sentences:  The limiting factor for telephony based speech recognition is the bandwidth at which speech can be transmitted.For example, a standard land-line telephone only has a bandwidth of 64 kbit/s at a sampling rate of 8 kHz and 8-bits per sample (8000 samples per second * 8-bits per sample = 64000 bit/s).Therefore, for telephony based speech recognition, acoustic models should be trained with 8 kHz/8-bit speech audio files.