Dar Bantlı Konuşma İzgel Zarfının Sinir Ağları Kullanılarak Genişletilmesi ve Kalitesinin Artırılması

Geleneksel telefon sistemlerinde, 7−8 kHz’e kadar bileşenleri olan insan sesi 3.4 kHz bant genişliğine sahip bir alçak geçirgen süzgeçten geçirilip 8 kHz’te örneklenerek gönderilir. Kodlama ve benzeri işlemlerden kaynaklanan hiçbir kayıp olmasa bile, yüksek frekans bölgesinin süzülerek kaybolmasından kaynaklanan bir kalite kaybı söz konusudur. Bu kayıp, anlaşılabilirliği pek etkilememekle beraber konuşma kalitesinde hissedilir bir bozulmaya yol açmaktadır. Bu çalışmada, izgel zarfın düşük frekanslı bölgelerinden faydalanılarak; süzülen yüksek frekanslı bölgelerin izgel zarfı elde edilmeye çalışılmış ve izgel zarfın genişletilmesi olarak da nitelenebilecek bu işlem için yapay sinir ağları yöntemi kullanılmıştır. Daha sonra genişletilen bu izgel zarf kullanılarak kaybolan yüksek frekanslı bölgeler kaynak-süzgeç modeliyle yeniden oluşturulmuş ve böylece konuşma kalitesini artırılması hedeflenmiştir. Geliştirilen bu yöntem telefon kalitesindeki konuşmalar için kullanılmakla birlikte, daha düşük bant genişliğine sahip konuşmalar (1.8 kHz) için de kullanılabilir.

Anahtar Kelimeler:

İzgel zarf genişletme, İzgel zarf dışdeğerleme, konuşma kalitesi iyileştirme, sinir ağları

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