Re: [Sursound] Acoustic properties of round rooms ?

[David Pickett]

At 00:26 08-03-16, Sampo Syreeni wrote:

On 2016-03-07, David Pickett wrote:


Sorry, I should shave before writing.  I meant magnetron, not klystron...


Magnetrons are self-oscillating sources of microwave radiation. Of 
the fringed, multiplied, physical, secondary oscillator kind. 
Klystrons on the other hand are linear electron beam devices which 
are used as high gain, high power amplifiers.


I don't mean to be rude, but how on earth do you mix those tubes 
togerher? To me they seem totally different, both in construction, 
and in their actual use.


Simply because I havent used or seen one since 1966, when I was 
building solid state oscillators to replace them.


David

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Re: [Sursound] Acoustic properties of round rooms ?

[Sampo Syreeni]

On 2016-03-07, David Pickett wrote:

Sorry, I should shave before writing.  I meant magnetron, not 
klystron...


Magnetrons are self-oscillating sources of microwave radiation. Of the 
fringed, multiplied, physical, secondary oscillator kind. Klystrons on 
the other hand are linear electron beam devices which are used as 
high gain, high power amplifiers.


I don't mean to be rude, but how on earth do you mix those tubes 
togerher? To me they seem totally different, both in construction, and 
in their actual use.


I havent looked in detail, but they are, as I expected, high Q 
devices, which is a much better way of putting what I was trying to 
say earlier in a rather fumbly way.


The Magnetron is a very high Q device, by design. It's engineered to be 
a primary oscillator in the microwave range. At the same time, the 
Klystron cannot be analyzed via LTI-minded Q math. It does have its 
resonances, and its intrinsic bandwidth, but the reason it's used in 
e.g. radar systems is precisely it's capability of amplifying, via 
somewhat nonlinear processes within the electron beam, a broader 
frequency range than any tube thingy which came before it.

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] Acoustic properties of round rooms ?

[David Pickett]

Sorry, I should shave before writing.  I meant magnetron, not 
klystron...  There is a lot of stuff if you google circular microwave 
cavities.  I havent looked in detail, but they are, as I expected, 
high Q devices, which is a much better way of putting what I was 
trying to say earlier in a rather fumbly way.


David 


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Re: [Sursound] Acoustic properties of round rooms ?

[David Pickett]

I wrote:

>> I would look to see if any work has been done on the behaviour of
>> comparable frequency transveres radio waves in circular waveguide.

I mean comparable in terms of the ratios of the diameter of the 
waveguide and the wavelength of the signal.  However, since I cant 
see a use for such in a long guide, it may not have been 
done.  Cavities, on the other hand with a limited height...  (Klystrons?)


David

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Re: [Sursound] Acoustic properties of round rooms ?

[Augustine Leudar]

Willdo

On 6 March 2016 at 14:51, David Pickett  wrote:

>
> I visualize this by starting with the four walls or a square room.  There
> will be two similar horizontal sets of modes at the same frequencies.  Now
> make it octagonal and there are four sets of modes at the same
> frequencies.  Keep doing this and in the limit you arrive at a circular
> wall with an "infinite" number of modes...  Of course, there is some
> friction, but the effect would surely still be to have greater response at
> certain frequencies and not much in between them.
>
> I would look to see if any work has been done on the behaviour of
> comparable frequency transveres radio waves in circular waveguide.
>
> David
>
>
>
> At 12:48 06-03-16, Augustine Leudar wrote:
> >Im actually working on a sound installation which is involved with
> acoustic
> >archeology in which Im hoping to experiments with resonances , this kind
> of
> >thing :
> >
> >http://www.otsf.org/archaeoacoustics.html
> >
> >In this case a huge circular henge (3.5  m high banks)  180 m in diameter.
> >
> >https://en.wikipedia.org/wiki/Giant%27s_Ring
> >
> >Obviously with no roof resonance will not be as pronounced but there is
> >still likely to be some sort of modal behaviour, especially if there had
> >been many people singing/chanting etc . Apparently you cant work out modes
> >for circular structures in the normal way by halving wavelength in
> relation
> >to room dimensions etc  A family member of mine is a physicist and
> >suggested this might be useful to work out modes for an open circular
> >structure :
> >
> >https://en.wikipedia.org/wiki/Vibrations_of_a_circular_membrane#Animat
> >ions_of_several_vibration_modes
> >
> >
> >
> >Then the following equation :
> >
> >Lowest frequency will be from longest wavelength which is 2 X pi X r/2.404
> >(where r is radius of your circle) the next frequency has wavelength 2 pi
> >r/3.83 = 1.64  x radius. And then 2 pi r/5.135 etc etc
> >
> >However this gives very long wavelengths - the highest mode is 11.61
> there,
> >but for me to calculate audible modes I would need numbers in this series
> >above 150 or so (to get shorter audible wavelengths.
> >Could anyone give numbers in the same series of numbers but above 150 ?
> >
> >
> >
> >
> >
> >
> >
> >
> >On 5 March 2016 at 21:31, Martin Leese 
> >wrote:
> >
> >> Augustine Leudar wrote:
> >>
> >> > Ive had a search online but cant really find much literature about
> this.
> >> > Can anyone tell me anything about the acoustics of circular
> rooms/spaces
> >> ?
> >> > How to standing waves behave in circular spaces ?
> >>
> >> There was a discussion several years ago in
> >> one of the rec.audio.* newsgroups on standing
> >> waves in *spherical* rooms.  Unfortunately,
> >> Google Groups has deleted all the older posts,
> >> but this post might be it:
> >> https://groups.google.com/forum/#!search/"spherical$20room"$20audio/
> >> rec.audio.pro/hLCCrmlSFdw/Lq_80PhAZQ0J
> >>
> >> (In case the link does not work, I went to
> >> groups.google.com and searched for:
> >> "spherical room" audio
> >> with the double quotes.)
> >>
> >> Regards,
> >> Martin
> >> --
> >> Martin J Leese
> >> E-mail: martin.leese  stanfordalumni.org
> >> Web: http://members.tripod.com/martin_leese/
> >> ___
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> >> edit account or options, view archives and so on.
> >>
> >
> >
> >
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Re: [Sursound] Acoustic properties of round rooms ?

[Augustine Leudar]

Hi Martin,
I have been reading Salfords study. However the acoustics would be a bit
different in stonehenge to a solid raised bank henge (no stones, so gaps
between stones so no acoustic shadowing etc etc)

On 6 March 2016 at 22:00, Martin Leese 
wrote:

> Augustine Leudar wrote:
>
> > Im actually working on a sound installation which is involved with
> acoustic
> > archeology in which Im hoping to experiments with resonances , this kind
> of
> > thing :
> >
> > http://www.otsf.org/archaeoacoustics.html
> >
> > In this case a huge circular henge (3.5  m high banks)  180 m in
> diameter.
>
> The acoustics of stonehenge (both original
> and completed replicas) have been discussed
> on the list previously.  If you are interested,
> search the archives for:
> Subject: Stonehenge's eerie sounds revived
> Date: Fri, 27 Apr 2012
>
> Subject: Gran Sasso - first impressions
> Date: Mon, 18 Feb 2013
>
> Regards,
> Martin
> --
> Martin J Leese
> E-mail: martin.leese  stanfordalumni.org
> Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Acoustic properties of round rooms ?

[Martin Leese]

Augustine Leudar wrote:

> Im actually working on a sound installation which is involved with acoustic
> archeology in which Im hoping to experiments with resonances , this kind of
> thing :
>
> http://www.otsf.org/archaeoacoustics.html
>
> In this case a huge circular henge (3.5  m high banks)  180 m in diameter.

The acoustics of stonehenge (both original
and completed replicas) have been discussed
on the list previously.  If you are interested,
search the archives for:
Subject: Stonehenge's eerie sounds revived
Date: Fri, 27 Apr 2012

Subject: Gran Sasso - first impressions
Date: Mon, 18 Feb 2013

Regards,
Martin
-- 
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E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Acoustic properties of round rooms ?

[Paul Hodges]

How far off perfectly circular makes it not a problem?  I had no issues
when recording in the Union Chapel, Islington, and my mic was pretty
central (it was a concert in the round, though sadly before I could
record B-format).  

The latest offering on the "All of Bach" website (BWV 106) is also in
an essentially round chapel (but that's close mic'd).

Paul

-- 
Paul Hodges

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Re: [Sursound] Acoustic properties of round rooms ?

[David Pickett]

I thought at first of the membrane analysis, which of course involves 
Bessel functions, and which has been fully analysed in the text 
books.  There is, however, surely a difference between a circular 
membrane contrained at the edges (and even sometimes elsewhere) and 
air, which consists of independent and unattached molecules, though 
their motiion is constrained at the walls -- and this is the only 
thin in common with the molecules in a membrane.  Membrane behaviour 
must be different.  The vibrations of the air that get reflected from 
the walls are not up and down, as in the membrane motion, but in 
horizontal directions.  I continue to expect that there is an 
"infinite" number of modes, all at the same frequencies, due to the 
diameter being the same in all directions on the horizontal plane -- 
assuming we have a perfectly cylindrical room.


I visualize this by starting with the four walls or a square 
room.  There will be two similar horizontal sets of modes at the same 
frequencies.  Now make it octagonal and there are four sets of modes 
at the same frequencies.  Keep doing this and in the limit you arrive 
at a circular wall with an "infinite" number of modes...  Of course, 
there is some friction, but the effect would surely still be to have 
greater response at certain frequencies and not much in between them.


I would look to see if any work has been done on the behaviour of 
comparable frequency transveres radio waves in circular waveguide.


David


At 12:48 06-03-16, Augustine Leudar wrote:
>Im actually working on a sound installation which is involved with acoustic
>archeology in which Im hoping to experiments with resonances , this kind of
>thing :
>
>http://www.otsf.org/archaeoacoustics.html
>
>In this case a huge circular henge (3.5  m high banks)  180 m in diameter.
>
>https://en.wikipedia.org/wiki/Giant%27s_Ring
>
>Obviously with no roof resonance will not be as pronounced but there is
>still likely to be some sort of modal behaviour, especially if there had
>been many people singing/chanting etc . Apparently you cant work out modes
>for circular structures in the normal way by halving wavelength in relation
>to room dimensions etc  A family member of mine is a physicist and
>suggested this might be useful to work out modes for an open circular
>structure :
>
>https://en.wikipedia.org/wiki/Vibrations_of_a_circular_membrane#Animat
>ions_of_several_vibration_modes
>
>
>
>Then the following equation :
>
>Lowest frequency will be from longest wavelength which is 2 X pi X r/2.404
>(where r is radius of your circle) the next frequency has wavelength 2 pi
>r/3.83 = 1.64  x radius. And then 2 pi r/5.135 etc etc
>
>However this gives very long wavelengths - the highest mode is 11.61 there,
>but for me to calculate audible modes I would need numbers in this series
>above 150 or so (to get shorter audible wavelengths.
>Could anyone give numbers in the same series of numbers but above 150 ?
>
>
>
>
>
>
>
>
>On 5 March 2016 at 21:31, Martin Leese 
>wrote:
>
>> Augustine Leudar wrote:
>>
>> > Ive had a search online but cant really find much literature about this.
>> > Can anyone tell me anything about the acoustics of circular rooms/spaces
>> ?
>> > How to standing waves behave in circular spaces ?
>>
>> There was a discussion several years ago in
>> one of the rec.audio.* newsgroups on standing
>> waves in *spherical* rooms.  Unfortunately,
>> Google Groups has deleted all the older posts,
>> but this post might be it:
>> https://groups.google.com/forum/#!search/"spherical$20room"$20audio/
>> rec.audio.pro/hLCCrmlSFdw/Lq_80PhAZQ0J
>>
>> (In case the link does not work, I went to
>> groups.google.com and searched for:
>> "spherical room" audio
>> with the double quotes.)
>>
>> Regards,
>> Martin
>> --
>> Martin J Leese
>> E-mail: martin.leese  stanfordalumni.org
>> Web: http://members.tripod.com/martin_leese/
>> ___
>> Sursound mailing list
>> Sursound@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
>> edit account or options, view archives and so on.
>>
>
>
>
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Re: [Sursound] Acoustic properties of round rooms ?

[Augustine Leudar]

This study is interesting :

http://www.salford.ac.uk/computing-science-engineering/research/acoustics/architectural-and-building-acoustics/acoustics-of-stonehenge

Though obviously not a raised bank henge like the giants ring. Anyone else
know how I could work out the modes in the audible spectrum for this henge
(90 m radius) ?

On 6 March 2016 at 12:22, Bo-Erik Sandholm  wrote:

> In the forbidden city in Beijing there is 2 monuments that are round an
> have interesting acoustic properties.
>
> The first is a round marble covered area enclosed with a marble balustrade.
> When you stand in the centre an speak out loud you hear your own voice in a
> way you have not done before. You voice feel like it carries a long way.
> You feel like and emperor :-)
>
> The second is an round outside area enlosed with smooth walls, if you
> wisper close to the wall the sound of your voice is spread along the wall.
>
> BR Bo-Erik
> On 6 Mar 2016 12:53, "Dave Hunt"  wrote:
>
> > Hi,
> >
> > Such rooms tend to focus sound in various ways e.g the Whispering Gallery
> > in St Paul's Cathedral in London. Two people, widely spaced across the
> > diameter, can hold a quiet conversation which is inaudible to others at
> > different locations.
> >
> > I also have the impression that it becomes difficult to perceive the
> > locations of sounds from different sources in such spaces.
> >
> > Ciao,
> >
> > Dave Hunt
> >
> > On 5 Mar 2016, at 17:00, sursound-requ...@music.vt.edu wrote:
> >
> >>1. Acoustic properties of round rooms ? (Augustine Leudar)
> >>2. Re: Acoustic properties of round rooms ? (David Pickett)
> >>
> >> From: Augustine Leudar 
> >> Date: 5 March 2016 14:35:54 GMT
> >> To: Surround Sound discussion group 
> >> Subject: [Sursound] Acoustic properties of round rooms ?
> >>
> >>
> >> Ive had a search online but cant really find much literature about this.
> >> Can anyone tell me anything about the acoustics of circular
> rooms/spaces ?
> >> How to standing waves behave in circular spaces ?
> >>
> >> --
> >> www.augustineleudar.com
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> >> >
> >>
> >>
> >>
> >> From: David Pickett 
> >> Date: 5 March 2016 15:04:06 GMT
> >> To: Surround Sound discussion group 
> >> Subject: Re: [Sursound] Acoustic properties of round rooms ?
> >>
> >>
> >> At 15:35 05-03-16, Augustine Leudar wrote:
> >>
> >> >Ive had a search online but cant really find much literature about
> this.
> >> >Can anyone tell me anything about the acoustics of circular
> rooms/spaces
> >> ?
> >> >How to standing waves behave in circular spaces ?
> >>
> >> There is a strong standing wave at f = n/2D, where n = 1, 2, 3, 4, etc,
> >> and D is the diameter.  This is most apparent at the sweet spot in the
> >> centre!
> >>
> >> David
> >>
> >
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Re: [Sursound] Acoustic properties of round rooms ?

[Bo-Erik Sandholm]

In the forbidden city in Beijing there is 2 monuments that are round an
have interesting acoustic properties.

The first is a round marble covered area enclosed with a marble balustrade.
When you stand in the centre an speak out loud you hear your own voice in a
way you have not done before. You voice feel like it carries a long way.
You feel like and emperor :-)

The second is an round outside area enlosed with smooth walls, if you
wisper close to the wall the sound of your voice is spread along the wall.

BR Bo-Erik
On 6 Mar 2016 12:53, "Dave Hunt"  wrote:

> Hi,
>
> Such rooms tend to focus sound in various ways e.g the Whispering Gallery
> in St Paul's Cathedral in London. Two people, widely spaced across the
> diameter, can hold a quiet conversation which is inaudible to others at
> different locations.
>
> I also have the impression that it becomes difficult to perceive the
> locations of sounds from different sources in such spaces.
>
> Ciao,
>
> Dave Hunt
>
> On 5 Mar 2016, at 17:00, sursound-requ...@music.vt.edu wrote:
>
>>1. Acoustic properties of round rooms ? (Augustine Leudar)
>>2. Re: Acoustic properties of round rooms ? (David Pickett)
>>
>> From: Augustine Leudar 
>> Date: 5 March 2016 14:35:54 GMT
>> To: Surround Sound discussion group 
>> Subject: [Sursound] Acoustic properties of round rooms ?
>>
>>
>> Ive had a search online but cant really find much literature about this.
>> Can anyone tell me anything about the acoustics of circular rooms/spaces ?
>> How to standing waves behave in circular spaces ?
>>
>> --
>> www.augustineleudar.com
>> -- next part --
>> An HTML attachment was scrubbed...
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>> https://mail.music.vt.edu/mailman/private/sursound/attachments/20160305/8f39f7d0/attachment.html
>> >
>>
>>
>>
>> From: David Pickett 
>> Date: 5 March 2016 15:04:06 GMT
>> To: Surround Sound discussion group 
>> Subject: Re: [Sursound] Acoustic properties of round rooms ?
>>
>>
>> At 15:35 05-03-16, Augustine Leudar wrote:
>>
>> >Ive had a search online but cant really find much literature about this.
>> >Can anyone tell me anything about the acoustics of circular rooms/spaces
>> ?
>> >How to standing waves behave in circular spaces ?
>>
>> There is a strong standing wave at f = n/2D, where n = 1, 2, 3, 4, etc,
>> and D is the diameter.  This is most apparent at the sweet spot in the
>> centre!
>>
>> David
>>
>
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Re: [Sursound] Acoustic properties of round rooms ?

[Fons Adriaensen]

On Sun, Mar 06, 2016 at 11:48:05AM +, Augustine Leudar wrote:
 
> https://en.wikipedia.org/wiki/Giant%27s_Ring

Even if the walls were vertical and 100% reflective that would mean that
less than 2% of the acoustic power would be reflected back to the center.
This is not going to produce any modes at all.
 
> https://en.wikipedia.org/wiki/Vibrations_of_a_circular_membrane#Animations_of_several_vibration_modes
 
Wrong equation, there is no membrane in this case.

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: [Sursound] Acoustic properties of round rooms ?

[Dave Hunt]

Hi,

Such rooms tend to focus sound in various ways e.g the Whispering  
Gallery in St Paul's Cathedral in London. Two people, widely spaced  
across the diameter, can hold a quiet conversation which is inaudible  
to others at different locations.


I also have the impression that it becomes difficult to perceive the  
locations of sounds from different sources in such spaces.


Ciao,

Dave Hunt

On 5 Mar 2016, at 17:00, sursound-requ...@music.vt.edu wrote:

   1. Acoustic properties of round rooms ? (Augustine Leudar)
   2. Re: Acoustic properties of round rooms ? (David Pickett)

From: Augustine Leudar 
Date: 5 March 2016 14:35:54 GMT
To: Surround Sound discussion group 
Subject: [Sursound] Acoustic properties of round rooms ?


Ive had a search online but cant really find much literature about  
this.
Can anyone tell me anything about the acoustics of circular rooms/ 
spaces ?

How to standing waves behave in circular spaces ?

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From: David Pickett 
Date: 5 March 2016 15:04:06 GMT
To: Surround Sound discussion group 
Subject: Re: [Sursound] Acoustic properties of round rooms ?


At 15:35 05-03-16, Augustine Leudar wrote:

>Ive had a search online but cant really find much literature about  
this.
>Can anyone tell me anything about the acoustics of circular rooms/ 
spaces ?

>How to standing waves behave in circular spaces ?

There is a strong standing wave at f = n/2D, where n = 1, 2, 3, 4,  
etc, and D is the diameter.  This is most apparent at the sweet  
spot in the centre!


David


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Re: [Sursound] Acoustic properties of round rooms ?

[Augustine Leudar]

Im actually working on a sound installation which is involved with acoustic
archeology in which Im hoping to experiments with resonances , this kind of
thing :

http://www.otsf.org/archaeoacoustics.html

In this case a huge circular henge (3.5  m high banks)  180 m in diameter.

https://en.wikipedia.org/wiki/Giant%27s_Ring

Obviously with no roof resonance will not be as pronounced but there is
still likely to be some sort of modal behaviour, especially if there had
been many people singing/chanting etc . Apparently you cant work out modes
for circular structures in the normal way by halving wavelength in relation
to room dimensions etc  A family member of mine is a physicist and
suggested this might be useful to work out modes for an open circular
structure :

https://en.wikipedia.org/wiki/Vibrations_of_a_circular_membrane#Animations_of_several_vibration_modes



Then the following equation :

Lowest frequency will be from longest wavelength which is 2 X pi X r/2.404
(where r is radius of your circle) the next frequency has wavelength 2 pi
r/3.83 = 1.64  x radius. And then 2 pi r/5.135 etc etc

However this gives very long wavelengths - the highest mode is 11.61 there,
but for me to calculate audible modes I would need numbers in this series
above 150 or so (to get shorter audible wavelengths.
Could anyone give numbers in the same series of numbers but above 150 ?








On 5 March 2016 at 21:31, Martin Leese 
wrote:

> Augustine Leudar wrote:
>
> > Ive had a search online but cant really find much literature about this.
> > Can anyone tell me anything about the acoustics of circular rooms/spaces
> ?
> > How to standing waves behave in circular spaces ?
>
> There was a discussion several years ago in
> one of the rec.audio.* newsgroups on standing
> waves in *spherical* rooms.  Unfortunately,
> Google Groups has deleted all the older posts,
> but this post might be it:
> https://groups.google.com/forum/#!search/"spherical$20room"$20audio/
> rec.audio.pro/hLCCrmlSFdw/Lq_80PhAZQ0J
>
> (In case the link does not work, I went to
> groups.google.com and searched for:
> "spherical room" audio
> with the double quotes.)
>
> Regards,
> Martin
> --
> Martin J Leese
> E-mail: martin.leese  stanfordalumni.org
> Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Acoustic properties of round rooms ?

[Martin Leese]

Augustine Leudar wrote:

> Ive had a search online but cant really find much literature about this.
> Can anyone tell me anything about the acoustics of circular rooms/spaces ?
> How to standing waves behave in circular spaces ?

There was a discussion several years ago in
one of the rec.audio.* newsgroups on standing
waves in *spherical* rooms.  Unfortunately,
Google Groups has deleted all the older posts,
but this post might be it:
https://groups.google.com/forum/#!search/"spherical$20room"$20audio/rec.audio.pro/hLCCrmlSFdw/Lq_80PhAZQ0J

(In case the link does not work, I went to
groups.google.com and searched for:
"spherical room" audio
with the double quotes.)

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Acoustic properties of round rooms ?

[David Pickett]

At 15:35 05-03-16, Augustine Leudar wrote:

>Ive had a search online but cant really find much literature about this.
>Can anyone tell me anything about the acoustics of circular rooms/spaces ?
>How to standing waves behave in circular spaces ?

There is a strong standing wave at f = n/2D, where n = 1, 2, 3, 4, 
etc, and D is the diameter.  This is most apparent at the sweet spot 
in the centre!


David 


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