An echo canceler function part 28 is composed of hardware and an adaptive filter based upon its NLMSalgorithm is so constituted that its filter coefficient ω is found by performing normalization processing by previously computing the reciprocal number (1/A) of a square norm regarding a vector series of an output sound signal and performing multiplication by the reciprocal number as to each tap of the filter. エコーキャンセラ機能部28をハードウエアで構成し、そのNLMSアルゴリズムに基づく適応フィルタを、出力音響信号のベクトル系列に関する2乗ノルムの逆数(1/A)を予め演算し、フィルタの各タップについて前記逆数を乗じることで正規化処理を行い、フィルタ係数ωを求めるように構成する。 - 特許庁