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Why is waveform asymmetric -- with different look on top than bottom?

Explorer ,
Dec 11, 2019 Dec 11, 2019

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I'm making narration files. When I look at my waveforms they are asymmetric: the waves look different on the top than the bottom. But the display is set up to look like it should be mirroring. Of course I don't even know what waveforms really mean. I don't know what the upper and lower parts represent. I've already saved it as Mono. 

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correct answers 1 Correct answer

Community Expert , Dec 11, 2019 Dec 11, 2019

This is quite normal. Happens a lot, especially with anything involving breath - like brass instruments and especially the human voice...

 

Basic explanation: What the waveform represents is the instantaneous vibrations of the air, as picked up by the microphone. By convention, positive pressure waves displace the diaphragm forwards, and this is represented by the waveform line moving upwwards. Because air is elastic, the pressure won't stay positive, and the waveform will revert back to the cen

...

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Community Expert ,
Dec 11, 2019 Dec 11, 2019

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This is quite normal. Happens a lot, especially with anything involving breath - like brass instruments and especially the human voice...

 

Basic explanation: What the waveform represents is the instantaneous vibrations of the air, as picked up by the microphone. By convention, positive pressure waves displace the diaphragm forwards, and this is represented by the waveform line moving upwwards. Because air is elastic, the pressure won't stay positive, and the waveform will revert back to the centre line. But because your voice is essentially a vibration of your vocal cords and they are elastic too, the forward movement of them will immediately be followed by a rearward movement which is a negative pressure change, with the waveform line moving downwards, and then back to the centre. If you ping a ruler over the edge of a table, you'll see the effect.

 

But, you will be asking, why the asymmetry then? This happens because when you speak or sing, you are breathing out. Rather than this being a vibration, the breath is only going in one direction - forwards. And that's going to displace the microphone diaphragm in a positive direction - so the waveform goes slightly higher up on the screen. It shows because the amount of air you breath out is a lot greater than the vibration displacement caused by your breath, and the diaphragm displaces a lot further. This is why we need, and should use, windshields with mics - they are primarily intended to diffuse the air blasts, and can often reduce the amount of asymmetry in the process.

 

If you see larger peaks going downwards, your mic is simply wired with a polarity inversion (often incorrectly described as 'out of phase'), and this doesn't matter - you can invert it again in Audition.

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Explorer ,
Dec 11, 2019 Dec 11, 2019

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Very cool! Thanks!

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Explorer ,
Dec 11, 2019 Dec 11, 2019

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PS: When I apply effects to a waveform why are the effects applied asymmetrically? I can see how voices and mics work that way but I'd think I'd want their modification to proceed proportionately ... but I notice the upper portion being transformed differently from the lower portion. ?

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New Here ,
Dec 13, 2023 Dec 13, 2023

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Such a useful question and brilliant answer.  I'm working with a chap who is new to radio, and he has a much deeper profile below the line.

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