Which way is up? (Which way does a loudspeaker driver move?)

[René - Acculution.com]

I’m not interested in his explanation. He is a charlatan as far as I’m concerned. Your explanation is correct (as expected from you). My question was a technical question: Does overall polarity from microphone to speaker matter?

Absolute polarity? For test signals I can hear it and for music some people can. I cannot. The studies at present point to something similar.

 

[sarumbear]

Absolute polarity? For test signals I can hear it and for music some people can. I cannot. The studies at present point to something similar.

Do you happen to know of any research papers on absolute polarity?

 

[René - Acculution.com]

Absolute polarity? For test signals I can hear it and for music some people can. I cannot. The studies at present point to something similar.

I seem to remember a Danish one that came out recently but cannot quite remember.

 

[NTK]

I seem to remember a Danish one that came out recently but cannot quite remember.

Here is one.

AES E-Library » Observations on the Audibility of Acoustic Polarity

A number of experiments are described which show that absolute acoustic polarity is clearly audible in certain select cases of reproduced sound from acoustical instruments. The nature of the audible differences and the characteristics of the temporal signals which lend themselves to audibility...

www.aes.org

 

[kemmler3D]

Thanks for the post, I think I have seen this somewhere but totally forgot about it. It is definitely not intuitive until you understand that pressure comes from the velocity/acceleration and not displacement.

 

[René - Acculution.com]

Thanks for the post, I think I have seen this somewhere but totally forgot about it. It is definitely not intuitive until you understand that pressure comes from the velocity/acceleration and not displacement.

Thanks a lot. I try to fight the audiofoolery in the business, so this site is a nice venue for that. @amirm has done good.

 

[René - Acculution.com]

And in the infinite room, free-field, resistive external air-load only?

For an infinite tube the load is resitive so the piston will create pressure that correlates with its velocity. For free field we need to consider the fairly complex radiation impedance which can be highly resistive, but the Rayleigh integral still holds, so it now becomes important whether the phase is of the near field pressure or the far field ditto. But for the elevator picth "how does a loudspeaker generate sound" it is "inwards displacement creates positive sound pressure".

 

[-Matt-]

I think it would be closer to the physics (and more intuitive) to say that an outward accelerating surface creates positive pressure.

Remember that pressure is force per unit area and that force (on the air) is mass x acceleration.

Maximum positive acceleration ocurrs when the driver is a its most negative displacement (inside the cabinet).

At least for me saying...

"how does a loudspeaker generate sound" it is "inwards displacement creates positive sound pressure".

...is misleading (just like the video that is the topic of this thread). This is because the mind immediately thinks, ok so if I increase the displacement in the inward direction (which gives me negative velocity and maybe negative acceleration too) you are saying I will get positive pressure. This isn't correct. For the first half of the movement, from maximum extension to mid-point the inward motion of the driver will be rerefying the air immediately in front of it (reducing the pressure).

Edit: I'm referring to the free space case in the op here.

 

[René - Acculution.com]

I think it would be closer to the physics (and more intuitive) to say that an outward accelerating surface creates positive pressure.

Remember that pressure is force per unit area and that force (on the air) is mass x acceleration.

Maximum positive acceleration ocurrs when the driver is a its most negative displacement (inside the cabinet).

At least for me saying that "inward displacement creates positive sound pressure" is misleading. This is because the mind immediately thinks, ok so if I increase the displacement in the inward direction (which gives me negative velocity and maybe negative acceleration too) you are saying I will get positive pressure. This isn't correct. For the first half of the movement, from maximum extension to mid-point the inward motion of the driver will be rerefying the air immediately in front of it.

Edit: I'm refering to the free space case in the op here.

I am using Paul's language to get the point across. The animation shows the point. I would rather just go full blown math, but then I lose people. You are saying outward acceleration, so you have the same semantics issue. Positive acceleration means negative displacement for steady-state, and we are talking now about phasors. For those confused, just look at the movement in animation.

 

[-Matt-]

Or maybe you have a semantics issue - inwards displacement can't CAUSE this. It happens to occur at the same time as the peak acceleration. The acceleration is the CAUSE of the pressure increase.

If the driver remaind at a fixed large negative displacement - no pressure would be CAUSED.

 

[René - Acculution.com]

Or maybe you have a semantics issue - inwards displacement can't CAUSE this. It happens to occur at the same time as the peak acceleration. The acceleration is the CAUSE of the pressure increase.

If the driver remaind at a fixed large negative displacement - no pressure would be CAUSED.

It the driver is a fixed, there is also no acceleration. Please stop contaminating the thread.

 

[-Matt-]

It the driver is a fixed, there is also no acceleration. Please stop contaminating the thread.

Precisely - and so you acknowledge that it is the acceleration that causes the pressure. By relating the pressure to the displacement you make something that should be conceptually simple counter-intuitive. Congratulations - I leave the thread.

 

[René - Acculution.com]

Precisely - and so you acknowledge that it is the acceleration that causes the pressure. By relating the pressure to the displacement you make something that should be conceptually simple counter-intuitive. Congratulations - I leave the thread.

Well, to be fair, it is Paul who links displacement to pressure ;-) I say that, if anything, it is negative displacement and positive pressure that go together, which correlates with positive acceleration as I have stated here, and in several videos. But if there is no displacement there is no acceleration, and vice versa, as we are talking steady-state oscillatory motion.

 

[René - Acculution.com]

For comments in general, ask yourselves in your tone is conducive for other experts coming on here and giving material away for free. I know many peers who do not want to post anything on any forum due to the harsh comments and endless arguing that goes nowhere. I have fairly thick skin, but it would be great to get some more people on here to bust some myths and give insight in their respective fields.

 

[tmuikku]

Perhaps there is soon a AI plugin for the forum software which would warn about bad sentiment before publishing a post

 

[René - Acculution.com]

Perhaps ;.)

Perhaps there is soon a AI plugin for the forum software which would warn about bad sentiment before publishing a post ap

 

[sarumbear]

Here is one.

AES E-Library » Observations on the Audibility of Acoustic Polarity

A number of experiments are described which show that absolute acoustic polarity is clearly audible in certain select cases of reproduced sound from acoustical instruments. The nature of the audible differences and the characteristics of the temporal signals which lend themselves to audibility...

www.aes.org

I know of that one, read it a while ago. It was a topic of scientific research back in the 70s and 80s. It somehow concluded with the paper you referred to in in 1993. However, their conclusion was showing the effect of absolute polarity to be negligent at best.

While polarity inversion is not easily heard with normal complex musical program material, as our large-scale listening tests showed, it is audible in many select and simplified musical settings. Thus it would seem sensible to keep track of polarity and to play the signal back with the correct polarity to ensure the most accurate reproduction of the original acoustic waveform.

Possibly that is why no further research was done on the subject for the following 30 years. Recently a medical study concluded that absolute polarity does not effect the brain's recognition of sounds.

 

[René - Acculution.com]

I know of that one, read it a while ago. It was a topic of scientific research back in the 70s and 80s. It somehow concluded with the paper you referred to in in 1993. However, their conclusion was showing the effect of absolute polarity to be negligent at best.



Possibly that is why no further research was done on the subject for the following 30 years. Recently a medical study concluded that absolute polarity does not effect the brain's recognition of sounds.

Probably a very difficult topic to research. There might some training that can add to your ability to hear. And people are very different. Non-linearities in the ear are individual. For this particular topic, I would just trust my own ears.

 

[René - Acculution.com]

I know of that one, read it a while ago. It was a topic of scientific research back in the 70s and 80s. It somehow concluded with the paper you referred to in in 1993. However, their conclusion was showing the effect of absolute polarity to be negligent at best.



Possibly that is why no further research was done on the subject for the following 30 years. Recently a medical study concluded that absolute polarity does not effect the brain's recognition of sounds.

"On the audibility of all-pass phase in electroacoustical transfer functions" was the one I remembered now about phase in general.

 

[sarumbear]

"On the audibility of all-pass phase in electroacoustical transfer functions" was the one I remembered now about phase in general.

Thank you. It confirmed what I expected and you confirmed. Using test signals auditioned separately (like via headphones) you may hear absolute phase change but not when using music or speech source and using speakers.