How many octaves exist the the human range of hearing? Will the same note through all the octaves harmonize?
"How many octaves are there in the human range of hearing?"
The human ear can hear a maximum of 10 octaves: 20-40Hz, 40-80 Hz, 80-160 Hz, 160-320 Hz, 320-640 Hz, 640 Hz to 1.28 KHz, 1.28-2.56 KHz, 2.56-5.12 KHz, 5.12-10.24 KHz, and 10.24 KHz up to the upper edge of the human ability to hear. The next octave would start at 20.48 KHz, which is barely above the high threshold of human hearing.
"Will the same note through all the octaves harmonize?"
To an extent, but you have to be careful. The ear doesn't respond in the same way through the whole range, and typically, neither do instruments. For example, the notes at the bottom of the piano can sound very muddy when playing chords, due to note inharmonicity and the weak fundamentals of the instrument.
Yes, all octaves will harmonize since the wave forms are all complimentary. Human range o pitch perception is 20hz to 20,000hz, which gives about 10 octaves. Below 20hz you’re more likely to just hear them as rhythms. If you include those frequencies you can get about 4 more for a total of 14 octaves.
Given that, basically, a pitch will sound an octave higher when its frequency is doubled, and so on, each C note for instance, will sound like any other C note in a different octave, and won't clash. 'Harmonise' may not be an apposite word.
The range of human voices is approximately 80Hz-255Hz with speech, and up to >2kHz singing, bearing in mind sibilants, harmonics etc. Human hearing, as already noted, is approx. 20Hz - 20kHz, but that varies between individuals. Youngsters range goes a fair bit higher.
The four questions posed here are different. 1 (header). As many as you want. 2. Approx 10 octaves. 3.Basically, yes. 4. There is no definitive answer.