# My first post:

I have found an interesting harmonica here. So, I tried to know more about harmonica.

And, I have read this article , in which the author doesn't mention the physical calculation, which makes a harmonica to be played with a full-octave.

Now, I want to know about the physical calculation in diatonic harmonica. So, my question is: Is there any physical calculation which allow a harmonica can make some different sounds?.

I care about a full-octave only; such as, 8 notes: C6 - D6 - E6 - F6 - G6 - A6 - B6 - B7.

# My second post:

After a short time of waiting, there is an answer for my question. In this answer, there is a function: f=(nv)/(2L). And, he said: "The frequency that is produced in any open tube depends on length".

I don't know the length what is: length of reed, or length of tube; or, both of them. Could you explain it for me, please?

Each tube in the harmonica is an open tube. The frequency that is produced in any open tube depends on length, speed of sound and n, using $f=(nv)/(2L)$. The base note is where n= 1, which is the usual note you hear. If you blow a bit harder, you can hear the first harmonic, where n = 2. Here the frequency is double what was heard earlier (when n=1), and sounds an octave higher. There are more, higher harmonics that can be produced, so the answer is, yes, the physics calculations do predict higher sounds.