Added README to Goertzel

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+# Goertzel
+Scriptable tone detection and audio analysis
+
+## Contents
+
+* **goertzel.c**
+  * Does all the dirty work using Goertzel algorithm
+  * http://en.wikipedia.org/wiki/Goertzel_algorithm
+  * Detect specified tones and print their levels
+  * Filter tones using tresholds
+     * Eg.: Print levels only when treshold is crossed (=event detection)
+  * TODO
+     * treshold hysteresis
+
+* Sample scripts using goertzel.c
+  * **dtmf.sh**: decodes DTMF signals in audio
+  * **histogram.pl**: shows goertzel output in ASCII graphs
+  * **histogram.sh**: example using histogram.pl to draw realtime equalizer
+  * **sleepmon.sh**: Generates frequency on soundcard output and detects it on input
+     * Can be used to detect and log motion using soundcard and PIR sensor or NC switch
+  * TODO
+     * Guitar tuner
+     * Send me more...