- Joined Aug 5, 2011
How about this:The high pass filter is optional but you should still use it, but for a reliable ADC you must have a low pass filter, preferably pretty steep, cutting anything above Fs/2.
Mic ---> Hardware filter ---> ADC ---> Digital filter ---> Control section ---> Leds
In the above, hardware filter: high pass filter + Low pass filter to limit the frequency input between ~150Hz and ~2000Hz
ADC, sample at 4Khz
Digital filters, used to subdivide frequency spectrum into several sub-intervals for analysis of specific frequency spectrum of word being spoken...
But how does the number of digital filters influence on the result?
Control section, basically find/compute the fingerprint of sample word spoken...then perform some kind of comparison with stored words in the dictionary (memory)...
As for the method of recognition, I have explained a bit above but basicaly I can use euclidean distance to find the fingerprint that is closest match...You still didn´t say what method of recognition youre using.
Either your method will be so good that it can keep running all the time and take care of this problem by itself in a way that it doesn´t produce false positives, or you will have to set up a thing known as Noise gate.
This monitors the input signal and when it reaches some level the gate opens and passes the signal to the next stage. When the signal drops below the threshold, the gate waits for some time and if the signal didn´t get above the threshold again, it closes and stops passing the signal. Offcourse it is easier to do this in software rather than in hardware.
(by level I mean absolute voltage wrt the resting level)
Or use a correlation of the two fingerprints...
Well I'm still reading and doing reseachs as I only have vague ideas...not a very clear picture yet...
But I'm very interrested in your method about Noise gate...threshold...where does it fit in my block diagram?
Thanks so much!