Reducing sound transmission to a mic....

[amdx]

 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs of
silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

 

[whit3rd]

On Saturday, August 13, 2022 at 5:47:27 PM UTC-7, amdx wrote:

Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
I want to sound isolate the Altoids tin from the upright extension it
will mount on.

Add mass to the microphone, let the soft rubber and mass keep it from
sonic-frequency acceleration. It might help to baffle the microphone\'s
port to the dish, so eddy currents in sidewinds don\'t move the diaphragm.

Your Altoids tin doesn\'t sit in FRONT of the microphone, so it doesn\'t really
flex and send sound waves that matter. Microphones, with low-mass
moving diaphragms, aren\'t accelerometer-sensitive.

 

[Anthony Stewart]

\".....On Saturday, 13 August 2022 at 20:47:27 UTC-4, amdx wrote:

Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.

The mounting is low pass with resonance with mass in damped springs for sonic attenuation and sub sonic position tracking. Old radio studio\'s used 4 corner springs undamped. Audio high gain will need to evaluation source of vibration and attenuation more carefully such as soft handle grips. Examine football remote mics.

 

[amdx]

On 8/13/2022 7:47 PM, amdx wrote:

 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?
                                     Mikek

 

[Liz Tuddenham]

amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?
                       Mikek

The BBC used to back their metal dishes with a thick layer of felt - in
particular this was to reduce the noise of raindrops hitting the dish
but it also reduced \'ringing\' of the metal. A number of patches of
bituminised roofing felt, stuck on with flexible solvent glue
(Evo-Stick), covering about 50% of the total area, should be enough to
deaden the ringing effect of your dish.

A wind cover for the mic needs to have a space between the outer
covering and the mic itself, otherwise wind penetrating the base layer
of the fur (or whatever you use) will produce a pressure change directly
on the diaphragm. With a decent gap, the penetrating air can circulate
gently and harmlessly. The easiest way to achive this is to use a large
conventional open foam \'pop\' shield covered with a furry sock - don\'t
rely on the sock alone.

[How to make one for a Tascam DR-05:
http://www.poppyrecords.co.uk/other/poileuse/poileuse.php
modify as required.]

--
~ Liz Tuddenham ~
(Remove the \".invalid\"s and add \".co.uk\" to reply)
www.poppyrecords.co.uk

 

[Liz Tuddenham]

amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.

Are you only hearing the low frequency component of the traffic noise?
A dish will give no directional effect at all at low frequencies.

If you want to produce a directional effect as low as (for example)
250c/s you will need a dish whose diameter is in the region of 4ft
diameter.

 

[Joe Gwinn]

On Sun, 14 Aug 2022 17:55:34 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?
                       Mikek

The BBC used to back their metal dishes with a thick layer of felt - in
particular this was to reduce the noise of raindrops hitting the dish
but it also reduced \'ringing\' of the metal. A number of patches of
bituminised roofing felt, stuck on with flexible solvent glue
(Evo-Stick), covering about 50% of the total area, should be enough to
deaden the ringing effect of your dish.

This has almost achieved a constrained-layer damper, which would be a
large improvement. Just glue an outer metal foil layer, so the
tar-felt is in the middle.

..<https://en.wikipedia.org/wiki/Constrained-layer_damping>

The linked masters thesis has much detail, and is open.

..<https://vtechworks.lib.vt.edu/handle/10919/35350>

\"Passive Viscoelastic Constrained Layer Damping Application for a
Small Aircraft Landing Gear System\"

Joe Gwinn

 

[amdx]

On 8/14/2022 1:03 PM, Joe Gwinn wrote:

On Sun, 14 Aug 2022 17:55:34 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek
  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?
                       Mikek
The BBC used to back their metal dishes with a thick layer of felt - in
particular this was to reduce the noise of raindrops hitting the dish
but it also reduced \'ringing\' of the metal. A number of patches of
bituminised roofing felt, stuck on with flexible solvent glue
(Evo-Stick), covering about 50% of the total area, should be enough to
deaden the ringing effect of your dish.

This has almost achieved a constrained-layer damper, which would be a
large improvement. Just glue an outer metal foil layer, so the
tar-felt is in the middle.

.<https://en.wikipedia.org/wiki/Constrained-layer_damping

The linked masters thesis has much detail, and is open.

.<https://vtechworks.lib.vt.edu/handle/10919/35350

\"Passive Viscoelastic Constrained Layer Damping Application for a
Small Aircraft Landing Gear System\"

Joe Gwinn

That\'s interesting, I have couple of tar like substances on a substrate.
Peal and stick for roofs. And also a thicker 6\" wide sealing tape.
 If I get energetic I\'ll set my phone sinewave generator off axis at 1000Hz
and measure, then apply and measure again to see if it cuts it down.
                       Thanks, Mikek

 

[Don Y]

On 8/14/2022 9:40 AM, amdx wrote:

I got all working and found I hear the traffic so loud that I can\'t raise the
gain high even off axis.

Think of the geometry involved. The sounds you are (presumably) interested in
are (more or less) \"behind\" the dish-facing microphone. You can recess the
microphone in a \"cup\" that works to attenuate sources coming in from the side
but not interfering with the reflected sounds being FOCUSED on the microphone.
The dimensions of that cup depend on the size of the dish and how much you want
to \"select\".

You will always hear the undesirable sounds. What you are hoping to do
is amplify the sounds you are focused on.

The whispering gallery at the Museum of Science and Industry illustrates this
dramatically.

<https://www.msichicago.org/explore/whats-here/exhibits/whispering-gallery/>

Standing at a focus, you can clearly hear those folks around you -- at NORMAL
volume levels. The \"magic\" comes from the fact that you can hear the
speaker at the far (30 ft?) focus WHISPERING just as clearly.

[Amusing to see math actually work, eh? Similar issues in the design of
theatrical lighting...]

Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions and
re-radiates though the air to the mic.
I\'m thinking the commercial poly-carbonate parabolic dishes do less of this,
but it is a question.

Is there a material that will vibrate less from ambient sound and be highly
reflective?

 

[amdx]

On 8/14/2022 1:54 PM, Don Y wrote:

On 8/14/2022 9:40 AM, amdx wrote:
   I got all working and found I hear the traffic so loud that I
can\'t raise the
gain high even off axis.

Think of the geometry involved.  The sounds you are (presumably)
interested in
are (more or less) \"behind\" the dish-facing microphone.  You can
recess the microphone in a \"cup\" that works to attenuate sources
coming in from the side
but not interfering with the reflected sounds being FOCUSED on the
microphone.
The dimensions of that cup depend on the size of the dish and how much
you want
to \"select\".

You will always hear the undesirable sounds.  What you are hoping to do
is amplify the sounds you are focused on.

The whispering gallery at the Museum of Science and Industry
illustrates this
dramatically.

https://www.msichicago.org/explore/whats-here/exhibits/whispering-gallery/


Standing at a focus, you can clearly hear those folks around you -- at
NORMAL
volume levels.  The \"magic\" comes from the fact that you can hear the
speaker at the far (30 ft?) focus WHISPERING just as clearly.

[Amusing to see math actually work, eh?  Similar issues in the design of
theatrical lighting...]


  Here is my working theory and please counter it if you know better.
  The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
  I\'m thinking the commercial poly-carbonate parabolic dishes do less
of this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?

I\'m looking at some cheap ABS reflectors, the may be shape in question.
How much does that matter?
All Amazon Links, some very long so I tinyurled them.
 Your opinion on what may work best. Thanks, Mikek

Here\'s a 16\", a little flat at the center.
> https://www.amazon.com/Perky-Pet-340-Transparent-16-Inch-Squirrel/dp/B0006G52ME/ref=sr_1_6?keywords=squirrel+baffle+plastic&qid=1660504956&sr=8-6

Here is a 12\", it has a constant shape.
> https://tinyurl.com/2b9vknvp

Here is a 13\" with extended sides, That may put the mic within the
edges, that might be a good thing.

And a 10\".
> https://tinyurl.com/427w4nxr

 

[Don Y]

On 8/14/2022 12:55 PM, amdx wrote:

On 8/14/2022 1:54 PM, Don Y wrote:
On 8/14/2022 9:40 AM, amdx wrote:
I got all working and found I hear the traffic so loud that I can\'t raise
the
gain high even off axis.

Think of the geometry involved. The sounds you are (presumably) interested in
are (more or less) \"behind\" the dish-facing microphone. You can recess the
microphone in a \"cup\" that works to attenuate sources coming in from the side
but not interfering with the reflected sounds being FOCUSED on the microphone.
The dimensions of that cup depend on the size of the dish and how much you want
to \"select\".

You will always hear the undesirable sounds. What you are hoping to do
is amplify the sounds you are focused on.

The whispering gallery at the Museum of Science and Industry illustrates this
dramatically.

https://www.msichicago.org/explore/whats-here/exhibits/whispering-gallery/

Standing at a focus, you can clearly hear those folks around you -- at NORMAL
volume levels. The \"magic\" comes from the fact that you can hear the
speaker at the far (30 ft?) focus WHISPERING just as clearly.

[Amusing to see math actually work, eh? Similar issues in the design of
theatrical lighting...]


Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions and
re-radiates though the air to the mic.
I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be highly
reflective?

I\'m looking at some cheap ABS reflectors, the may be shape in question. How
much does that matter?

<shrug> There are lots of factors that will influence the overall result.
And, this isn\'t my field of expertise.

I\'d go to the nearest \"dollar store\" and pick up some cheap plastic
cups/bowls and try them on for size. Something sturdier than a
tupperware container. A file can make quick work of \"adjusting\" its
size. (and, at < $1/each, you can afford to experiment)

Draw a parabola (or find an online image). Notice the paths the
distant rays follow to the focus. The deeper the cup, the more
the peripheral rays are excluded (the less \"collector area\"
comes to your aid). If your dish is fairly \"flat\" (focus
well above the sides of the dish), then those peripheral rays
are already not being caught -- so you can afford a deeper cup.

OTOH, a deeper dish (focus closer to the dish than the outermost edge)
means there is a benefit to those peripheral rays. And, also less
need to shield the side of the microphone as the \"high walls\" of the
dish are already doing some of that for you.

Notice how shallow/small the reflector in the Whispering Gallery.
The listener FACES the clear reflector, his back to the other
listener\'s back. His ears relatively exposed to people walking
past him. But, very little *gain* from those sound sources.

I think the biggest win (for a portable mic) comes from having a deep
parabola for your dish -- so the focus is more \"shielded\" from sound/wind
blowing across the microphone. Maximize gain for the \"sought signal\"
and hope the ambient doesn\'t overwhelm.

Play. It\'s a fun project. Little chance of injury, damage, etc.
The dish is the most precious item -- and I suspect you can find
several of them listed on CL if you were really interested (or,
neighbors who are no longer using theirs)

I did this when a kid. But, the sounds I was after were distant with
few other sound sources competing. E.g., listening to things off in
the woods or across a field. I didn\'t discover cars and traffic until
much later in life :<

All Amazon Links, some very long so I tinyurled them.
Your opinion on what may work best. Thanks, Mikek

Here\'s a 16\", a little flat at the center.
https://www.amazon.com/Perky-Pet-340-Transparent-16-Inch-Squirrel/dp/B0006G52ME/ref=sr_1_6?keywords=squirrel+baffle+plastic&qid=1660504956&sr=8-6


Here is a 12\", it has a constant shape.
https://tinyurl.com/2b9vknvp

Here is a 13\" with extended sides, That may put the mic within the edges, that
might be a good thing.

And a 10\".
https://tinyurl.com/427w4nxr

 

[amdx]

On 8/14/2022 3:33 PM, Don Y wrote:

On 8/14/2022 12:55 PM, amdx wrote:
On 8/14/2022 1:54 PM, Don Y wrote:
On 8/14/2022 9:40 AM, amdx wrote:
   I got all working and found I hear the traffic so loud that I
can\'t raise the
gain high even off axis.

Think of the geometry involved.  The sounds you are (presumably)
interested in
are (more or less) \"behind\" the dish-facing microphone.  You can
recess the microphone in a \"cup\" that works to attenuate sources
coming in from the side
but not interfering with the reflected sounds being FOCUSED on the
microphone.
The dimensions of that cup depend on the size of the dish and how
much you want
to \"select\".

You will always hear the undesirable sounds.  What you are hoping to do
is amplify the sounds you are focused on.

The whispering gallery at the Museum of Science and Industry
illustrates this
dramatically.

https://www.msichicago.org/explore/whats-here/exhibits/whispering-gallery/


Standing at a focus, you can clearly hear those folks around you --
at NORMAL
volume levels.  The \"magic\" comes from the fact that you can hear the
speaker at the far (30 ft?) focus WHISPERING just as clearly.

[Amusing to see math actually work, eh?  Similar issues in the
design of
theatrical lighting...]


  Here is my working theory and please counter it if you know better.
  The metal satellite dish picks up ambient sound from all
directions and re-radiates though the air to the mic.
  I\'m thinking the commercial poly-carbonate parabolic dishes do
less of this, but it is a question.

Is there a material that will vibrate less from ambient sound and
be highly reflective?

I\'m looking at some cheap ABS reflectors, the may be shape in
question. How much does that matter?

shrug>  There are lots of factors that will influence the overall
result.
And, this isn\'t my field of expertise.

I\'d go to the nearest \"dollar store\" and pick up some cheap plastic
cups/bowls and try them on for size.  Something sturdier than a
tupperware container.  A file can make quick work of \"adjusting\" its
size.  (and, at < $1/each, you can afford to experiment)

Draw a parabola (or find an online image).  Notice the paths the
distant rays follow to the focus.  The deeper the cup, the more
the peripheral rays are excluded (the less \"collector area\"
comes to your aid).  If your dish is fairly \"flat\" (focus
well above the sides of the dish), then those peripheral rays
are already not being caught -- so you can afford a deeper cup.

OTOH, a deeper dish (focus closer to the dish than the outermost edge)
means there is a benefit to those peripheral rays.  And, also less
need to shield the side of the microphone as the \"high walls\" of the
dish are already doing some of that for you.

Notice how shallow/small the reflector in the Whispering Gallery.
The listener FACES the clear reflector, his back to the other
listener\'s back.  His ears relatively exposed to people walking
past him.  But, very little *gain* from those sound sources.

I think the biggest win (for a portable mic) comes from having a deep
parabola for your dish -- so the focus is more \"shielded\" from sound/wind
blowing across the microphone.  Maximize gain for the \"sought signal\"
and hope the ambient doesn\'t overwhelm.

Play.  It\'s a fun project.  Little chance of injury, damage, etc.
The dish is the most precious item -- and I suspect you can find
several of them listed on CL if you were really interested (or,
neighbors who are no longer using theirs)

I did this when a kid.  But, the sounds I was after were distant with
few other sound sources competing.  E.g., listening to things off in
the woods or across a field.  I didn\'t discover cars and traffic until
much later in life  :

All Amazon Links, some very long so I tinyurled them.
  Your opinion on what may work best. Thanks, Mikek

Here\'s a 16\", a little flat at the center.
https://www.amazon.com/Perky-Pet-340-Transparent-16-Inch-Squirrel/dp/B0006G52ME/ref=sr_1_6?keywords=squirrel+baffle+plastic&qid=1660504956&sr=8-6


Here is a 12\", it has a constant shape.
https://tinyurl.com/2b9vknvp

Here is a 13\" with extended sides, That may put the mic within the
edges, that might be a good thing.

And a 10\".
https://tinyurl.com/427w4nxr


Oh, I see I missed the link for the extended side reflector.
https://www.amazon.com/Myard-Wobbly-Squirrel-Baffle-Deflector/dp/B07HCCX5D6/ref=sr_1_30?crid=35IAGKWXKWQJB&keywords=squirrel+baffle+plastic&qid=1660505201&sprefix=%2Caps%2C387&sr=8-30

For those that didn\'t want to click all the lengths, I put all 4 shapes
in on picture and put it on drop box.
> https://www.dropbox.com/s/zxaspkx9m92bbxc/Shape%201.jpg?dl=0

                               Mikek

 

[Jan Panteltje]

On a sunny day (Sun, 14 Aug 2022 14:55:39 -0500) it happened amdx
<amdx@knology.net> wrote in <tdbjvu$38g2f$1@dont-email.me>:

  Here is my working theory and please counter it if you know better.
  The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
  I\'m thinking the commercial poly-carbonate parabolic dishes do less
of this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?

The thread about laser range findings recalled the discussions about
using the time variations from a laser reflected from a window to monitor audio in a room.
(from vibrating glass)

If you could point it at somebodies throat and pick up sound like old throat mikes....
Maybe the red spot would freak them out...
Use IR perhaps.. camera for pointing, could be a fun project.
Or point at something in the vicinity, cardboard boxes, screens, what not.

Its old tech that could be taken as start point for a better spy system.

 

[Jasen Betts]

On 2022-08-14, amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek

  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.

If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?

Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

--
Jasen.

 

[amdx]

On 8/15/2022 5:59 AM, Jasen Betts wrote:

On 2022-08-14, amdx <amdx@knology.net> wrote:
On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek
  I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
 Here is my working theory and please counter it if you know better.
 The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

 I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.
Is there a material that will vibrate less from ambient sound and be
highly reflective?
Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

In early testing of noise from a couple different pre amps, I surrounded
my mic
in a sheet of lead rolled into a tube with sealed ends. This worked very
well!
This eliminated traffic noise that I could hear through the headphones
while inside my house.
I wonder if I could roll a cone of lead to shield the mic from some of
the off axis ambient noise?
                                             Mikek

 

[a a]

On Monday, 15 August 2022 at 13:55:26 UTC+2, amdx wrote:

On 8/15/2022 5:59 AM, Jasen Betts wrote:
On 2022-08-14, amdx <am...@knology.net> wrote:
On 8/13/2022 7:47 PM, amdx wrote:
Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

Mikek
I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.
Is there a material that will vibrate less from ambient sound and be
highly reflective?
Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

In early testing of noise from a couple different pre amps, I surrounded
my mic
in a sheet of lead rolled into a tube with sealed ends. This worked very
well!
This eliminated traffic noise that I could hear through the headphones
while inside my house.
I wonder if I could roll a cone of lead to shield the mic from some of
the off axis ambient noise?
Mikek
have you tried 4 mics background noise filtering out concept known from Kinect

https://qph.cf2.quoracdn.net/main-qimg-3a6efb532cf8ce709a3f14c8b96b3661-pjlq

How does Microsoft\'s Kinect work from a technology standpoint?

https://www.quora.com/How-does-Microsofts-Kinect-work-from-a-technology-standpoint

 

[John Walliker]

On Monday, 15 August 2022 at 12:55:26 UTC+1, amdx wrote:

On 8/15/2022 5:59 AM, Jasen Betts wrote:
On 2022-08-14, amdx <am...@knology.net> wrote:
On 8/13/2022 7:47 PM, amdx wrote:
Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

Mikek
I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.
Is there a material that will vibrate less from ambient sound and be
highly reflective?
Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

In early testing of noise from a couple different pre amps, I surrounded
my mic
in a sheet of lead rolled into a tube with sealed ends. This worked very
well!
This eliminated traffic noise that I could hear through the headphones
while inside my house.
I wonder if I could roll a cone of lead to shield the mic from some of
the off axis ambient noise?
Mikek

That will only help at high frequencies. Are you still using an omni-directional mic?
You might get better results if you use a mic with a cardioid response and point the
most sensitive direction at the dish.
John

 

[Ricky]

On Monday, August 15, 2022 at 7:55:26 AM UTC-4, amdx wrote:

On 8/15/2022 5:59 AM, Jasen Betts wrote:
On 2022-08-14, amdx <am...@knology.net> wrote:
On 8/13/2022 7:47 PM, amdx wrote:
Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

Mikek
I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.
Is there a material that will vibrate less from ambient sound and be
highly reflective?
Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

In early testing of noise from a couple different pre amps, I surrounded
my mic
in a sheet of lead rolled into a tube with sealed ends. This worked very
well!
This eliminated traffic noise that I could hear through the headphones
while inside my house.
I wonder if I could roll a cone of lead to shield the mic from some of
the off axis ambient noise?
Mikek

I think the way parabolic mics work is to overwhelm the stray noise with the gain of the on axis sounds. If you are still hearing ambient noise you can try a bigger reflector. Remember, the area of the reflector goes up with the square of the diameter.

You can also filter the lower frequencies since they are not important to many uses.

In sonar work, they use what is called beam forming. This involves the use of many microphones and signal processing, to reduce the amplitude of signals arriving off axis. This can easily eliminate sounds from any direction, including from the rear of the sensor array. If you don\'t need for it to be mobile, it can work at any frequency range you want. Picture a four foot square sheet of thin plywood, with tiny, electret mics on a 2 inch grid, or 24^2 or 576 mics. Wow! That\'s a lot of microphones! I guess that\'s why submarine sonar systems cost so much!
Anyway, each mic would need a small amp with band pass filtering and an ADC input. They have ADCs with up to 16 inputs each.

The spacing of the mics set the highest frequency in use and the aggregate size sets the lowest frequency. The numbers I picked were for the full range of speech, 300 Hz to 3,300 Hz. The number of sensors can be reduced by changing these numbers. It might be possible to make the array 1 dimensional if aiming vertically is not important. That would reduce your mic count a lot.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[John Walliker]

On Monday, 15 August 2022 at 18:05:01 UTC+1, Ricky wrote:

On Monday, August 15, 2022 at 7:55:26 AM UTC-4, amdx wrote:
On 8/15/2022 5:59 AM, Jasen Betts wrote:
On 2022-08-14, amdx <am...@knology.net> wrote:
On 8/13/2022 7:47 PM, amdx wrote:
Mounting a mic at the focus of a satellite dish want.
I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
I want to sound isolate the Altoids tin from the upright extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

Mikek
I got all working and found I hear the traffic so loud that I can\'t
raise the
gain high even off axis.
Here is my working theory and please counter it if you know better.
The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
If it\'s ringing the sound waves won\'t be normal to the dish but at
some angle determined by the wave propogation speed ratios.
also most of the dish is not normal to the microphone, but much of it
is probably close enough.

I\'m thinking the commercial poly-carbonate parabolic dishes do less of
this, but it is a question.
Is there a material that will vibrate less from ambient sound and be
highly reflective?
Steel satellite dish with sound deadening material (from automiobile parts shop)
stuck on the back, or the nucelar option: concrete (as thick as you care to make it)

In early testing of noise from a couple different pre amps, I surrounded
my mic
in a sheet of lead rolled into a tube with sealed ends. This worked very
well!
This eliminated traffic noise that I could hear through the headphones
while inside my house.
I wonder if I could roll a cone of lead to shield the mic from some of
the off axis ambient noise?
Mikek
I think the way parabolic mics work is to overwhelm the stray noise with the gain of the on axis sounds. If you are still hearing ambient noise you can try a bigger reflector. Remember, the area of the reflector goes up with the square of the diameter.

You can also filter the lower frequencies since they are not important to many uses.

In sonar work, they use what is called beam forming. This involves the use of many microphones and signal processing, to reduce the amplitude of signals arriving off axis. This can easily eliminate sounds from any direction, including from the rear of the sensor array. If you don\'t need for it to be mobile, it can work at any frequency range you want. Picture a four foot square sheet of thin plywood, with tiny, electret mics on a 2 inch grid, or 24^2 or 576 mics. Wow! That\'s a lot of microphones! I guess that\'s why submarine sonar systems cost so much!
Anyway, each mic would need a small amp with band pass filtering and an ADC input. They have ADCs with up to 16 inputs each.

The spacing of the mics set the highest frequency in use and the aggregate size sets the lowest frequency. The numbers I picked were for the full range of speech, 300 Hz to 3,300 Hz. The number of sensors can be reduced by changing these numbers. It might be possible to make the array 1 dimensional if aiming vertically is not important. That would reduce your mic count a lot.

Here is a paper from 1976 on the subject:
https://www.sciencedirect.com/science/article/abs/pii/0022460X76905526

John

 

[Martin Brown]

On 14/08/2022 19:35, amdx wrote:

On 8/14/2022 1:03 PM, Joe Gwinn wrote:
On Sun, 14 Aug 2022 17:55:34 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

amdx <amdx@knology.net> wrote:

On 8/13/2022 7:47 PM, amdx wrote:
 Mounting a mic at the focus of a satellite dish want.
 I have a mic connected to an Altoids tin, I have the mic mounted in
soft rubber.
The tin will be mounted to an upright extension that is mounted to the
normal extended arm on a satellite dish.
 I want to sound isolate the Altoids tin from the upright
extension it
will mount on.
Does silicone have low sound transmission? I\'m thinking about 4 dabs
of silicone about 1/4\" tall,
in the corners on the underside of the Altoid tin.

Does low sound transmission mean the same as high dampening?

                           Mikek
    I got all working and found I hear the traffic so loud that I
can\'t
raise the
gain high even off axis.
   Here is my working theory and please counter it if you know better.
   The metal satellite dish picks up ambient sound from all directions
and re-radiates though the air to the mic.
   I\'m thinking the commercial poly-carbonate parabolic dishes do
less of
this, but it is a question.

Is there a material that will vibrate less from ambient sound and be
highly reflective?
                         Mikek
The BBC used to back their metal dishes with a thick layer of felt - in
particular this was to reduce the noise of raindrops hitting the dish
but it also reduced \'ringing\' of the metal.  A number of patches of
bituminised roofing felt, stuck on with flexible solvent glue
(Evo-Stick), covering about 50% of the total area, should be enough to
deaden the ringing effect of your dish.

This has almost achieved a constrained-layer damper, which would be a
large improvement.  Just glue an outer metal foil layer, so the
tar-felt is in the middle.

.<https://en.wikipedia.org/wiki/Constrained-layer_damping

The linked masters thesis has much detail, and is open.

.<https://vtechworks.lib.vt.edu/handle/10919/35350

\"Passive Viscoelastic Constrained Layer Damping Application for a
Small Aircraft Landing Gear System\"

Joe Gwinn
That\'s interesting, I have couple of tar like substances on a substrate.
Peal and stick for roofs. And also a thicker 6\" wide sealing tape.
 If I get energetic I\'ll set my phone sinewave generator off axis at
1000Hz
and measure, then apply and measure again to see if it cuts it down.
                       Thanks, Mikek

The stuff you want to back the reflector with is an acoustic foam sold
in small pieces for making PCs much quieter and in large pieces for
recording studios. It is essentially a moderately dense flexible foam
with a thin slab of rubber in the middle. The latter absorbs most of the
coherent sound energy and the foam then dissipates it. Metal boxes and
sheets that would otherwise ring like a bell can be almost completely
silenced by applying it.

Silicone gaskets in just the right places can help a lot too.

There is always a trade off between weight and effectiveness. The
commercial products intended for acoustic management are very close to
optimal since it is their business to be effective in minimal space.

--
Regards,
Martin Brown