel during failure of the jetting process. The infrared visualization technique allowed for the accurate sizing of the bubble, including its dynamics, inside the intact printhead. A model was developed to calculate the mutual interaction between the channel acoustics and the bubble dynamics. The model was validated by simultaneous acoustical and infrared detection of the bubble. The model can predict the presence and size of entrapped air bubbles inside an operating ink channel purely from the acoustic response

Sticky bubbles

We discuss the physical forces that are required to remove an air bubble immersed in a liquid from a corner. This is relevant for inkjet printing technology, as the presence of air bubbles in the channels of a printhead perturbs the jetting of droplets. A simple strategy to remove the bubble is to ush the ink past the bubble by providing a high pressure pulse. In this report we rst compute the viscous drag forces that such a ow exerts on the bubble. Then, we compare this to the \sticking forces" on the bubble, due to the capillary interaction with the wall. From this we can estimate the required ow velocities for bubble removal, as a function of channel geometry, contact angle and ink properties. Finally, we investigate other ways to exert a force on a trapped bubble. In particular we focus on forces induced by electric elds which can alter the contact angle of the drop, or by locally applying thermal gradients. Once again, these forces are compared to the sticking forces to identify the parameters where the bubble can be removed

Hepatocellular adenoma in men:A nationwide assessment of pathology and correlation with clinical course

BACKGROUND & AIMS: Hepatocellular adenomas (HCA) rarely occur in males, and if so, are frequently associated with malignant transformation. Guidelines are based on small numbers of patients and advise resection of HCA in male patients, irrespective of size or subtype. This nationwide retrospective cohort study is the largest series of HCA in men correlating (immuno)histopathological and molecular findings with the clinical course. METHODS: Dutch male patients with available histological slides with a (differential) diagnosis of HCA between 2000 and 2017 were identified through the Dutch Pathology Registry (PALGA). Histopathology and immunohistochemistry according to international guidelines were revised by two expert hepatopathologists. Next generation sequencing (NGS) was performed to confirm hepatocellular carcinoma (HCC) and/or subtype HCA. Final pathological diagnosis was correlated with recurrence, metastasis and death. RESULTS: A total of 66 patients from 26 centres fulfilling the inclusion criteria with a mean (±SD) age of 45.0 ± 21.6 years were included. The diagnosis was changed after expert revision and NGS in 33 of the 66 patients (50%). After a median follow‐up of 9.6 years, tumour‐related mortality of patients with accessible clinical data was 1/18 (5.6%) in HCA, 5/14 (35.7%) in uncertain HCA/HCC and 4/9 (44.4%) in the HCC groups (P = .031). Four B‐catenin mutated HCA were identified using NGS, which were not yet identified by immunohistochemistry and expert revision. CONCLUSIONS: Expert revision with relevant immunohistochemistry may help the challenging but prognostically relevant distinction between HCA and well‐differentiated HCC in male patients. NGS may be more important to subtype HCA than indicated in present guidelines