An analysis of frequency recognition algorithms and implementation in realtime

Abstract

Frequency recognition is an important task in many engineering fields, such as audio signal processing and telecommunications engineering. There are numerous applications where frequency recognition is absolutely necessary like in Dual-Tone Multi-Frequency (DTMF) detection or the recognition of the carrier frequency of a Global Positioning System (GPS) signal. Furthermore, frequency recognition has entered many other engineering disciplines such as sonar and radar technology, spectral analysis of astronomic data, seismography, acoustics and consumer electronics. Listening to electronic music and playing electronic musical instruments is becoming more and more popular, not only among young musicians. This dissertation details back groundinformation and a preliminary analysis of a musical system, the Generic Musical Instrument System (GMIS), which allows composers to experiment with electronic instruments without actually, learning how to play them.This dissertation gives background information about frequency recognition algorithms implemented in real time. It analyses state-of-the-art techniques, such as Dual- Tone Multiple Frequency (DTMF) implementations and MIDI-based musical systems, in order to work out their similarities. The key idea is to adapt well-proven frequency recognition algorithms of DTMF systems, which are successfully and widely used in telephony. The investigations will show to what extent these principles and algorithms can be applied to a musical system like the GMIS. This dissertation presents results of investigations into frequency recognition algorithms implemented on a Texas Instruments (TI) TMS320C6713 Digital Signal Processor (DSP) core, in order to estimate the frequency of an audio signal in real time. The algorithms are evaluated using selected criteria in terms of speed and accuracy with accomplishing over 9600 single measurements. The evaluations are made with simple sinusoids and musical notes played by instruments as input signals which allows a solid decision, which of these
frequency recognition algorithms is appropriate for audio signal processing and for the constraints of the GMIS in real time.