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Microphone risk factors

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  Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-10 21:27 -0700
    Re: Microphone risk factors Phil Allison <pallison49@gmail.com> - 2017-05-10 21:39 -0700
    Re: Microphone risk factors jrwalliker@gmail.com - 2017-05-11 07:01 -0700
      Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-11 11:06 -0700
        Re: Microphone risk factors piglet <erichpwagner@hotmail.com> - 2017-05-12 09:02 +0100
        Re: Microphone risk factors "Michael Kellett" <nospam@invalid.com> - 2017-05-12 16:02 +0100
          Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-12 09:37 -0700
            Re: Microphone risk factors "Michael Kellett" <nospam@invalid.com> - 2017-05-12 18:08 +0100
              Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-12 11:02 -0700
                Re: Microphone risk factors Phil Allison <pallison49@gmail.com> - 2017-05-12 17:44 -0700
                Re: Microphone risk factors Terry Newton <nbill@bellsouth.net> - 2017-05-13 17:19 +0000
                  Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-13 11:57 -0700
                    Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-13 19:12 +0000
                      Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 08:40 +0000
                      Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 09:17 +0000
                        Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 10:49 +0000
                    Re: Microphone risk factors Terry Newton <nbill@bellsouth.net> - 2017-05-13 19:26 +0000
                      Re: Microphone risk factors (OT -- long) Don Y <blockedofcourse@foo.invalid> - 2017-05-13 13:37 -0700
              Re: Microphone risk factors "dcaster@krl.org" <dcaster@krl.org> - 2017-05-13 11:06 -0700
                Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-13 12:11 -0700
                Re: Microphone risk factors krw@notreal.com - 2017-05-13 20:36 -0400

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#459872 — Microphone risk factors

"Average" quality -- cost and size being more significant criteria.
(Think in terms of cell phones quality/cost/size)

What sorts of issues affect reliability, failure modes, etc.?

Any advantages to one technology over another?  Any issues
specifically related to MEMS devices?

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#459874

Don Y wrote:
-----------


** Here we go again - another fucking stupid troll from Don Y. 

 Totally without context of any sort plus an irrelevant heading. 

 Hey Don: 

 The net is flooded with info about all kinds of microphones.

 Go look some of it up yourself you lazy shit. 





....  Phil 

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#459902

On Thursday, 11 May 2017 05:27:32 UTC+1, Don Y  wrote:
> "Average" quality -- cost and size being more significant criteria.
> (Think in terms of cell phones quality/cost/size)
> 
> What sorts of issues affect reliability, failure modes, etc.?
> 
> Any advantages to one technology over another?  Any issues
> specifically related to MEMS devices?

Noise floor is generally higher than electrets, but they are not
significantly affected by high temperatures and humidity.

MEMS devices can often be reflow soldered.  Electrets would
depolarize if heated to such temperatures.

John

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#459918

On 5/11/2017 7:01 AM, jrwalliker@gmail.com wrote:
> On Thursday, 11 May 2017 05:27:32 UTC+1, Don Y  wrote:
>> "Average" quality -- cost and size being more significant criteria.
>> (Think in terms of cell phones quality/cost/size)
>>
>> What sorts of issues affect reliability, failure modes, etc.?
>>
>> Any advantages to one technology over another?  Any issues
>> specifically related to MEMS devices?
>
> Noise floor is generally higher than electrets, but they are not
> significantly affected by high temperatures and humidity.

I spent ~5 hours at a buddy's studio, yesterday.  As expected,
he could tell me why he mic's the top hat with a different
microphone than the kicker or the sax -- or the lead vocalist.
And, what "justifies" the differences in costs.

But, it was virtually impossible to push him off the "recording
music" application to think of the microphone as a "audio frequency
sound pressure/vibration transducer".

E.g., when I asked him how he might *alter* his selection of
microphones (assume still recording a particular artist/group)
to do so OUTSIDE IN THE RAIN, he quickly fell behind the
avoidance of "the band wouldn't want to PERFORM in the rain,
let alone sit for a studio session in it!"  I.e., he's too wed
to the idea of human beings as being the source of the sounds
he's capturing.  So, assumes the environment is OBVIOUSLY going
to be acceptable for COMFORTABLE human occupation (e.g., "STP").

     "Lets assume a group *wanted* to be recorded in the rain.  Are
     there any microphones you'd AVOID *using* in that environment?
     And, if so, why -- would they just perform poorly?  Or, would
     they risk being irreversibly damaged?"

     "If I wasn't planning on *using* them in the rain, but they
     happened to be left on an outdoor table/bench and it suddenly
     rained *on* them -- which would you regret most?"

     "If the rain had broken but the air was still really humid,
     how does that affect the above?"

He finally offered that condenser mic's tend not to like humidity
but that the effect is on performance and is temporary -- dry out
the microphone (carefully!) and its no worse for the wear (though
I suspect he doesn't REALLY believe this as he seemed hesitant
to want to find himself in that situation!)

Rephrase the question with temperature:  could I use these to
record the sounds on the Antartic tundra?  as its really cold,
I probably wouldn't want to hang around while capturing those
sounds -- could I leave the microphone set up for a month
if I protected it from precipitation?  would it see restored
joy when it was finally warmed back up?

What if I *fastened* it to the underside of that cow bell so
every time the bell was struck, *it* was (effectively) struck,
even if indirectly?

What if I fastened a pair of them to the heads in my car and
used them to monitor rocker arm/lifter noise?  Would they
be upset with the prolonged exposure to the heat of the
engine compartment?  Which technology would be LEAST upset?

> MEMS devices can often be reflow soldered.  Electrets would
> depolarize if heated to such temperatures.

He had nothing to offer on MEMS -- probably because it doesn't
offer the predictable (as in "traditionally known") performance
of the more established technologies.  It would *seem* that it
should be relatively durable.  Yet, its not widely employed in the
sorts of things that you might expect to find it due to its
small size and level of integration.  E.g., I think most (?) cell
phones use electret condensers (though I haven't taken many
*different* makes/models apart to see how pervasive that claim).

What are the *downsides* of MEMS units?

What I'm looking for are guidelines that might be common to all
such "transducers" with *specific* refinements that would
apply to different technologies.  Most of the information I've
found specifies those refinements in terms of cost or
*signal* characteristics (use this for lots of dynamic range
in signal; use that for a flat response; etc.)

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#459964

On 11/05/2017 19:06, Don Y wrote:
> He finally offered that condenser mic's tend not to like humidity
> but that the effect is on performance and is temporary -- dry out
> the microphone (carefully!) and its no worse for the wear (though
> I suspect he doesn't REALLY believe this as he seemed hesitant
> to want to find himself in that situation!)
>

The majority of condenser mic's use extrememly high impedance circuitry, 
even gigaohm resistors, so humidity is a problem. Low impedance RF based 
models exist and are favoured by outdoor wildlife and location sound 
people. Half an hour web browsing would be informative :)

Mobile phones now use MEM mics but I am not aware of "serious" 
audiophilic users of MEMs but I am not up to date. MEMs diaphragm 
capture area is very small.

piglet

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#459978

Don Y:
> On 5/11/2017 7:01 AM, jrwalliker@gmail.com wrote:
>> On Thursday, 11 May 2017 05:27:32 UTC+1, Don Y  wrote:
>>> "Average" quality -- cost and size being more significant criteria.
>>> (Think in terms of cell phones quality/cost/size)
>>>
>>> What sorts of issues affect reliability, failure modes, etc.?
>>>
>>> Any advantages to one technology over another?  Any issues
>>> specifically related to MEMS devices?
>>
>> Noise floor is generally higher than electrets, but they are not
>> significantly affected by high temperatures and humidity.
> 
> I spent ~5 hours at a buddy's studio, yesterday.  As expected,
> he could tell me why he mic's the top hat with a different
> microphone than the kicker or the sax -- or the lead vocalist.
> And, what "justifies" the differences in costs.
> 



> But, it was virtually impossible to push him off the "recording
> music" application to think of the microphone as a "audio frequency
> sound pressure/vibration transducer".
> 
> E.g., when I asked him how he might *alter* his selection of
> microphones (assume still recording a particular artist/group)
> to do so OUTSIDE IN THE RAIN, he quickly fell behind the
> avoidance of "the band wouldn't want to PERFORM in the rain,
> let alone sit for a studio session in it!"  I.e., he's too wed
> to the idea of human beings as being the source of the sounds
> he's capturing.  So, assumes the environment is OBVIOUSLY going
> to be acceptable for COMFORTABLE human occupation (e.g., "STP").
> 
>      "Lets assume a group *wanted* to be recorded in the rain.  Are
>      there any microphones you'd AVOID *using* in that environment?
>      And, if so, why -- would they just perform poorly?  Or, would
>      they risk being irreversibly damaged?"
> 
>      "If I wasn't planning on *using* them in the rain, but they
>      happened to be left on an outdoor table/bench and it suddenly
>      rained *on* them -- which would you regret most?"
> 
>      "If the rain had broken but the air was still really humid,
>      how does that affect the above?"
> 
> He finally offered that condenser mic's tend not to like humidity
> but that the effect is on performance and is temporary -- dry out
> the microphone (carefully!) and its no worse for the wear (though
> I suspect he doesn't REALLY believe this as he seemed hesitant
> to want to find himself in that situation!)
> 
> Rephrase the question with temperature:  could I use these to
> record the sounds on the Antartic tundra?  as its really cold,
> I probably wouldn't want to hang around while capturing those
> sounds -- could I leave the microphone set up for a month
> if I protected it from precipitation?  would it see restored
> joy when it was finally warmed back up?
> 
> What if I *fastened* it to the underside of that cow bell so
> every time the bell was struck, *it* was (effectively) struck,
> even if indirectly?
> 
> What if I fastened a pair of them to the heads in my car and
> used them to monitor rocker arm/lifter noise?  Would they
> be upset with the prolonged exposure to the heat of the
> engine compartment?  Which technology would be LEAST upset?
> 
>> MEMS devices can often be reflow soldered.  Electrets would
>> depolarize if heated to such temperatures.
> 
> He had nothing to offer on MEMS -- probably because it doesn't
> offer the predictable (as in "traditionally known") performance
> of the more established technologies.  It would *seem* that it
> should be relatively durable.  Yet, its not widely employed in the
> sorts of things that you might expect to find it due to its
> small size and level of integration.  E.g., I think most (?) cell
> phones use electret condensers (though I haven't taken many
> *different* makes/models apart to see how pervasive that claim).
> 
> What are the *downsides* of MEMS units?
> 
> What I'm looking for are guidelines that might be common to all
> such "transducers" with *specific* refinements that would
> apply to different technologies.  Most of the information I've
> found specifies those refinements in terms of cost or
> *signal* characteristics (use this for lots of dynamic range
> in signal; use that for a flat response; etc.)

There are so many different factors that affect reliability that it's
not possible to help without more information.

For example:
Many of the tiny mics (including most MEMS devices)  have very small
holes for the sound to get in - they are very susceptable to dirt. A
nice big traditional moving coil microphone with a 1.5" diameter is not
much upset by mouse crap sized particles but may  have other issues.

The MEMs mics are likely to be the most realible in terms of random
failures in benign conditions (because of the very automated and
controlled manufacturing process.)

So if you tell us what you want to do with it it may be possible to
help.

MK

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#459992

On 5/12/2017 8:02 AM, Michael Kellett wrote:
>> What I'm looking for are guidelines that might be common to all
>> such "transducers" with *specific* refinements that would
>> apply to different technologies.  Most of the information I've
>> found specifies those refinements in terms of cost or
>> *signal* characteristics (use this for lots of dynamic range
>> in signal; use that for a flat response; etc.)
>
> There are so many different factors that affect reliability that it's
> not possible to help without more information.
>
> For example:
> Many of the tiny mics (including most MEMS devices)  have very small
> holes for the sound to get in - they are very susceptable to dirt. A
> nice big traditional moving coil microphone with a 1.5" diameter is not
> much upset by mouse crap sized particles but may  have other issues.
>
> The MEMs mics are likely to be the most realible in terms of random
> failures in benign conditions (because of the very automated and
> controlled manufacturing process.)
>
> So if you tell us what you want to do with it it may be possible to
> help.

You're looking at it the wrong way.  I want to know what can
possibly be done WITH a microphone as a cheap transducer to
decide how I can apply them.

You'd like me to say "I want to deform a piece of metal; how
can I do that?"

Ans:
- wack it with a hammer
- bend it with some pliers
- swage it in a hydraulic press
- heat it to its melting point and drape it over a form
- selectively add/remove material to affect the net deformation

I, instead, am saying, "Hammers are cheap.  What sorts of things can
I do with them?  And, what are the things that will cause a hammer
to fail or be contraindicated in a particular application."
Ans:
    "You could use it to deform a piece of metal..."
    "You could use it as a paperweight..."
    "You could use it to drive a nail..."
    "You could use it as a tourniquet..."

[Ask yourself what uses you can devise for a microphone (or any
other transducer of your choosing).  If you can't come up with
a dozen (or score), you're not trying!]

As I mentioned previously, a friend uses them in qualifying new
engines -- "listen" for characteristic sounds of valve/lifter/rocker
noises instead of pulling the valve covers off after every N hours
of simulated wear.

Another firm has a device that uses a microphone to determine the
structural integrity of telephone poles.

Putting a microphone on a hot engine block exposes it to a different set
of stresses than holding it against a telephone pole.

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#459999

Don Y:
> On 5/12/2017 8:02 AM, Michael Kellett wrote:
>>> What I'm looking for are guidelines that might be common to all
>>> such "transducers" with *specific* refinements that would
>>> apply to different technologies.  Most of the information I've
>>> found specifies those refinements in terms of cost or
>>> *signal* characteristics (use this for lots of dynamic range
>>> in signal; use that for a flat response; etc.)
>>
>> There are so many different factors that affect reliability that
it's
>> not possible to help without more information.
>>
>> For example:
>> Many of the tiny mics (including most MEMS devices)  have very small
>> holes for the sound to get in - they are very susceptable to dirt. A
>> nice big traditional moving coil microphone with a 1.5" diameter is
not
>> much upset by mouse crap sized particles but may  have other issues.
>>
>> The MEMs mics are likely to be the most realible in terms of random
>> failures in benign conditions (because of the very automated and
>> controlled manufacturing process.)
>>
>> So if you tell us what you want to do with it it may be possible to
>> help.
> 
> You're looking at it the wrong way.  I want to know what can
> possibly be done WITH a microphone as a cheap transducer to
> decide how I can apply them.
> 
> You'd like me to say "I want to deform a piece of metal; how
> can I do that?"
> 
> Ans:
> - wack it with a hammer
> - bend it with some pliers
> - swage it in a hydraulic press
> - heat it to its melting point and drape it over a form
> - selectively add/remove material to affect the net deformation
> 
> I, instead, am saying, "Hammers are cheap.  What sorts of things can
> I do with them?  And, what are the things that will cause a hammer
> to fail or be contraindicated in a particular application."
> Ans:
>     "You could use it to deform a piece of metal..."
>     "You could use it as a paperweight..."
>     "You could use it to drive a nail..."
>     "You could use it as a tourniquet..."
> 
> [Ask yourself what uses you can devise for a microphone (or any
> other transducer of your choosing).  If you can't come up with
> a dozen (or score), you're not trying!]
> 
> As I mentioned previously, a friend uses them in qualifying new
> engines -- "listen" for characteristic sounds of valve/lifter/rocker
> noises instead of pulling the valve covers off after every N hours
> of simulated wear.
> 
> Another firm has a device that uses a microphone to determine the
> structural integrity of telephone poles.
> 
> Putting a microphone on a hot engine block exposes it to a different
set
> of stresses than holding it against a telephone pole.

OK - I finally get what you are after but I'm not that interested in
playing - 
I spent a fair chunk of my early engineering career designing and making
microphones and that branched out into accelerometers and from there we
moved into making knock sensors and supension control systems and then
to shock recorders and then the company went bust (15 years ago) and I
do other stuff now.

If I had a really good off the wall idea about using microphones I
wouldn't share it here :-)

But - more seriously - the question is just too open.

The only slightly novel thing I've considered recently is using some
cheapo ST MEMs mics with a frequency response up to 40kHz+ to make an
anemometer.

MK

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#460003

On 5/12/2017 10:08 AM, Michael Kellett wrote:
> OK - I finally get what you are after but I'm not that interested in
> playing -
> I spent a fair chunk of my early engineering career designing and making
> microphones and that branched out into accelerometers and from there we
> moved into making knock sensors and supension control systems and then
> to shock recorders and then the company went bust (15 years ago) and I
> do other stuff now.
>
> If I had a really good off the wall idea about using microphones I
> wouldn't share it here :-)

You'll note I've not shared any of mine!  :>

> But - more seriously - the question is just too open.
>
> The only slightly novel thing I've considered recently is using some
> cheapo ST MEMs mics with a frequency response up to 40kHz+ to make an
> anemometer.

I'm not looking for ideas as to how to use them.  I'm looking for
general information of their vulnerabilities, contraindicators, etc.

E.g., I might come up with a great application but not be able
to find an (affordable!) device that could operate in the constraints
that the application dictates without damaging the "transducer".

So, I'm more looking for things like:
- microphones don't like getting wet
- microphones don't like being subjected to prolonged periods of high heat
- microphones subjected to frequent mechanical shock fail prematurely
- microphones don't like rapid temperature cycling
etc.

The "typical" way of thinking of microphones is in conjunction with
a human-oriented activity.  So, they are specified for "human occupied
environments" and applications that are more related to human hearing
than as general purpose transducers.

E.g., I've a buddy with a recording studio who can tell me why each
particular microphone is best suited (dollars vs. effectiveness)
for each "sound source".  But, completely helpless to tell me how
those evaluations would change if I tweaked the environment:
     "What if I wanted to record a saxophone playing in a freezer?"

I don't want to pick a mic technology only to find that the common
knowledge about it is useless outside of that *typical* application
frame.  Or, even approach a problem with an "audio" sensor if there
are NO technologies that are suitable!

For example, when tablets are manufactured (by compressing "powdered
granulation"), a common problem is air becoming entrapped in the
"powder" as it is compressed.  When the pressure is released, the
compressed air causes the tablet to "explode" (the top pops off).

This could be sensed audibly by locating a microphone adjacent to
the tablets' path of motion and listening to the sound that accompanies
the release of the compressive force (heavy filtering but you *know*
what the fundamental frequency of the signal is, a priori).

But, it would be an impractical environment as the inevitable accumulation
of the powdered "granulation" would quickly render the microphone
("acoustical transducer") useless.

You'd never encounter this problem in a more traditional microphone
application!  :>

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#460040

Why Don wrote:

--------------


** Is this steaming great moron for real ?? 


FFS:

If you place a mic inside a plastic bag it becomes proof against moisture, water and dust. Sound transfers as usual.

If the environment is vibrating severely, mount the mic on a rubber isolator. 

If it is absurdly cold, heat the mic with a resistor. 

Wot a tedious, bloody TROLL !!!!



....  Phil 

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#460102

On Fri, 12 May 2017 11:02:27 -0700, Don Y wrote:
 
> For example, when tablets are manufactured (by compressing "powdered
> granulation"), a common problem is air becoming entrapped in the
> "powder" as it is compressed.  When the pressure is released, the
> compressed air causes the tablet to "explode" (the top pops off).
> 
> This could be sensed audibly by locating a microphone adjacent to the
> tablets' path of motion and listening to the sound that accompanies the
> release of the compressive force (heavy filtering but you *know*
> what the fundamental frequency of the signal is, a priori).
> 
> But, it would be an impractical environment as the inevitable
> accumulation of the powdered "granulation" would quickly render the
> microphone ("acoustical transducer") useless.
> 
> You'd never encounter this problem in a more traditional microphone
> application!  :>

Separate the sensor and electronics. Sensor can be a robust piece of
metal foil etc. Or even the material itself. Bounce a laser beam off
of it to a photocell and "listen" for characteristic "sounds".
Such a solution would be very inexpensive compared to traditional
microphone technology and far less subject to the environment.

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#460109

On 5/13/2017 10:19 AM, Terry Newton wrote:
> On Fri, 12 May 2017 11:02:27 -0700, Don Y wrote:
>
>> For example, when tablets are manufactured (by compressing "powdered
>> granulation"), a common problem is air becoming entrapped in the
>> "powder" as it is compressed.  When the pressure is released, the
>> compressed air causes the tablet to "explode" (the top pops off).
>>
>> This could be sensed audibly by locating a microphone adjacent to the
>> tablets' path of motion and listening to the sound that accompanies the
>> release of the compressive force (heavy filtering but you *know*
>> what the fundamental frequency of the signal is, a priori).
>>
>> But, it would be an impractical environment as the inevitable
>> accumulation of the powdered "granulation" would quickly render the
>> microphone ("acoustical transducer") useless.
>>
>> You'd never encounter this problem in a more traditional microphone
>> application!  :>
>
> Separate the sensor and electronics. Sensor can be a robust piece of
> metal foil etc.

In the above example, a microphone is impractical -- due to other
constraints imposed by the application.  E.g., the tabletting area
has to be "cleanable" to ensure product from "tabletted compound X"
doesn't contaminate "tabletted compound Y" (you wouldn't want
the BABY ASPIRIN that you make in the afternoon to have traces of
the VIAGRA that you made in the morning!  :> )

So, any sensor in the tabletting area has to be cleanable.  Does this
require removing the sensor to clean it "off line"?  Is the later
(re)placement of the sensor critical (you wouldn't want to have to
recalibrate things just because you removed a sensor!)?

Do you have to pot/encapsulate a portion of the sensor to make it
cleanable?  Does this further attenuate the signal you're trying to
sense?

I posed this example to my recording studio friend as he'd seen
one of these pieces of equipment "in action" in the lab on one of
his visits.  The tablet is formed between a pair of stainless steel
"punches" while surrounded by a stainless steel "die" (imagine
putting some powder in a tube and then compressing it *in* the
tube by plunging pegs in each end of the tube; i.e., the tablet is
surrounded by steel as it is being compressed -- several tons of
pressure exerted in a millisecond or three).

You're surrounded by the noise of the mechanism (you're making 35-75
tablets concurrently) and trying to hear a little "pop" that is
muffled inside a steel box -- that is MOVING past your sensor.

The analogy we came up with was mic'ing a kettle drum and recording
its performances -- and, later, trying to decide *if* and *when*
a grain of rice might have been on the membrane (detected by hearing
the rice "bouncing" as the membrane is struck).

Had he a fair bit of experience in that application domain, he would
have realized the dynamic range and sensitivity involved and would
have "waved off" a microphonic solution.

Easier to have a component vendor characterize their components
(e.g., sensors... microphones) than to educate the component vendor
of the varied constraints imposed by the application and HOPE
they can recommend something suitable!  :>

Imagine having potentially dozens of different applications and
having to bring a supplier (or <someone>) up to speed on ALL of
their constraints before they can offer a recommendation vs. letting
THEM educate you on the capabilities/characteristics/liabilities
associated with their "supplies"

(Most folks have experience in very few application domains)

> Or even the material itself. Bounce a laser beam off
> of it to a photocell and "listen" for characteristic "sounds".
> Such a solution would be very inexpensive compared to traditional
> microphone technology and far less subject to the environment.

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#460113

On a sunny day (Sat, 13 May 2017 11:57:17 -0700) it happened Don Y
<blockedofcourse@foo.invalid> wrote in <of7kne$tbc$1@dont-email.me>:

>You're surrounded by the noise of the mechanism (you're making 35-75
>tablets concurrently) and trying to hear a little "pop" that is
>muffled inside a steel box -- that is MOVING past your sensor.

Digital signal processing.
The problem is not the mike.

You need the spectrum of the 'pop', do an FFT, and look for it.

There are other ways, train a neural net etc etc.

No mike is perfect.
And this seems in the LF range, no wideband needed.

It is just a specific pressure wave,

But I do not want to start an in depth discussion about mikes,
I had my part of that, worked in TV and film studio.
Almost as many opinions as people.
And I have no experience with MEMS mikes.

You could try learning to write some code.
In C that is :-)

Endlessly babbling about it gets you nowhere.

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#460212

On a sunny day (Sat, 13 May 2017 19:12:08 GMT) it happened Jan Panteltje
<pNa0nStpealmtje@yahoo.com> wrote in <of7lq8$136v$1@gioia.aioe.org>:

>On a sunny day (Sat, 13 May 2017 11:57:17 -0700) it happened Don Y
><blockedofcourse@foo.invalid> wrote in <of7kne$tbc$1@dont-email.me>:
>
>>You're surrounded by the noise of the mechanism (you're making 35-75
>>tablets concurrently) and trying to hear a little "pop" that is
>>muffled inside a steel box -- that is MOVING past your sensor.
>
>Digital signal processing.
>The problem is not the mike.
>
>You need the spectrum of the 'pop', do an FFT, and look for it.
>
>There are other ways, train a neural net etc etc.
>
>No mike is perfect.
>And this seems in the LF range, no wideband needed.
>
>It is just a specific pressure wave,
>
>But I do not want to start an in depth discussion about mikes,
>I had my part of that, worked in TV and film studio.
>Almost as many opinions as people.
>And I have no experience with MEMS mikes.
>
>You could try learning to write some code.
>In C that is :-)
>
>Endlessly babbling about it gets you nowhere.

So this is how you _could_ go about it:
Mount a microphone near that process, use one that is not obviously crap.
Take your decent quality PC / laptop and record.
Start you stopwatch watch and make a note of the times things go wrong (pop).
Maybe MAKE things go wrong to get the pop sound.

Thank everyone, leave the mike in place, bolted or welded,
create a job for somebody guarding it, contact the White House you created an other American job,
also hire somebody to train these people who will in turn watch the microphone and prevent it from being
moved or obstacles placed in front of it or it being used for other purposes.
thank everybody again, and your president of course,
go home, run your recording, do some FFT, look if you see a difference between 'plop' and normal 'pluff'
sounds, if not contact everybody involved that more money and resources are needed.
If there is a visible difference subtract the  spectra, and use that as trigger for whatever,
counter, activator, email, alarm, sprinkler, fire brigade, anti-terrorist squad,
flashing lights, you name it.
Homework, could be fun.
Once you have the soft (IF you have the soft) then sell them your PC, train a user to configure it
boot it, mail the White House again you created  yet an other American job,
and do not forget to _charge_ for it.

 
Solar cells sucking , what do you know.

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#460215

On a sunny day (Sat, 13 May 2017 19:12:08 GMT) it happened Jan Panteltje
<pNa0nStpealmtje@yahoo.com> wrote in <of7lq8$136v$1@gioia.aioe.org>:

PS
I forgot the vow of silence,
all operators should take one, and no farting either.

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#460218

On a sunny day (Sun, 14 May 2017 09:17:05 GMT) it happened Jan Panteltje
<pNa0nStpealmtje@yahoo.com> wrote in <of97ah$11l8$1@gioia.aioe.org>:

>On a sunny day (Sat, 13 May 2017 19:12:08 GMT) it happened Jan Panteltje
><pNa0nStpealmtje@yahoo.com> wrote in <of7lq8$136v$1@gioia.aioe.org>:
>
>PS
>I forgot the vow of silence,
>all operators should take one, and no farting either.

And, com to sink of it,
I think it is best to use one of those parabola mikes,
to get a narrow target beam,
and mount it in a rubber mount against vibration,
maybe hanging from the ceiling.

 

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#460114

On Sat, 13 May 2017 11:57:17 -0700, Don Y wrote:

>>> For example, when tablets are manufactured (by compressing "powdered
>>> granulation"), a common problem is air becoming entrapped in the
>>> "powder" as it is compressed.  When the pressure is released, the
>>> compressed air causes the tablet to "explode" (the top pops off).

>> Separate the sensor and electronics. Sensor can be a robust piece of
>> metal foil etc.
> 
> In the above example, a microphone is impractical -- due to other
> constraints imposed by the application.  E.g., the tabletting area has
> to be "cleanable" to ensure product from "tabletted compound X" doesn't
> contaminate "tabletted compound Y" (you wouldn't want the BABY ASPIRIN
> that you make in the afternoon to have traces of the VIAGRA that you
> made in the morning!  :> )
.....
> You're surrounded by the noise of the mechanism (you're making 35-75
> tablets concurrently) and trying to hear a little "pop" that is muffled
> inside a steel box -- that is MOVING past your sensor.

Isn't this a visual inspection issue? using a mic to hear a pop
seems redundant when you can just look at it to see if it popped.
But a laser-based sound sensor (if that's what you want) will be
far more robust than anything with electronics where it needs
to be cleaned. Just hose it off, no electronics to get wet.

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#460119 — Re: Microphone risk factors (OT -- long)

On 5/13/2017 12:26 PM, Terry Newton wrote:
> On Sat, 13 May 2017 11:57:17 -0700, Don Y wrote:
>
>>>> For example, when tablets are manufactured (by compressing "powdered
>>>> granulation"), a common problem is air becoming entrapped in the
>>>> "powder" as it is compressed.  When the pressure is released, the
>>>> compressed air causes the tablet to "explode" (the top pops off).
>
>>> Separate the sensor and electronics. Sensor can be a robust piece of
>>> metal foil etc.
>>
>> In the above example, a microphone is impractical -- due to other
>> constraints imposed by the application.  E.g., the tabletting area has
>> to be "cleanable" to ensure product from "tabletted compound X" doesn't
>> contaminate "tabletted compound Y" (you wouldn't want the BABY ASPIRIN
>> that you make in the afternoon to have traces of the VIAGRA that you
>> made in the morning!  :> )
> .....
>> You're surrounded by the noise of the mechanism (you're making 35-75
>> tablets concurrently) and trying to hear a little "pop" that is muffled
>> inside a steel box -- that is MOVING past your sensor.
>
> Isn't this a visual inspection issue? using a mic to hear a pop
> seems redundant when you can just look at it to see if it popped.

You're producing ~200 tablets a SECOND.  They are typically collected in
a *barrel* due to the quantity involved.  *One* of the discharge chutes
is visible in the left of this photo:
    <http://www.chrishillsethenterprises.com/images/P/400%20Manesty.jpg>
It's mate is hidden on the opposite side of the machine.  The large
black knobs control physical dimensions of the tablets plus where
(vertically) in the die it is formed.

There are camera inspection systems but they are expensive and have to
be tuned to the tablet geometry in question -- different tablets have different
shapes, some have holes in the center, etc.  And, the tablets are essentially
airborn when they exit the process -- you can't tell which side will be "up"
or "facing the camera(s)" (the bottom can pop off just like the top).

Lower right corner shows oblong tablets falling off a "deduster" into
a collection barrel; another deduster can be seen behind it on the far
side of the machine:
    <http://www.dmcindustries.com/ProductImages/112319/md_8ba5a4_1614b.jpg>

Additionally, you want to know about it in relatively real-time.  If you
have a production problem, you don't want to *keep* producing "defects".

A microphone is just a bad choice of sensor despite the apparent applicability
(imagine taking one 1/4inch "cell" from a piece of bubble wrap and driving a
diesel truck over it and trying to hear it pop -- given that it might not
even be present!)

Photo of a top view (the bottom view is the mirror image -- including the
large cylindrical LOWER punches that mirror the UPPER punches, shown here)
of a turret from a smaller machine to give you an idea of how the tablets
are formed (badly maintained, rusty, etc.):
   <https://www.fraingroup.com/wp-content/uploads/5D4776Y.jpg>

Note the oblong-shaped die exposed in the lower center.  If you could look
straight down into it, you would see the LOWER punch has been raised up
into it from below.  This gives you a cavity with an open top (before
the UPPER punch is driven into it).

The brass structure to the right (turret rotates clockwise so that represents
an earlier "place" in time for the die) is the feed frame.  Its full of
granulation ("pill powder") and falls into the open-topped die as they
pass beneath it.  The feed frame sits *on* the top surface of the turret/die
so it scrapes any excess off of each cavity as the cavity passes outside the
scope of the feed frame.  I.e., the height of the LOWER punch as it passes
under the feed frame determines the volume of the cavity -- the amount of
granulation that (theoretically) will be drawn into the cavity.

Once clear of the feedframe, the LOWER punch is pulled down to move the
granulation to a more opportune portion of the die (i.e., away from the top
edge).  Then, the UPPER punch is driven down into the cavity from above
while the LOWER punch holds its own vertical position.

Compression force is applied by the punches (upper and lower) being forced
between a pair of stationary rollers, one of which is visible in the extreme
upper left corner of the photo.  It's mate is not visible but acting on the
LOWER punch from below.

The distance between the upper and lower ROLLERS thus determines the
compressed thickness of the finished tablet; the volume of the cavity
as it passed through the feed frame determines the *weight* of the tablet;
the fixed dimensions of the die determine the outline of the tablet.
The material+dimensions+compressive force determine the hardness of the
tablet.  All of these are criteria that can be used to reject a
tablet as "defective".

Of course, punches and dies have tolerances on their physical dimensions
so you get a *range* of "nominal tablets" from the press;  trying to control
the process involves controlling a bunch of REALLY SIMILAR, but different,
processes running simulataneously yet sharing certain common aspects (e.g.,
the feedframe, rollers, etc.)

As the turret rotates, it may see 2 or 4 such "compressing events" on
each "station" (UPPER+LOWER+DIE) before the tablet is ejected by lifting
the UPPER punch off of the tablet WHILE raising the LOWER punch to force
the compressed tablet from the die.  Some machines have a two-stage compression
cycle -- a lighter force to "tamp" the granulation down followed by a
heavier compression force to *form* the tablet.

Some machines can make (or be reconfigured to make -- at a large fraction
of a megadollar you want to be able to apply the machine to a wide variety
of products!) "two layer" tablets by making the first layer on one
"side" of the machine and NOT ejecting it; rather, adding more (different)
granulation on top of it and forming the composite tablet on the second
"side" of the machine before ejecting a finished tablet.

[E.g., I think there was a popular antacid that was very obviously a
two-layered product -- with different colored layers to stress this.
More recently, two-layer tablets find use in osmotic pump delivery
systems for controlled rate of drug delivery:  the tablet is coated
with an insoluble film that acts as a semi-permeable membrane; the
membrane has a hole laser-drilled through it on the "active" (drug)
layer side of the tablet; the "far" layer/side of the tablet is
a hydrophilic substance that swells as moisture is absorbed through
the membrane thus *pushing* the active ingredient out through the
drilled orifice.  By tweeking the permeability of the coating layer
and swelling characteristics of the "pusher" layer, you can predict
the rate at which the active will be "dispensed"]

The "pop" occurs as the compressive pressure is released from the
tablet -- so, it occurs while the tablet is "buried" within the
upper+die+lower envelope.  *As* the tablet is batted off the turret,
you want to decide "Go-NoGo" and deflect defective tablets into a
scrap bin -- before the next tablet appears in 10ms and has to be
similarly dispatched.  Screw up and let a defective tablet fall
into the "good" bin and you have to inspect its entire contents
to find the offender(s).  This also can invalidate your process:
"How did a bad tablet NOT get detected and deflected?  What's
wrong with your *process* given that it was designed not to allow
this to happen?"

The "popped off" piece may be ejected with the tablet, or it may cling
to the face of the upper/lower punch and fall off at some later point.
Or, it may hang around and screw up the next tabletting formulation on
that station as it goes 'round again.

> But a laser-based sound sensor (if that's what you want) will be
> far more robust than anything with electronics where it needs
> to be cleaned. Just hose it off, no electronics to get wet.

I.e., use a technology that is easier to clean and more sensitive
in light of the dynamic range of the "signal"!  :>

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#460105

On Friday, May 12, 2017 at 1:13:28 PM UTC-4, Michael Kellett wrote:


> 
> If I had a really good off the wall idea about using microphones I
> wouldn't share it here :-)
> 

> MK

I am not very concerned with telling off the wall applicaions.

One is  to come up with an array of microphones , hooked to amps and speakers to make an active sound absorber.  There are many restaurants that have such ambient noise that one can not talk to one's dinner companion.  Not sure one could actually sell such things.  I  think the restaurant owners think that lots of noise is a good thing.  Could possibly be used for reduction of noise in air planes or heavy trucks.

Another is using a mike  at each end of a pole to make a directional sound sensor.  Small market for locating earthquake victims and lost hikers.  Possible replacement for shotgun mikes used for TV and movies.

Another is heterodyning ultrasonic sounds to audio frequencies for locating gas , air and steam leaks.  Again not a large market.  Could also be used for amusement in listening to bats.

And one last one is sensing intruders.  Possible market is the wall between Mexico and the U.S.  Think detection of tunnels being dug and primacord being used to make holes 

                           Dan

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#460112

On 5/13/2017 11:06 AM, dcaster@krl.org wrote:
> On Friday, May 12, 2017 at 1:13:28 PM UTC-4, Michael Kellett wrote:
>
>> If I had a really good off the wall idea about using microphones I
>> wouldn't share it here :-)
>
> I am not very concerned with telling off the wall applicaions.

"Off the wall" is easy -- witness my tabletting example (much better
solved with other technologies).

But, how "concerned" would you be about disclosing something you (or
your firm) were pursuing, at the moment?

> One is  to come up with an array of microphones , hooked to amps and
> speakers to make an active sound absorber.  There are many restaurants that
> have such ambient noise that one can not talk to one's dinner companion.
> Not sure one could actually sell such things.  I  think the restaurant
> owners think that lots of noise is a good thing.  Could possibly be used for
> reduction of noise in air planes or heavy trucks.

I'm not sure you could do that without making it a *distributed* system
as the "noise" received at each diner's location would originate from
many different sources (e.g., other diners!).

I think they have made systems like this for noise cancelling exhaust
systems, though.

It would also be helpful in the rear of aircraft to help mute the
sound of the engine(s) located by the rear of the aircraft.

> Another is using a mike  at each end of a pole to make a directional sound
> sensor.  Small market for locating earthquake victims and lost hikers.
> Possible replacement for shotgun mikes used for TV and movies.
>
> Another is heterodyning ultrasonic sounds to audio frequencies for locating
> gas , air and steam leaks.  Again not a large market.  Could also be used
> for amusement in listening to bats.

Sensing how full a grain silo is WHILE it is being filled...

> And one last one is sensing intruders.  Possible market is the wall between
> Mexico and the U.S.  Think detection of tunnels being dug and primacord
> being used to make holes

I think the "virtual fence" already does that.  There are geophones (?)
distributed in the desert through which border monitors can detect the
footsteps of "illegals" in the area.  This is possible because there's
nothing ELSE out there!  :>

Tunnels tend to be dug in metropolitan areas -- i.e., so the terminus can be
hidden (e.g., inside a home).  There, you have lots of other "normal"
sounds that can hide the signal.

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