Comparative analysis of methods used in the design of DTMF tone detectors

Dual-Tone Multi-Frequency (DTMF) Signals are used in touch-tone telephones as well as many other areas. Since analog devices are rapidly being replaced with digital devices, digital DTMF decoders with superior quality have become the ideal replacement. In this paper a comparative analysis on the four DTMF detector designs are studied. They are namely, filter design approach, Discrete Fourier Transform(DFT), Goertzel Algorithm and Sub-Band Non-Uniform DFT (SB-NDFT). The algorithms are developed in the MatLab environment and the implementation is done on a Digital Signal Processor, TMS320 C6713.The figure of merit and computational complexity are used as a performance measure and in both cases the SB-NDFT is found to be the best.