The sound of a perfect square wave

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Discussion Overview

The discussion revolves around the theoretical sound of a perfect square wave, its harmonic content, and the implications of human hearing limitations. Participants explore the characteristics of square waves, their practical generation, and the auditory experience associated with them.

Discussion Character

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

Main Points Raised

  • Some participants note that a perfect square wave theoretically contains infinite odd harmonics, making it impossible to produce perfectly.
  • One participant suggests that if a perfect square wave could be produced, it might sound similar to a clarinet rather than being harsh and buzzy.
  • Another participant points out that human ears cannot hear frequencies above approximately 20 kHz, which could affect the perception of a perfect square wave compared to one with higher harmonics removed.
  • There is a mention of air potentially limiting the ramp rates of a generated square wave, which could affect its sound.
  • One participant proposes using Mathematica to explore the Fourier series of a square wave and to experience the sound by adding successive harmonics.
  • A later reply raises the idea that ultrasound might be perceived differently if transmitted directly to the skull, suggesting it does not resemble typical musical notes and has a unique sound.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the sound characteristics of a perfect square wave and the limitations of human hearing. There is no consensus on the exact nature of the sound or the implications of ultrasound perception.

Contextual Notes

Limitations include the assumptions about human hearing capabilities and the theoretical nature of a perfect square wave, which may not account for practical generation constraints.

Mohd Abdullah
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Hey guys,

It is stated that a 100% perfect square shaped wave have infinite odd harmonics and it is impossible to produced theoretically. But, assuming if a perfect square wave is produced, what would it sound like? I remember someone said it in Youtube it would actually sound like a clarinet instead sounding harsh and buzzy.
 
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It's a common alarm tone, and you can hear one yourself on the Wikipedia article on square waves.
 
Human ears can't hear anything above about 20 kHz*, so you couldn't hear the difference between a "perfect" square wave and one with harmonics above 20 kHz removed.

*That's for healthy young ears. The limit could be much lower for older ears.
 
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In addition to the limitation of human hearing, wouldn't the air also limit the ramp rates on something close to a generated square wave?
 
One fun thing you can try if you have access to Mathematica is to find the Fourier series for a square wave and then use the 'Play' function. You can add successive harmonics and try each one and then experience it for yourself.
 
DrGreg said:
Human ears can't hear anything above about 20 kHz*, so you couldn't hear the difference between a "perfect" square wave and one with harmonics above 20 kHz removed.

*That's for healthy young ears. The limit could be much lower for older ears.

Thanks for the response. But recently I hear people saying that ultrasound can be heard if it is fed directly to the skull, I think it doesn't sound like any of the musical notes for example, the highest note of the piano. I think it sounds weird and unique. Thoughts?
 

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