I am looking for a way to detect the presence of a single musical note that lies within a real-world audio signal. For example, from a piano recording, I want to detect when Middle C (440 hz) is sounded while ignoring all the other notes.
Perhaps some kind of tunable bandpass filter would do the job? If so, it would have to be a very narrow bandpass filter because musical notes are separated in frequency by a ratio of about 1.06, which is quite close.
The thing might also be thought of as an AM receiver that operates with a carrier frequency not in the RF but in the audio frequency range.
In my application, the centre (detected) frequency will be controlled by microprocessor. The receiver will frequency-hop, quickly changing the detection frequency. I am imagining that the microprocessor might do this by supplying a clock frequency or by directly writing a digital value.
It does not need to be a precision circuit — simplicity and low cost are more important. The application can tolerate a fair degree of error.
Any ideas?
Thank-you!
Gordon Hicks
