Classical uncertainty principle

  • #1

Main Question or Discussion Point

What assumptions underlie the classical uncertainty principle? The principle doesn't seem to apply when I want to know the precise pitch of a tone from a bowed violin string, since I can measure the duration (as precisely as I want) of the beats produced when I interfere it with a sine wave of known frequency. The violin string is fairly simple oscillator, not a completely unknown signal, and its frequency should be constant and stable. So, does the uncertainty principle apply only when you don't know the nature of the tone you're trying to determine the pitch of?
 

Answers and Replies

  • #2
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
15,921
5,633
What assumptions underlie the classical uncertainty principle? The principle doesn't seem to apply when I want to know the precise pitch of a tone from a bowed violin string, since I can measure the duration (as precisely as I want) of the beats produced when I interfere it with a sine wave of known frequency. The violin string is fairly simple oscillator, not a completely unknown signal, and its frequency should be constant and stable. So, does the uncertainty principle apply only when you don't know the nature of the tone you're trying to determine the pitch of?
The uncertainty principle has nothing to do with violin strings, as far as I know, partly because they are macro-sized objects and everything averages out. The HUP is about micro-level things (electrons, etc) taken individually.
 
  • #3
f95toli
Science Advisor
Gold Member
2,952
448
The uncertainty principle has nothing to do with violin strings, as far as I know, partly because they are macro-sized objects and everything averages out. The HUP is about micro-level things (electrons, etc) taken individually.
The OP is referring to the classical (AKA mathematical) UP which basically is a consequence of how the Fourier transform (and our definition of frequency) work.
In this context all it means is that if you want to measure the pitch of the string with a good accuracy you need to measure for a long time and vice versa.
 
  • #4
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
15,921
5,633
The OP is referring to the classical (AKA mathematical) UP which basically is a consequence of how the Fourier transform (and our definition of frequency) work.
Ah. Thanks for giving me that understanding.
 

Related Threads on Classical uncertainty principle

Replies
4
Views
1K
Replies
2
Views
3K
Replies
12
Views
4K
Replies
4
Views
961
  • Last Post
Replies
9
Views
1K
  • Last Post
3
Replies
53
Views
7K
  • Last Post
Replies
0
Views
1K
  • Last Post
Replies
3
Views
2K
Top