space is not a dimension ?

Quote from: silverprout on 2018-07-18 22:28:51

space is not a dimension ?

A location in space can be described with three dimensions, and space/time (in certain circumstances) 4 dimensions.  However, the number of dimensions for a sound pressure measurement is scalar pressure + time.  One can mix multiple pressure measurements (along with other intelligence in the data -- incl spatial location of the measurements), then allow the sound to help describe the environment (including the source locations.)  This description of the environment is what sonar does (and how the brain calculates the spatial relationships.)

John

Quote from: jsdyson on 2018-07-19 01:55:41

Quote from: silverprout on 2018-07-18 22:28:51

space is not a dimension ?

A location in space can be described with three dimensions, and space/time (in certain circumstances) 4 dimensions.  However, the number of dimensions for a sound pressure measurement is scalar pressure + time.  One can mix multiple pressure measurements (along with other intelligence in the data -- incl spatial location of the measurements), then allow the sound to help describe the environment (including the source locations.)  This description of the environment is what sonar does (and how the brain calculates the spatial relationships.)

John

Are you a vacuum cleaner designer ?
(The smallish high RPM motors embedded in the dyson appliances are horribly noisy and is a real pain to endure)

A mathematician should think about the Inverse-square law, no ?

environment given multiple scalar sound measurements vs. time.
John

Quote from: jsdyson on 2018-07-19 19:06:23

environment given multiple scalar sound measurements vs. time.
John

I don't understand "scalar" part of the sentence, you mean that we can vectorize the sound propagation with a microphone array... how ?
It can only be performed in the far field IMO (if it is possible)

IMHO the 1D point of view don't conceptualize the reality because all audio measurements are performed by people who have the sound field in mind.

If a person has a picture of what they expect the sound field to be -- and then uses a singular real data point, aren't they really sustituting 'fake' (not necessarily invalid) effective data points for real ones? 

Quote from: jsdyson on 2018-07-19 22:40:46

If a person has a picture of what they expect the sound field to be -- and then uses a singular real data point, aren't they really sustituting 'fake' (not necessarily invalid) effective data points for real ones? 

The more data points the better which, as I recall, is kind of why we moved from mono to stereo back in the 1950's. 

But please note that your ears have only two data points, yet you are able to hear a three dimensional sound field.  If two ears can do it, why can't two microphones?

However, to be intellectually honest -- that information that the human brain can synthesize, the ability to use the shape/structure of the ears' environment and the hard-core physics of the environment -- that is GREATER than just the two sensors.  That is why more information can be gleaned.

Quote from: jsdyson on 2018-07-20 03:59:50

However, to be intellectually honest -- that information that the human brain can synthesize, the ability to use the shape/structure of the ears' environment and the hard-core physics of the environment -- that is GREATER than just the two sensors.  That is why more information can be gleaned.

Right. You could put it this way: There are a lot of assumptions built into human hearing. Some of them are learned, others are "wired in". This is a reason why hearing can be fooled and occasionally produces wrong impressions.

Stereo only works because of this. A phantom source isn't anything physical. There is no phantom source in the sound field. It is the post-processing of the signal from our two sensors (ears), which creates (the impression of) the phantom source.

You could say that with stereo, human hearing gets it consistently wrong. Stereo is a way of using a specific deficiency of human hearing to fool it into hearing a 3D sound field that isn't there. We all know that this illusion breaks down easily (sweet spot etc.).

If we don't distinguish between the two, audiophile-land can be very confusing, and is probably a major reason for all of the 'audio-religion', and wine-tasting-esque descriptions of audio out there.  There are real technical descriptions available, but until the idea of SOUND and HEARING are seperated, then a lot of people are going to stay confused, but not know it.

Quote from: silverprout on 2018-07-19 22:23:23

IMHO the 1D point of view don't conceptualize the reality because all audio measurements are performed by people who have the sound field in mind.

If a person has a picture of what they expect the sound field to be -- and then uses a singular real data point, aren't they really sustituting 'fake' (not necessarily invalid) effective data points for real ones?  No matter what you are imagining, there has to be some kind of framework -- and in space, there are normally 3 dimensions.  One can abstractly create more dimensions for some kind of analysis purpose, but in reality there are three dimensions in space.   Adding more dimensions isn't just describing space, but rather some kind of hyperspace (no scifi here.)

John

Quote from: jsdyson on 2018-07-19 22:40:46

Quote from: silverprout on 2018-07-19 22:23:23

IMHO the 1D point of view don't conceptualize the reality because all audio measurements are performed by people who have the sound field in mind.

If a person has a picture of what they expect the sound field to be -- and then uses a singular real data point, aren't they really sustituting 'fake' (not necessarily invalid) effective data points for real ones?  No matter what you are imagining, there has to be some kind of framework -- and in space, there are normally 3 dimensions.  One can abstractly create more dimensions for some kind of analysis purpose, but in reality there are three dimensions in space.   Adding more dimensions isn't just describing space, but rather some kind of hyperspace (no scifi here.)

John

We have a tension, an intensity and time at the input of the loudspeaker coil, we can also try to link the voltage and the intensity through an imaginary thing called phase... also linked with the coil motion... and the air motion... abstraction is infinitely complex.
I only matter about what i'm imagining when i perform a measurement, the loudspeaker surface is radiating within two modes, a pistonic and radiative motion that generate a complex soundfield composed of a cloud of air of physical elementary particles moving relatively coherentely with the emissive surfaces when you are close to them and doing unpredictible things when you get farther (everyting is also highly impacted by the signals)
You should also add all the reflexions and the air volume when you are in a room, as you are probably awared of expertise is everthing and a clever measurement can validate a very complex theory.
If we don't matter about how many dimensions to use, could you say if there is a way to beat a human brain in this field of competence ?

... i'm not as intelligent as Garry Kasparov, but deeper blue is still biting the dust.

All of the physical stuff being described can be modeled by a competent mechanical/electrical engineering team.  Modeled so accurately that a 'virtual' copy of the speaker can likely predict the behavior incredibly accurately (including the enviornment.)  All of the things like 'standing waves' on a speaker diaphragm are 'old hat', and can be predicted fairly well.

Quote from: jsdyson on 2018-07-21 00:39:12

All of the physical stuff being described can be modeled by a competent mechanical/electrical engineering team.  Modeled so accurately that a 'virtual' copy of the speaker can likely predict the behavior incredibly accurately (including the enviornment.)  All of the things like 'standing waves' on a speaker diaphragm are 'old hat', and can be predicted fairly well.

It is perhaps time to add a new knowledge to your personal culture... it hadn't been done yet, i would be very pleased to see one of that kind of study before my death.
In an effort to stay in touch with the topic, i can say that the sound propagation in our environement (air, room and objects) is infinitely complex and unpredictible by nature, and the 1D point of view is a good explanation for the children but not for an adult.

The environment can also be included in models.  But, at a certain point, it is silly to go into more detail.  There are so many kinds of environments, that a generally applicable design will work well.

This is all about the nonsensical 'audiophile' reasoning (and pseudo-wine tasting language) vs. the real state of engineering and research.  There are still alot of snake oil salesemen selling inferior product with 'personality' vs. very accurate equipment.
I vote on the side of real, accurate engineering vs. the overly expensive snake oil.  Too many people without real engineering backgrounds get taken in by snake oil marketing.
In some cases, some of the snake oil marketing IS backed by sound engineering, but that is really kind of sad.  People are being dys-educated into being idiots in the guise of pseudo-tech.
Real world engineering thinking and work is where the real advances are made (or, in the case of a lot of legacy technologies -- e.g. most audio stuff), already have been made.  Please refer to the rather curious love of vacuum tubes (definitely legacy, but cute technology.)  It is damned hard to get really good distortion and bandwidth on tube gear, but they try (barely succeeding) -- and some make money at it, esp with the snake oil behind it.  (I started designing with 'tubes' years ago -- I know what I am talking about.)
My guess is that because audio (in almost all ways) has advanced almost as far as it can -- some of the marketeers who take advantage of the non-engineering-knowing people and instead look backwards.  Sure -- 'adequate' quality can be had with 'tubes', but why do it?   Markettering (coined word -- marketing based upon feeling instead of fact), knowing that selling goods based upon technical advantage is now nearly specious (given competent, up-to-date design.)
John

Quote from: jsdyson on 2018-07-21 00:39:12

The environment can also be included in models.  But, at a certain point, it is silly to go into more detail.  There are so many kinds of environments, that a generally applicable design will work well.

All good measuring softwares that i've tested are unable to corellate the measurements and the theory, the calculated room modes are always wrong.
The devil is in the details, and the lack of these details is killing the math models accuracy.

Quote from: jsdyson on 2018-07-21 00:39:12

This is all about the nonsensical 'audiophile' reasoning (and pseudo-wine tasting language) vs. the real state of engineering and research.  There are still alot of snake oil salesemen selling inferior product with 'personality' vs. very accurate equipment.
I vote on the side of real, accurate engineering vs. the overly expensive snake oil.  Too many people without real engineering backgrounds get taken in by snake oil marketing.
In some cases, some of the snake oil marketing IS backed by sound engineering, but that is really kind of sad.  People are being dys-educated into being idiots in the guise of pseudo-tech.
Real world engineering thinking and work is where the real advances are made (or, in the case of a lot of legacy technologies -- e.g. most audio stuff), already have been made.  Please refer to the rather curious love of vacuum tubes (definitely legacy, but cute technology.)  It is damned hard to get really good distortion and bandwidth on tube gear, but they try (barely succeeding) -- and some make money at it, esp with the snake oil behind it.  (I started designing with 'tubes' years ago -- I know what I am talking about.)
My guess is that because audio (in almost all ways) has advanced almost as far as it can -- some of the marketeers who take advantage of the non-engineering-knowing people and instead look backwards.  Sure -- 'adequate' quality can be had with 'tubes', but why do it?   Markettering (coined word -- marketing based upon feeling instead of fact), knowing that selling goods based upon technical advantage is now nearly specious (given competent, up-to-date design.)
John

The only way to go is to calculate and measure by yourself IMHO, the market is saturated of junk product and the good ones are also junk when used inappropriately.

Quote from: sizetwo on 2018-07-15 14:45:50

Thanks for not making me feel quite so silly. My friend is a maths professor, and I believe his assertion. I just don't understand how you can have that type of information in a single dimension (time).

Perhaps you can get him to clarify.

The function y=f(x) is one dimensional. A two dimensional function would have the form y=f(x1,x2).

Quote from: saratoga on 2018-07-15 18:47:21

The function y=f(x) is one dimensional. A two dimensional function would have the form y=f(x1,x2).

Why not y=f(x,t) ?

Related http://www.feynmanlectures.caltech.edu/I_47.html

I'd like to point out that I think much of the confusion here is regarding the usage of the word "dimension". The graph of a one-variable function y = f(x) is indeed two-dimensional (that is, you need two dimensions to draw the function) even if you only have one independent variable x.

To the OP; you say in your first message, "I would assume sound also has at least two axis, one representing time" -- that is absolutely correct, sound is a wave that propagates through space and time, so you need at least one spatial independent variable and the time independent variable; a third variable also exists here, the pressure, which is the dependent variable, which, when the wave equation is solved, gives the pressure as a function of time and space.

Then you say, "My friend makes the claim that there only is one". Could it be possible your friend is thinking of the typical expansion-compression cycle, like that of a Slinky, which goes back and forth in one spatial dimension but otherwise also advances in time?

As others here have pointed out, it'd be useful to see, verbatim, what your friend says, from which we can attempt to deduce what was meant, and if needed, correct what they said.