Low Frequency Wave Transmission Through Barriers

  • Context: Undergrad 
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Discussion Overview

The discussion revolves around the transmission of low-frequency waves through barriers, exploring both qualitative explanations and mechanical analogies without relying on mathematical derivations. Participants consider various types of barriers and the nature of the waves involved, including sound waves and electrical signals.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that barriers generally transmit more low frequencies than high frequencies, suggesting a qualitative explanation is sought.
  • Others argue that low pass filters can illustrate mechanical damping systems that reduce high frequencies, indicating that the relationship may not be straightforward.
  • A participant questions the specific type of barrier and wave being discussed, noting that some barriers may resonate at certain frequencies, affecting transmission.
  • Another participant clarifies that they are referring to barriers like capacitors in RC high pass filters and ordinary building walls, emphasizing the frequency-dependent reflection and transmission of waves.
  • One participant provides an intuitive explanation regarding the resonance of walls, describing how the physical movement of the wall at certain frequencies allows for energy transmission, suggesting this aligns with the qualitative inquiry posed.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between frequency and transmission through barriers, with no consensus reached on the qualitative explanations or the specific mechanisms involved.

Contextual Notes

Participants reference various types of barriers and waves, indicating that the discussion may depend on specific definitions and contexts, which remain unresolved.

Who May Find This Useful

Individuals interested in wave mechanics, acoustics, electrical engineering, and those exploring qualitative explanations in physics may find this discussion relevant.

neworder1
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Any barrier passes more low frequencies than high (i.e. the amplitude of transmitted wave is higher when the frequency is lower). This can be derived form wave equations, but I wonder whether there is any qualitative explanation for this, not resorting to mathematics?
 
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Any barrier passes more low frequencies than high
Not necessarily, low pass filters are probably easier to think about mechanically where a damping system will reduce high frequencies.
In electroncis it's often more common to filter out lower frequency eg 60Hz interference while transmitting a high frequency signal.
 
neworder1 said:
Any barrier passes more low frequencies than high (i.e. the amplitude of transmitted wave is higher when the frequency is lower). This can be derived form wave equations, but I wonder whether there is any qualitative explanation for this, not resorting to mathematics?

What barrier and what kind of waves are you asking about? Some barriers will resonate at particular frequencies, and hence pass a band of frequencies and reflect the others.
 
I mean barriers like a capacitator in RC high pass filter (change of voltage) or an ordinary building wall (sound wave). When a wave passes from one medium to another some frequencies are reflected more than the others - I wonder whether in the example above it can be shown "qualitatively", without wave equations.
 
You don't use the wave equation to solve for the frequency response of an RC filter.

On the wall example, you can intuitively see how at the fundamental resonance frequency, the middle of the wall will alternately bulge a bit out and back in, at the sound frequency that matches that wall resonance (which is determined by the rigidity and size of the wall). Since the wall is physically moving back and forth, it transmits some of the longitudinal sound wave's energy through to the other side. Is that the kind of non-equation intuitive explanation that you are looking for?
 

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