Alexander Waibel (born 2 May 1956 in Heidelberg, Germany) is a professor of Computer Science at Carnegie Mellon University and Karlsruhe Institute of Technology. Waibel's research interests focus on speech recognition and translation and human communication signals and systems. Waibel is known for the time delay neural network (TDNN), which he developed. It is the first convolutional neural network (CNN) trained by gradient descent, using the backpropagation algorithm. Alex Waibel introduced the TDNN 1987 at ATR in Japan.