Search

On dokuzuncu yüzyılın bilim ve teknik alanındaki başlıca icatlarından biri telefondur. 1875’teki icadından sonra dünya ülkelerine hızla yayılmıştır. Osmanlılar, patenti Alexander Graham Bell tarafından 1876’de alınan telefon ile II. Abdülhamid döneminde, 1881’de tanışmıştır. Ancak telefonla ilk deneyimleri çok kısa sürmüştür: Telefon, “gizli-saklı” işlerde kullanılma ihtimali üzerine, 1886’da yasaklanmıştır. Avrupa’dan Osmanlı liman kentlerine gelen telefonlar gümrüklerde “tevkif edilerek” muhafaza altına alınmıştır. Bu tedbirlere rağmen telefonun kaçak yollarla ülkeye girişi engellenememiş ve zaman içerisinde kullanımına yönelik talepler artmıştır. II. Meşrutiyet’in liberal politikaları çerçevesinde yabancı şirketlere imtiyaz verilerek telefon kullanımı teşvik edilmiştir. İstanbul, telefon ile özdeşleşen başlıca Osmanlı kenti olmuştur. İzmir ve Aydın gibi ticaret kentleri ile Anadolu’nun muhtelif yerlerindeki kullanımı sınırlı kalmıştır. Telefonun Osmanlı’ya ilk girişinden serbest bırakılmasına kadar geçen sürede, popüler süreli yayınlarda telefona dair geniş bir literatür oluşmuştur. Bu süre içerisinde, telefon kullanımı konusunda gelişmiş ülkelere nazaran oldukça geri kalan Osmanlı’nın telefonla imtihanı yoğun bürokratik yazışmalarda da kendini göstermiştir. An important technological advance of the nineteenth century, the telephone, spread throughout the world following its invention in 1875. Patented by Alexander Graham Bell in 1876, it was introduced in the Ottoman Empire in 1881 during Abdulhamid II’s reign. The Ottomans’ experience with the device was rather short: It was prohibited because of possible clandestine uses. Devices arriving in Ottoman harbours were seized and stored. However, the illegal import of the telephones could not be prevented because of increasing demands. The liberalistic policies of the Second Constitution that extended privileges to foreign companies, encouraged its use. Istanbul had the largest telephone network but its use was limited in İzmir, Aydın and other Anatolian cities. From its introduction to its free use in 1908, a large amount of literature appeared in popular periodicals. Telephone-related issues were discussed in many bureaucratic documents which witnessed its delayed adoption in the Empire, compared to developed countries of the time.

In recent years, there have been significant advances in communication technology, but speech signals still suffer from low perceived quality caused by bandwidth limitations of telephone networks. The bandwidth extension (BWE) approach adds high-frequency components of the speech signal to band-limited telephone speech and increases speech perception significantly. In this work, we develop a new method for representation of vocal tract filter coefficients using log of filter bank energy (LFBE) parameters as an alternative for mel-frequency cepstral coefficients (MFCCs). This approach is based on a strong correlation between the spectral components of low- and high-band spectrums. Furthermore, the performances of Gaussian mixture model and multilayer perceptron neural network methods for estimation of the high-frequency envelope are evaluated. Objective evaluations of the obtained results indicate that the LFBE feature vectors have better performance than the MFCCs. In addition, findings of the objective evaluations showed that using a neural network, which is not common in BWE, achieves a better performance as compared to the Gaussian mixture model.