8 ms·

> If you hear a sound of frequency f and others of frequency 2f, 3f, etc then there's a good chance these sounds come from the same object, due to the physical

> If you hear a sound of frequency f and others of frequency 2f, 3f, etc then there's a good chance these sounds come from the same object, due to the physical principle of resonance. And so our perception of sound evolved to reflect this... Wow that's interesting enough to share as a standalone post, so I took the liberty! Thanks for the link!

enriquto 6y ago
The quoted sentence seems false to me. Most physical objects do not have naturally harmonic vibration spectra. The vibration modes are not integer multiples ofthe fundamental (except for a vibrating string). Only the finely tuned western instruments do. So this is a somewhat backwards argument.
- jacquesm 6y ago
  > Most physical objects do not have naturally harmonic vibration spectra. What is your basis for saying this? A large number of physical objects, solids as well as hollow can be approximated as systems of springs, surfaces and tensile elements, which all have some frequency response. It isn't rare at all for a physical system to have a very sharp resonant peak in its frequency response, to the point that you'll often find mechanisms to dampen that response so the structure will survive certain inputs.
  - enriquto 6y ago
    what you are describing is a graph. The laplacian spectrum of a graph is arbitrary.
    - PEJOE 6y ago
      Every rigid object has a fundamental frequency, regardless of whether you put it on a graph.
      - enriquto 6y ago
        Sure. But the other frequencies need not be integer multiples of the fundamental.
        jacquesm 6y ago
        They don't have to, but usually those integer multiples will be present as well. Whether they are dominant or not is another matter but it is quite hard to design something in such a way that if it has a natural resonance at a certain frequency that integer multiples will not be present in the response spectrum. A typical object will have multiple modes of resonance as well.
        enriquto 6y ago
        > usually those integer multiples will be present as well "usually", under what probability model? A random 3d or 2d shape will have zero harmonic partials with probability 1. What is hard to achieve is having even a few harmonic partials. A rectangular wooden piece is painstakingly carved to have a couple of harmonic partials, in order to become a xylophone or marimba bar.
        jacquesm 6y ago
        Yes, but shapes are not usually random. Bars, cylinders, cubes, rectangles, squares and circles are everywhere. That does not mean that they will have a string like attenuation curve for those higher harmonics, but they'll be there.
        fuckf4ce 6y ago
        > Yes, but shapes are not usually random. Bars, cylinders, cubes, rectangles, squares and circles are everywhere. While there are some exceptions, this is skewed in the modern industrial world. If we're making evolutionary scale arguments about sound perception it's a much tougher sell.
  - HelloNurse 6y ago
    Many objects don't have audible vibration modes (infrasonic, ultrasonic, so damped that sounds are too brief and too quiet) but it doesn't mean that they don't vibrate.
- kortex 6y ago
  You have the causality backwards though. It isn't saying most objects emit quantized overtones. But if you hear quantized overtones, there's a very good chance they are from the same source. It's not just strings, either. Drum heads have varying degrees of quantized modes.
- OscarCunningham 6y ago
  The code itself also contradicts that sentence. Notice that the first roughness graph doesn't have any local minima at rational numbers. It's only when the overtones are added to the notes (at integer multiples of the fundamental frequency) that the minima appear. So the code thinks that human ears don't detect integer multiples specifically, they just detect sounds whose overtones line up with each other.
  - sideshowb 6y ago
    Good point, but our ears definitely do perceive the 2 to 1 ratio. Maybe that particular phenomenon is better analysed through the usual pschoacoustic approach of "at what point do we stop perceiving one sound and start perceiving two "?
- IggleSniggle 6y ago
  I don't think so. If a sound persists long enough to hear its continuation, then its partials are generally going to be harmonic. Non-resonant frequencies will have a tendency to dissipate very quickly, unless they are explicitly designed to warble between resonances (like a gong or similar).
sideshowb 6y ago
@harperlee no worries about the share, it's great to see the variety of responses on the other thread

enriquto 6y ago

The quoted sentence seems false to me. Most physical objects do not have naturally harmonic vibration spectra. The vibration modes are not integer multiples ofthe fundamental (except for a vibrating string). Only the finely tuned western instruments do. So this is a somewhat backwards argument.

jacquesm 6y ago
> Most physical objects do not have naturally harmonic vibration spectra. What is your basis for saying this? A large number of physical objects, solids as well as hollow can be approximated as systems of springs, surfaces and tensile elements, which all have some frequency response. It isn't rare at all for a physical system to have a very sharp resonant peak in its frequency response, to the point that you'll often find mechanisms to dampen that response so the structure will survive certain inputs.
- enriquto 6y ago
  what you are describing is a graph. The laplacian spectrum of a graph is arbitrary.
  - PEJOE 6y ago
    Every rigid object has a fundamental frequency, regardless of whether you put it on a graph.
    - enriquto 6y ago
      Sure. But the other frequencies need not be integer multiples of the fundamental.
      - jacquesm 6y ago
        They don't have to, but usually those integer multiples will be present as well. Whether they are dominant or not is another matter but it is quite hard to design something in such a way that if it has a natural resonance at a certain frequency that integer multiples will not be present in the response spectrum. A typical object will have multiple modes of resonance as well.
        enriquto 6y ago
        > usually those integer multiples will be present as well "usually", under what probability model? A random 3d or 2d shape will have zero harmonic partials with probability 1. What is hard to achieve is having even a few harmonic partials. A rectangular wooden piece is painstakingly carved to have a couple of harmonic partials, in order to become a xylophone or marimba bar.
        jacquesm 6y ago
        Yes, but shapes are not usually random. Bars, cylinders, cubes, rectangles, squares and circles are everywhere. That does not mean that they will have a string like attenuation curve for those higher harmonics, but they'll be there.
        fuckf4ce 6y ago
        > Yes, but shapes are not usually random. Bars, cylinders, cubes, rectangles, squares and circles are everywhere. While there are some exceptions, this is skewed in the modern industrial world. If we're making evolutionary scale arguments about sound perception it's a much tougher sell.
- HelloNurse 6y ago
  Many objects don't have audible vibration modes (infrasonic, ultrasonic, so damped that sounds are too brief and too quiet) but it doesn't mean that they don't vibrate.
kortex 6y ago
You have the causality backwards though. It isn't saying most objects emit quantized overtones. But if you hear quantized overtones, there's a very good chance they are from the same source. It's not just strings, either. Drum heads have varying degrees of quantized modes.
OscarCunningham 6y ago
The code itself also contradicts that sentence. Notice that the first roughness graph doesn't have any local minima at rational numbers. It's only when the overtones are added to the notes (at integer multiples of the fundamental frequency) that the minima appear. So the code thinks that human ears don't detect integer multiples specifically, they just detect sounds whose overtones line up with each other.
- sideshowb 6y ago
  Good point, but our ears definitely do perceive the 2 to 1 ratio. Maybe that particular phenomenon is better analysed through the usual pschoacoustic approach of "at what point do we stop perceiving one sound and start perceiving two "?
IggleSniggle 6y ago
I don't think so. If a sound persists long enough to hear its continuation, then its partials are generally going to be harmonic. Non-resonant frequencies will have a tendency to dissipate very quickly, unless they are explicitly designed to warble between resonances (like a gong or similar).

sideshowb 6y ago

@harperlee no worries about the share, it's great to see the variety of responses on the other thread