Topic by Jake Johnson

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Topic: Does Sound speed = Stiffness of the strings?

And does that mean that if we increase this setting, the higher freqs are moving faster than the lower freqs (which also move faster than they would if this parameter is set lower of course), or is this parameter just what it says---that all of the freqs move at the same rate relative to one another, but equally faster than the default setting?

Or would an increase in the Sound speed and a decrease in the string length instead = string stiffness?

I'm curious partly because I'd like to better understand the relationship of the sound speed to the other parameters that affect higher frequencies and thus upper partials, such as the string length and the partial sliders.

Thanks for any insights.

Last edited by Jake Johnson (01-03-2009 02:31)

Reply by Glenn NK

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Re: Does Sound speed = Stiffness of the strings?

So would I, but since the equation for sound is:

Velocity = frequency x wavelength,

The various frequencies don't travel at different velocities.

When the frequency increases, the wavelength decreases and vice versa.

I'm puzzled about the inclusion of speed of sound in version 3.0, because the only things that I am aware of that affect sound velocity are density, humidity, and temperature of the air (and density is a function of temperature).

In any given room or auditorium these three variables will essentially be identical, so at any given time, the speed of sound throughout a room will be constant.

If you want to shift the times the sound arrives at microphones, then move the mic closer or farther from the source - this will have more effect than changing the speed of sound within its normal range.

I'm puzzled by the range we can use (200 m/2 to 500 m/s):

At zero Celcius (30F), the calculated speed = 331.3 m/s

At 100 Celcius (212F), the calculated speed = 387 m/s

These values are for dry air.

I don't know how one would achieve values of 200 or 500 m/s in air.

I suppose that using a very slow speed is easier than moving the mic a couple miles/km away from the piano.

Glenn

conversion:  1 metre = 3.28084 feet

Last edited by Glenn NK (01-03-2009 05:46)
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Reply by Jake Johnson

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Re: Does Sound speed = Stiffness of the strings?

I should have been more clear--my impression is that when the strings are stiffened, they have more resistance, so when the hammer strikes, metallic upper partials and transients are given off first, before the entire string is vibrated. In other words, the high freqs don't actually travel faster. They're instead produced very slightly earlier, so they reach a given point outside the piano earlier than the lower partials, and thus appear to travel faster.

But of course this may not be what the Sound speed is all about. It may just be what it says it is--the sound travels faster.

Reply by Glenn NK

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Re: Does Sound speed = Stiffness of the strings?

Jake Johnson wrote:

I should have been more clear--my impression is that when the strings are stiffened, they have more resistance, so when the hammer strikes, metallic upper partials and transients are given off first, before the entire string is vibrated. In other words, the high freqs don't actually travel faster. They're instead produced very slightly earlier, so they reach a given point outside the piano earlier than the lower partials, and thus appear to travel faster.

But of course this may not be what the Sound speed is all about. It may just be what it says it is--the sound travels faster.


Everything I've read and heard states that when the strings are stiffer, they produce more inharmonic partials (out of tune?).  This is why the bass strings are harder to model than the high treble strings - they are much stiffer and their upper partials are more complex (out latest version has likely re-written the algorithms for the bass as it is much more realistic - and not as "clean" as it was).

The piano's unique sound results from the stiff strings (violin strings are much less stiff).

As for your title question - I don't know the answer.

Glenn

Last edited by Glenn NK (01-03-2009 06:51)
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Reply by Philippe Guillaume

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Re: Does Sound speed = Stiffness of the strings?

Hi Glenn and Jake,
the sound speed parameter that is available in the interface is the speed of the sound waves in the air, not in the solid parts (strings, soundboard..) where the sound speed remains unchanged.

The sound speed can vary with the frequency, that depends on where it is travelling: for example,
- the sound speed in the air does not vary with the frequency, at least in the linear acoustic model, which is the common model used as long as there are no explosions,
- it varies very slightly in a given string, the slight variation of waves speed with the frequency of the harmonics (called partials in that case) being precisely the inharmonicity phenomena due to the stifness of the string,
- it varies a lot in the soundboard. In particular, for the low frequencies where the sound speed in the soundboard is less than the sound speed in the air, there is a very bad energy transmission from soundboard to air and these low frequencies are almost not transmitted.

It is absolutely true that the sound speed in the air does not vary as much in the real world than what is proposed in Pianoteq. In fact, as this parameter was present in many pages of the code, we just thought it would be funny to let the user change it! Of course you go then beyond the real world: you enter the virtual world

Philippe Guillaume's Website

Reply by hyper.real

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Re: Does Sound speed = Stiffness of the strings?

guillaume wrote:

It is absolutely true that the sound speed in the air does not vary as much in the real world than what is proposed in Pianoteq. In fact, as this parameter was present in many pages of the code, we just thought it would be funny to let the user change it!

So when my friends listen to the new PTQ v3, I can say "My piano sounds faster than yours". Excellent! Already it is doing 340 m/s by default, which is rather better than a real piano would in England right now. In a moment I will work out how hot the ambient environment needs to be for my friends' pianos to radiate at the max 500 m/s... at a guess, it will be hotter even than the Hot Club de France - and therefore quite impossible to achieve in practise. PTQ wins!

Reply by feline1

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Re: Does Sound speed = Stiffness of the strings?

Anyone who's ever been to an open-air rock gig (e.g. at a festival) will know that the air can behave in a quite non-linear way and do horrible things to music! lol

Reply by Beto-Music

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Re: Does Sound speed = Stiffness of the strings?

In next pianoteq version Moddart will include the crash boom of sound barrier been broken.

:-)

Last edited by Beto-Music (01-03-2009 18:19)

Reply by Glenn NK

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Re: Does Sound speed = Stiffness of the strings?

guillaume wrote:

Hi Glenn and Jake,
the sound speed parameter that is available in the interface is the speed of the sound waves in the air, not in the solid parts (strings, soundboard..) where the sound speed remains unchanged.

The sound speed can vary with the frequency, that depends on where it is travelling: for example,
- the sound speed in the air does not vary with the frequency, at least in the linear acoustic model, which is the common model used as long as there are no explosions,
- it varies very slightly in a given string, the slight variation of waves speed with the frequency of the harmonics (called partials in that case) being precisely the inharmonicity phenomena due to the stifness of the string,
- it varies a lot in the soundboard. In particular, for the low frequencies where the sound speed in the soundboard is less than the sound speed in the air, there is a very bad energy transmission from soundboard to air and these low frequencies are almost not transmitted.

It is absolutely true that the sound speed in the air does not vary as much in the real world than what is proposed in Pianoteq. In fact, as this parameter was present in many pages of the code, we just thought it would be funny to let the user change it! Of course you go then beyond the real world: you enter the virtual world

Very interesting explanation - thank you.

I didn't know that the speed of sound in parts of the soundboard could be less than the speed in air.  The speed of sound varies in the soundboard because the stiffness and mass properties vary - it's made of a variable material - wood.  I would guess that's the main reason that why otherwise identical pianos can sound so different.  Yamaha's factory is able to produce tremendously consistent pianos with great quality so that hammers and actions are literally identical, but when it comes to the spruce soundboards, they are still faced with the variations that occur in one piece of wood (let alone the variation from piece to piece).  I know that when music schools are choosing a concert grand, they send at least one person to the factory to choose a piano from a "stable" of pianos that sounds "best" to them (touring pianists do this too), because they can vary considerably in tone.

The fact that the speed of sound in air doesn't vary as much as it can in Pianoteq isn't an issue in my mind - but I think it's important that anyone making adjustments realizes this.

If we were never able to change anything, then we wouldn't have the strange and wonderful sounds that were developed by the Moog synthesizers.

Being able to virtually change parameters is what frees us from tradition and enables us to move forward with creativity.

Glenn

PS - what I like about Pianoteq is that explosions aren't likely to occur that upsets my sound velocity settings.

Oh yes, I almost forgot - it's nice to have a music forum where the moderators are knowledgeable - in this case the knowledge is very reassuring.

Last edited by Glenn NK (01-03-2009 18:40)
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Reply by hyper.real

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Re: Does Sound speed = Stiffness of the strings?

I have no idea to what level of detail the soundboard is modelled in PTQ - for example, whether it currently can handle different bracing arrangements - this is probably commercially sensitive information. I can envisage PTQ, in a special "lab" version, being made available to piano manufacturers for research (at a very hefty price tag naturally).

Perhaps, then, it would be rather easier to model different strings.... silver, gold, platinum... niobium with a bit of americium thrown in (exclusively for the trans-Atlantic market)... should be easy enough - density of material should do it...

On the other hand, despite alleged competition, perhaps this is best left alone. Guitarists obsess about strings. Steel, bronze, phosphor-bronze; round cores or hexagonal cores; plastic covered or not (and do you put the plastic on before you wrap the cores, or afterwards?)...  Yes, they are all different, and too often it sounds like I am playing a wire fence and not a quality musical instrument. (I prefer gold plated, but cannot believe that that alone is responsible for the audible difference). And they age... you have to watch them like a hawk to catch them at their optimum sound... you can never go to the pub in case you miss the moment...

Reply by Jake Johnson

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Re: Does Sound speed = Stiffness of the strings?

Well, one request I made to Philippe was that the user be able to age the strings, which seems to be largely a matter of reducing the amplitude of the upper partials. (But there may be more to it.) For now, I reduce the upper partials manually, though I worry about not being able to control anything above the 9th partial.

Yes, my first instrument was guitar...

Reply by Beto-Music

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Re: Does Sound speed = Stiffness of the strings?

Well, I know that maybe it's silly try to add something, like silver strings, just because V-Piano have it.

But for comercial reasons it's interesting, jus to clear point that Moddart can also do it as well.

Last edited by Beto-Music (03-03-2009 22:51)