Use the above shell script to generate a pd synthesizer, and
drive it either from the Virtual Keyboard or from an external MIDI
keyboard, as described in the Faust intro. Answer the following
- Exploring mistuning:
Since the delay line is not interpolated, the fundamental frequencies
are quantized to frequencies given in Eq.(1), where is the
(integer) delay-line length. This tuning error is very noticeable at
low sampling rates (e.g., 8 kHz or even 22 kHz). However, it is harder
to hear at the standard 48 kHz sampling rate that is standard in AC-97
- At what MIDI key-number do you start to hear the tuning error
when the sampling rate is 44.1 kHz? (MIDI key-number
69 corresponds to A4 at 440 Hz, and key-number 60 is C4 (``middle
Hz.) If possible,
determine the first ``out of tune'' key-number when the sampling
rate is 8 KHz.
- Repeat the previous problem using fdelay in place of
delay, and explain why your results make sense.
- Measure the final signal value for three different notes after
sound is no longer audible.
- Explain why the signal usually does not decay to zero.
- What final values are possible?
- What property of the excitation noise burst can guarantee that
the signal will decay to zero?