Psycho-acoustics... Effectively we have been trained by experience that harmonic overtones are just that, and the fundamental is the root note. One pretty interesting example of this phenomenon is how tympani drums make perceived notes lower than their physical size would support. The tympani makes two closely spaced resonant notes (due to the physics of their closed curved back chamber), and our brain interprets the two pitches as both being overtones of a missing lower fundamental (equal to the difference between the two real pitches present). So we hear a lower pitch that isn't really there. In LF loudspeakers we can sometimes get distortion products louder than the fundamentals, when those fundamentals are well below the output capability of the speaker/box. JR
So I'm guessing that this must be something both measurable and predictable? Are these principals the basis for sub-harmonic synthesis?
Let's consider a sound with a strong output at 100 Hz. Is this a fundamental or an overtone?Fundamental = 100, 1st harmonic = 200, 2nd = 300, 3rd = 400Fundamental = 50, 1st harmonic = 100, 2nd = 150, 3rd = 200Fundamental = 25, 1st harmonic = 50, 2nd = 75, 3rd = 100The brain integrates the missing fundamental since the information regarding the pitch is present in the harmonic structure of the waveform. Most bass rigs cannot produce adequate output at 31 Hz, the fundamental for the B string on a 5 string bass. Yet, one can easily distinguish this low B from the B played an octave higher because of this processing in our brain. I won't even get into the typical bookshelf or computer speaker, but it is possible to "hear" the low B played even if the 1st harmonic is missing if so long as the rest of the harmonics are audible.I am not aware if existing subharmonic generators are based on this principle. I think they just add in a waveform an octave below the most prominent low frequency. Indeed, if the name is correct, then they should be synthesizing sub-harmonics (e.g. 1/n, where n=the 1st, 2nd, 3rd etc. subharmonic).
So if I was to simultaneously generate 4 sine waves at 400Hz, 475Hz, 550Hz & 625Hz would we perceive the pitch to be 75Hz?The intervals between the frequencies are the same as the harmonics for a 75Hz fundamental but occur at frequencies that are 25Hz out from the order of those harmonics.
Can a harmonic be produced that is lower than the perceived pitch (fundamental)?
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