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Author Topic: Harmonics and fundamentals  (Read 8122 times)

luis Markson

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Re: Harmonics and fundamentals
« Reply #10 on: April 30, 2011, 07:01:42 am »

  Sure... a subharmonic

  Hammer

I was under the impression that "subharmonic" meant a perceived pitch below a series of synthesised harmonics.
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Charlie Zureki

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Re: Harmonics and fundamentals
« Reply #11 on: April 30, 2011, 07:49:22 am »

  Sure... a subharmonic

  Hammer

I was under the impression that "subharmonic" meant a perceived pitch below a series of synthesised harmonics.

  Hello Luis,

   In regards to one of your previous posts .... A perceived pitch and a fundimental can be be the same, or, two separate things. (reread JR.'s post on his explanation)

   What do you mean by "synthesised harmonics"?

   Also, We can always measure the Fundimental  and related harmonics , but, we cannot measure "perceived harmonics", but, they can be modeled.

   Hammer
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luis Markson

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Re: Harmonics and fundamentals
« Reply #12 on: April 30, 2011, 08:44:54 am »

I was under the impression that "subharmonic" meant a perceived pitch below a series of synthesised harmonics.


  Hello Luis,

   In regards to one of your previous posts .... A perceived pitch and a fundimental can be be the same, or,   
   two separate things. (reread JR.'s post on his explanation)

Yep, I should have just said fundamental

   What do you mean by "synthesised harmonics"?

The process that plugins like Waves MAXbass use?

   Hammer


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.
JR
....

When you say " two closely spaced resonant notes" does this mean two separate sets of harmonics or two separate frequencies?


In the tympani example I offered the partials are actually 1.5x, 1.99x, and 2.44, with a common term of .5x that also is a valid fundamental pitch for those specific partials. For a little more background on this, 1.5x is the most prevalent pitch perceived when that drum is played, but .5x can be heard if the drum is struck a certain way, so the relative strength and duration of these partials also influences the perception of phantom fundamental. 


So in this example "1" is the fundamental? I am assuming 1.5x means one point five times...

So...

1 = fundamental
1.5x= perceived pitch
.5x = alternative perceived pitch (from performance style)

So here we have an example of a perceived pitch higher than the fundamental and at times lower. Or is there a fundamental at all?
« Last Edit: April 30, 2011, 08:47:18 am by luis Markson »
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John Roberts {JR}

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Re: Harmonics and fundamentals
« Reply #13 on: April 30, 2011, 10:06:39 am »




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.
JR
....

When you say " two closely spaced resonant notes" does this mean two separate sets of harmonics or two separate frequencies?
Two separate single notes with individual pitches. Drums do not make "sets of harmonics" like typical musical instruments because of their physical shape. Because the resonance waveform travels several different paths around and across the round membrane, there are pi terms in the ratios, and other obscure stuff. It gets even more complex with two headed drums, since the two heads couple together loosely and differently for different resonant series. Drums don't make overtones on integer harmonics but on non-musical ratios.   
Quote

In the tympani example I offered the partials are actually 1.5x, 1.99x, and 2.44, with a common term of .5x that also is a valid fundamental pitch for those specific partials. For a little more background on this, 1.5x is the most prevalent pitch perceived when that drum is played, but .5x can be heard if the drum is struck a certain way, so the relative strength and duration of these partials also influences the perception of phantom fundamental. 


So in this example "1" is the fundamental? I am assuming 1.5x means one point five times...

So...

1 = fundamental
1.5x= perceived pitch
.5x = alternative perceived pitch (from performance style)

So here we have an example of a perceived pitch higher than the fundamental and at times lower. Or is there a fundamental at all?


There is no, or only a very weak 1x fundamental. In a tympani the closed back severely damps the fundamental note, which would be the whole drumhead moving like a piston up and down as one. Since this fundamental would compress and rarify the air inside the drum. Overtones are moving up and down at different parts of the drumhead, so not damped by air pressure in back chamber. 

One minor terminology point,,, the physics guys call these phantom notes "virtual" notes, since they aren't really there, just like in some loudspeakers with severely attenuated fundamental, that fundamental note is virtual, not really present, while our mind fills in the missing information.

JR
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Re: Harmonics and fundamentals
« Reply #13 on: April 30, 2011, 10:06:39 am »


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