A Retinex-based Image Enhancement Scheme with Noise Aware Shadow-up Function

This paper proposes a novel image contrast enhancement method based on both a noise aware shadow-up function and Retinex (retina and cortex) decomposition. Under low light conditions, images taken by digital cameras have low contrast in dark or bright regions. This is due to a limited dynamic range that imaging sensors have. For this reason, various contrast enhancement methods have been proposed. Our proposed method can enhance the contrast of images without not only over-enhancement but also noise amplification. In the proposed method, an image is decomposed into illumination layer and reflectance layer based on the retinex theory, and lightness information of the illumination layer is adjusted. A shadow-up function is used for preventing over-enhancement. The proposed mapping function, designed by using a noise aware histogram, allows not only to enhance contrast of dark region, but also to avoid amplifying noise, even under strong noise environments.Comment: To appear in IWAIT-IFMIA 201

A privacy-preserving method using secret key for convolutional neural network-based speech classification

In this paper, we propose a privacy-preserving method with a secret key for convolutional neural network (CNN)-based speech classification tasks. Recently, many methods related to privacy preservation have been developed in image classification research fields. In contrast, in speech classification research fields, little research has considered these risks. To promote research on privacy preservation for speech classification, we provide an encryption method with a secret key in CNN-based speech classification systems. The encryption method is based on a random matrix with an invertible inverse. The encrypted speech data with a correct key can be accepted by a model with an encrypted kernel generated using an inverse matrix of a random matrix. Whereas the encrypted speech data is strongly distorted, the classification tasks can be correctly performed when a correct key is provided. Additionally, in this paper, we evaluate the difficulty of reconstructing the original information from the encrypted spectrograms and waveforms. In our experiments, the proposed encryption methods are performed in automatic speech recognition~(ASR) and automatic speaker verification~(ASV) tasks. The results show that the encrypted data can be used completely the same as the original data when a correct secret key is provided in the transformer-based ASR and x-vector-based ASV with self-supervised front-end systems. The robustness of the encrypted data against reconstruction attacks is also illustrated.Comment: To appear in the 31st European Signal Processing Conference (EUSIPCO 2023

第二外国語としてのスペイン語の教科書分析 : コミュニケーション能力の4観点から

「コミュニケーション」を目標に作成され、広く大学で使われている、第二外国語としてのスペイン語の教科書『スペイン語とわたし』（廣康・モレノ・モジャノ・ビバンコス，2013）を、Canale and Swain (1980)およびCanale (1983)で提唱されたコミュニケーション能力の4つの構成要素である「文法能力」、「社会言語学的能力」、「談話能力」、「方略能力」の観点から分析し、その目的に合う教授法を導くべく考察した。その結果、上記4観点についてすべてを含んでいることが明らかとなった。しかしながら、「文法能力」以外の育成については、教科書のどの活動がどの能力育成につながるかを授業者が読み取る必要がある。また、それをもとに、スペイン語の授業における言語活動をおこなう際には、コミュニケーションの目的や使用場面などに意識を向けるよう学習者に働きかけることも、授業者の役割として求められる

複数のパラメータ共有構造を用いた音響モデリング

Open House, ISM in Tachikawa, 2013.6.14統計数理研究所オープンハウス（立川）、H25.6.14ポスター発