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[Author] Hiroshi SEKI(3hit)

1-3hit
  • Discriminative Learning of Filterbank Layer within Deep Neural Network Based Speech Recognition for Speaker Adaptation

    Hiroshi SEKI  Kazumasa YAMAMOTO  Tomoyosi AKIBA  Seiichi NAKAGAWA  

     
    PAPER-Speech and Hearing

      Pubricized:
    2018/11/07
      Vol:
    E102-D No:2
      Page(s):
    364-374

    Deep neural networks (DNNs) have achieved significant success in the field of automatic speech recognition. One main advantage of DNNs is automatic feature extraction without human intervention. However, adaptation under limited available data remains a major challenge for DNN-based systems because of their enormous free parameters. In this paper, we propose a filterbank-incorporated DNN that incorporates a filterbank layer that presents the filter shape/center frequency and a DNN-based acoustic model. The filterbank layer and the following networks of the proposed model are trained jointly by exploiting the advantages of the hierarchical feature extraction, while most systems use pre-defined mel-scale filterbank features as input acoustic features to DNNs. Filters in the filterbank layer are parameterized to represent speaker characteristics while minimizing a number of parameters. The optimization of one type of parameters corresponds to the Vocal Tract Length Normalization (VTLN), and another type corresponds to feature-space Maximum Linear Likelihood Regression (fMLLR) and feature-space Discriminative Linear Regression (fDLR). Since the filterbank layer consists of just a few parameters, it is advantageous in adaptation under limited available data. In the experiment, filterbank-incorporated DNNs showed effectiveness in speaker/gender adaptations under limited adaptation data. Experimental results on CSJ task demonstrate that the adaptation of proposed model showed 5.8% word error reduction ratio with 10 utterances against the un-adapted model.

  • A Study on Start-Up Characteristics of Crystal Oscillators Using Resonators with Nonlinear Drive Level Characteristics

    Naoto OHTAKA  Yasuaki WATANABE  Hiroshi SEKIMOTO  

     
    LETTER

      Vol:
    E78-A No:11
      Page(s):
    1528-1530

    This paper describes a simulation technique of start-up characteristics that considers a nonlinearity of the drive level of quartz crystal resonators. A nonlinear resonator model for SPICE where the resonant resistance varies with the voltage added to a resonator is proposed. In an examination using a transistor Colpitts oscillator, the simulation using this technique agreed with the experimental results very well.

  • Algorithms for Multiplexers Assignment after Scheduling and Allocation Steps

    Hiroshi SEKIGAWA  Kiyoshi OGURI  Ryo NOMURA  Yukihiro NAKAMURA  

     
    PAPER

      Vol:
    E75-A No:10
      Page(s):
    1202-1211

    In recent VLSI design of digital data paths, significantly more area is occupied by interconnect elements than by functional units and registers. Nevertheless, until recently most work in data path synthesis has been concentrated on trying to reduce the area of functional units and registers, without paying much attention to the interconnect area. Lately, research that addresses reducing the area of interconnection and of functional units and registers is increasing, but in them, most algorithms for assigning interconnect elements are not efficient enough to optimize the interconnect area. In most current research, algorithms for interconnect element assignment are used to calculate the cost functions during the scheduling and/or allocation steps. This makes it impossible to use efficient optimization algorithms that may consume long time. This paper presents some new algorithms used to assign interconnect elements in data paths. The algorithms minimize the number of multiplexer inputs after the scheduling and operator/register allocations have been made. The algorithms have two characteristics. First, we use a branch and bound method for small problems. We confirmed that exact solutions in practical time can be obtained with this method for rather large problems, when the solutions are restricted to a one-level multiplexer model. Second, we use a certain heuristic method for larger problems. The algorithms have been implemented in C on an Apollo Domain Series 10000.