The absolute pressure of an explosion is positive.
Since Earth has some air pressure then a vacuum is negative absolute pressure.

 

Hey Russ, If a church organist was playing the church organ yesterday and the Leslie speakers stopped at 60 degrees rotated (measuring clockwise from the top) from facing forward, then he went home and came back today with you, then started playing the church organ, what phase shift could you name from hearing the speakers that stopped yesterday?

Anwer: none. "Human hearing is generally considered to be insensitive to phase".

The sound is certainly phase shifted from what it would be if the speakers were facing forward. We know that because we can hear the phase shifting that happens when the speakers are spinning. (Otherwise, the Leslie Speaker Corporation would never have existed.) So, we humans can hear changes in phase, that is, relative to the sound just previous, but we can't get any phase information from a phase shifter that is not moving. Using the idea of relative phase, I came up with "absolute phase". If that is a worthless phrase, what do you call the thing that we can not perceive because the phase is not changing?

"Humans can not perceive_______________."

 

The absolute pressure of an explosion is positive.
Since Earth has some air pressure then a vacuum is negative absolute pressure.

I'm not sure why you mentioned this, but absolute pressure is zero-referenced against a perfect vacuum. Negative pressure can only exist in gauge pressure measurement, which is referenced against ambient air pressure.

 

Hey Russ, If a church organist was playing the church organ yesterday and the Leslie speakers stopped at 60 degrees rotated (measuring clockwise from the top) from facing forward, then he went home and came back today with you, then started playing the church organ, what phase shift could you name from hearing the speakers that stopped yesterday?

Anwer: none. "Human hearing is generally considered to be insensitive to phase".

The sound is certainly phase shifted from what it would be if the speakers were facing forward. We know that because we can hear the phase shifting that happens when the speakers are spinning. (Otherwise, the Leslie Speaker Corporation would never have existed.) So, we humans can hear changes in phase, that is, relative to the sound just previous, but we can't get any phase information from a phase shifter that is not moving. Using the idea of relative phase, I came up with "absolute phase". If that is a worthless phrase, what do you call the thing that we can not perceive because the phase is not changing?

"Humans can not perceive_______________."

I'm not intending to argue here - just to add something to the discussion.
When the speakers are spinning, the Doppler effect creates vibrato, or periodic change in pitch (tremolo, or change in volume, may also be created). This is easily detected by the ear. Since frequency (pitch) is the derivative of phase, I guess you could say you are detecting change in phase - but relative to what? Vibrato can be detected on a single tone (pure sine wave). The only chase change is relative to the average, because there are no harmonics or subharmonics to refer it to.

 

Ron, I would tend to buy into the idea that humans are hearing the cancellations and vibrato of a Leslie speaker system, and mistaking them for phase shift, except for studies on how human throats create the vowel sounds. The results of those experiments were described as phase changes. This information also led me to the idea that humans can judge relative phase changes (relative to the sound just previous).

What I seem to be missing is a vocabulary problem. Might it me, "static phase"? Humans can not perceive the static phase of a musical note? Like, humans can not tell which way the trumpet player is facing if they can't see him and he only blows one note.

 

Ron, I would tend to buy into the idea that humans are hearing the cancellations and vibrato of a Leslie speaker system, and mistaking them for phase shift, except for studies on how human throats create the vowel sounds. The results of those experiments were described as phase changes. This information also led me to the idea that humans can judge relative phase changes (relative to the sound just previous).

Are you talking about phase changes of the harmonics of a complex sound, relative to the fundamental, or phase changes in a single tone, or both? Or something else?

 

At the moment, I believe I'm talking about phase changes in a single tone. However, I have no problem visualizing that the phase changes of the harmonics carry information about direction, interfering surfaces, and distance. This leads to the idea of firing 3 shots when you are lost in the woods. It's hard to determine distance and direction of a single noise but giving 3 noises gives the listener time to move his ears and interpret the direction.

(While you were typing, I added the trumpet player example of a single note.)

 

Are you talking about phase changes of the harmonics of a complex sound, relative to the fundamental, or phase changes in a single tone, or both? Or something else?

If he's referring to a single tone, he'd be correct. If he means to phase-shift the entire composite waveform without independently shifting each frequency, then he'd also be correct. HOWEVER, if he means that each separate frequency that makes up a waveform, when phase shifted, still isn't detectible, then he'd be incorrect.

In the end, however, I'm thinking he's referring to one of the first two, and that he's correct, because he's being careful to use the word RELATIVE.

 

True, and the major point of this conversation. I contend that humans can not discriminate the phase of a single tone, no matter the harmonics that it has, but humans can detect phase changes in a stream of sounds and derive information from them. I just don't know what word is used besides "absolute phase" to describe the condition of the single tone from which we can not gather phase information.

 

Changes in phase of a single tone result in changes in frequency of that tone (f=dΦ/dt). Does the ear detect changes in phase, or in frequency, or both? Perhaps it doesn't matter what the mechanism is.

 

I'm not talking about a phase shift of 360 degrees per less than a second, multiple times in a row,which would change the frequency. I'm saying that everybody that can hear normally, can understand human speech, even if it is coming from Stephen Hawking's talking machine (a monotone speech synthesizer). The vowel sounds are produced by phase shifting, therefore, humans can detect relative phase changes in a continuous stream of sound.

Now, when the pitch is not changing, and the phase is not changing, and the amplitude is not changing, what is that phase relationship called, that phase relationship that humans are "generally considered insensitive to"?
(Trying to keep the focus on the question, not the possibilities of misinterpreting other aspects of an audio wave.)

 

The vowel sounds are produced by phase shifting

Phase shifting of what, relative to what?

 

The sound of a human voice is produced by a human. Phase shifting of a human voice is phase shifting of a human voice relative to what it was a moment ago.

I'm getting tired of repeating myself. If you don't know the word I am looking for, just say so.

 

Changes in phase of a single tone result in changes in frequency of that tone (f=dΦ/dt). Does the ear detect changes in phase, or in frequency, or both? Perhaps it doesn't matter what the mechanism is.

The Doppler effect on frequency and phase is different.
When the airplane is coming towards me its engine pitch is increasing, When it goes past me its pitch is decreasing. The frequency changes but I don't know and I don't hear what the phase does.

Changing the phase of a tone does not change its frequency!

 

Stephen Hawking's talking machine sounds awful. Surely a western engineer can program it to sound "normal" and hopefully not sound British!
"Wotah" does not sound like water.

 

OK. That does it. The first person to coin a phrase owns it. I just invented, "absolute phase" and "static phase" as meaning that humanly undetectable condition where the phase of a sound is not changing.

All hail Framptons Vo-corder, the machine that uses the fixed pitch, amplitude, and tamber of a guitar note, then uses Peter Frampton's mouth to shape the phase relationships. When it is not plugged in, people can not understand the words it is not shaping. That's because the phase of the sounds is not changing. The phase shifting is then, "static". I said so. I own it. Think of me when you use it.

 

A Vo-corder is a buzzer producing many harmonics..
Your mouth and maybe your nose resonates and filters some harmonics. Maybe the phase is changed.

 

The Doppler effect on frequency and phase is different.
When the airplane is coming towards me its engine pitch is increasing, When it goes past me its pitch is decreasing. The frequency changes but I don't know and I don't hear what the phase does.

Changing the phase of a tone does not change its frequency!

If you could make an instantaneous phase change in the second of two cycles,( not making any more phase changes from then on),comparing the period of the first cycle to that of the second,the second cycle would appear to be one cycle of a different frequency,as its period would be different to the previous one.
All other cycles after that point would revert to the original period,& hence frequency.
If you continue to change the phase,at a fast rate,both phase & frequency will continue to vary.

Before PLLs the classic way of producing crystal locked FM was to phase modulate an amplifier stage following the oscillator.

Looking at Frequency Modulation-v-Phase Modulation,the frequency deviation of FM is dependent on the amplitude of the modulating signal,& that of PM is dependent on both the amplitude & frequency of the modulating signal.

PM was turned into FM by tailoring the frequency content of the modulating signal.
Both PM & FM are commonly referred to as "Angle Modulation".

The phase/frequency domain gets more than a bit messy!
Even AM can produce incidental PM,because individual cycles are changed in amplitude,hence their zero crossing points are changed.
This is only slight in narrowband systems,but is measurable,& subject to a TV Standards specification for analog TV.

 

Actually Stephen hawking likes having that voice, as he believes that that voice has become his own, just as you or I would be comfortable with our.

I also believe he is British, so why wouldnt he want a British accent? I think you are confusing it with cockney.

 

Darn I thought his electronic voice had an American accent! It's definitely not what I would describe as "British" sounding.

Just be real glad he doesn't have an electronic voice with a New Zealand accent!