Meaning of this Microphone spec...

On 11/29/2020 7:54 PM, Lasse Langwadt Christensen wrote:
mandag den 30. november 2020 kl. 01.32.09 UTC+1 skrev Cursitor Doom:
On Sun, 29 Nov 2020 11:35:51 -0600, amdx <am...@knology.net> wrote:
On 11/29/2020 11:22 AM, John Larkin wrote:
On Sun, 29 Nov 2020 10:46:53 -0600, amdx <am...@knology.net> wrote:

Looking at a electret condensor mic, it has a spec, \"Decreasing Voltage
(3VS to 2VS ) -3dB\"

What does that mean?
Gain drops as supply voltage drops. It would be even worse at 1 volt.

https://www.mouser.com/datasheet/2/334/AOM-5024L-HD-R-1219369.pdf
Also, the frequency response graph is labeled (db/1V) and shows it down
37 at 18kHz, that can\'t be down 37db at 18Khz.

What does that mean?
It\'s \"down\" about 12 dB at that notch, -25 to -37 dBv. Probably some
resonance.

Thanks all, doesn\'t seem like a great mic.
Depends what you want to use it for! Not much use for high quality
music recording at any rate.

look up the frequency response of an SM57 and SM58
a helluva lot of music has been recorded and performed with those two
Click to expand...

The SM58 is a very good dynamic mic for vocals and spoken-word
recordings, especially if the recording environment is untreated.

The frequency response doesn\'t look \"uncolored\" but it seems fairly flat
in practice. It\'s a meatloaf mic, not amazing, not bad
 
On Sunday, November 29, 2020 at 11:47:04 AM UTC-5, amdx wrote:
Looking at a electret condensor mic, it has a spec, \"Decreasing Voltage
(3VS to 2VS ) -3dB\"

What does that mean?

https://www.mouser.com/datasheet/2/334/AOM-5024L-HD-R-1219369.pdf

Also, the frequency response graph is labeled (db/1V) and shows it down
37 at 18kHz, that can\'t be down 37db at 18Khz.

What does that mean?

Mikek


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Click to expand...

Only of tangential interest, but there is a nice series of microphone videos
on the EEVblog. Interesting stuff.

George H.
 
George Herold wrote:
==================
Only of tangential interest, but there is a nice series of microphone videos
on the EEVblog.
Click to expand...

** Tangential for sure - cos it tells you SFA about microphones

The \"expert\" at the white board is Doug Ford, a former mate of mine. He began working for
Australia\'s leading microphone maker ( Rode) without having a single clue..
They did not have a clue either - just copied things made in China.

Doug relied on me for a lot of advice, pointing him away from dead ends and into usable directions.

> Interesting stuff.

** Not really.

....... Phil
 
On Monday, November 30, 2020 at 5:08:44 PM UTC-5, palli...@gmail.com wrote:
George Herold wrote:
==================

Only of tangential interest, but there is a nice series of microphone videos
on the EEVblog.
** Tangential for sure - cos it tells you SFA about microphones

The \"expert\" at the white board is Doug Ford, a former mate of mine. He began working for
Australia\'s leading microphone maker ( Rode) without having a single clue..
They did not have a clue either - just copied things made in China.

Doug relied on me for a lot of advice, pointing him away from dead ends and into usable directions.

Interesting stuff.

** Not really.

...... Phil
Click to expand...
Grin, OK. I know SFA about mics...I\'m easily confused.
I liked the part about the mic having two ports.
One only weakly linked to the air. It does the ~ DC.
Splitting the frequency response into two parts is a good trick.

George H.
 
On 12/1/2020 10:10 AM, jlarkin@highlandsniptechnology.com wrote:
On Mon, 30 Nov 2020 23:39:05 -0800 (PST), Phil Allison
pallison49@gmail.com> wrote:

bitrex the bit brain wrote:
--------------------------------------

The \"expert\" at the white board is Doug Ford, a former mate of mine. He began working for
Australia\'s leading microphone maker ( Rode) without having a single clue..
They did not have a clue either - just copied things made in China.
Well that\'s different...
** Not so much when you know the whole story.

\"Rode\" is a name invented here to make cheap Chinese SPL meters seem European and better sellers.
Involved a simple screen printing job plus translating the operator\'s manual. The Chinese meter used a
copied European condenser capsule ( CSM-25) and was a clone of a 1960s B&K model.
All Chinese made parts inside, Si & Ge BJTs, JFETs, op-amps the lot.

I still have a couple of them myself.

They same maker produced a large diaphragm mic that was styled like something out of the 1950s. So the
Rode people ( Freedman Electronics in Sydney) bought capsules, loaded PCBs and transformers from the
Chinese and built the bits into a modem looking case made here. That became the Rode NT-1 (aka the Rodent) .

This pile of bits sold like hot cakes round the world, so a new company was formed ( Rode Microphones ) and
with new premises began large scale production. As new capsule designs became available from China, new
model mics appeared labelled \" Rode\". Including hand held models, a tube model etc , which Mr Ford had a
large hand in. Hand stuffed PCBs were replaced with professional SMD versions and nice metal work for them
was sourced. The output tranny disappeared and was replaced by one of Doug\'s active balanced designs.

A great deal was also \"discovered\" by studying the schematics for every famous European mic Rode could get
their fingers on.

Just when this was all going nicely, a falling out with management saw Doug Ford leave for greener pastures.

There is only so much a \" Koala can Bear. \"


..... Phil
One could put a lot of tiny MEMS or electret mikes on one PC board. I
wonder what could be done with that. And maybe a bit of DSP? A
phased-array microphone?
Click to expand...
 Here\'s a parametric speaker, ya, works different than a phased array,
but it\'s neat.

https://www.youtube.com/watch?v=x17iNaJfNLI
   Mikek
Click to expand...


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upsid...@downunder.com wrote:
===============================
It would interesting to have a WW I aerial combat movie or game, such
as Sopwith Camel against Fokkers with sound sources from all
directions :).
Click to expand...

** Sure would.

You just reminded me of a BBC radio interview with a WW2 Spitfire pilot.

IIRC it was broadcast some time in the late 1970s.

The pilot was describing an interaction with some German airman with the words:

\" .... then these three *fokers* come down at me, out of the sun..... \"

The BBC interviewer quickly interrupted him - and with his \"plumb in mouth\" accent explained that the squadron leader was referring to the \" Faulk Wolfe 190 \" fighter aircraft - also sometimes know as \" fokers\" .

\" Nooooooh.... \" exclaimed the now very annoyed WW2 pilot -

\" ..... these three *fuckers* were flying \" Messerschmitts \" !!\"



....... Phil
 
On 01.12.20 5:10 pm, jlarkin@highlandsniptechnology.com wrote:
One could put a lot of tiny MEMS or electret mikes on one PC board. I
wonder what could be done with that. And maybe a bit of DSP? A
phased-array microphone?
Click to expand...

There is a Swiss company building something like that, Distran. They use
some 100 microphones on a PCB to generate data with angular resolution,
and display it as an overlay over images from an integrated camera
module. Target market appears to be gas leak-finding e.g. in
petrochemical plants, or detection of corona discharge.

— David
 
On Thursday, 3 December 2020 at 10:12:50 UTC, David Nadlinger wrote:
On 01.12.20 5:10 pm, jla...@highlandsniptechnology.com wrote:
One could put a lot of tiny MEMS or electret mikes on one PC board. I
wonder what could be done with that. And maybe a bit of DSP? A
phased-array microphone?
There is a Swiss company building something like that, Distran. They use
some 100 microphones on a PCB to generate data with angular resolution,
and display it as an overlay over images from an integrated camera
module. Target market appears to be gas leak-finding e.g. in
petrochemical plants, or detection of corona discharge.

— David
Click to expand...

Its not a new idea. The following paper, submitted in 1975, describes an
acoustic telescope using an array of microphones with digital signal
processing to image the noise generation by jet engines.

\"The acoustic telescope. J.Billingsley & R.Kinns
Department of Engineering, University of Cambridge, Cambridge CB21PZ, England
Received 28 October 1975, Revised 3 June 1976, Available online 25 July 2003.\"

https://www.sciencedirect.com/science/article/abs/pii/0022460X76905526

John
 
On 12/2/2020 12:07 PM, upsidedown@downunder.com wrote:
On Wed, 02 Dec 2020 07:39:08 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Wed, 02 Dec 2020 08:51:42 +0200, upsidedown@downunder.com wrote:

On Tue, 01 Dec 2020 08:10:46 -0800, jlarkin@highlandsniptechnology.com
wrote:


One could put a lot of tiny MEMS or electret mikes on one PC board. I
wonder what could be done with that. And maybe a bit of DSP? A
phased-array microphone?

Thanks to the small dimensions of these microphone capsules. all four
microphones in Ambisonic https://en.wikipedia.org/wiki/Ambisonics
tetrahedron can be put into a single point even at 20 kHz (wavelength
16 mm).

The signals can be used to produce the B-format (W, x, y, z) channels,
which can then be used to produce different radiation patterns, such
as cardioid and aim it into different directions, either in real time
or in post processing.

Right. The array can be aimed. S/N improves with more mikes, too.

The mikes could be arranged in a horizontal pattern too, for 360
degree aiming in the horizontal plane. The tiny mikes could be treated
as point pressure sensors. Or even 3D arrays.

The sound field microphone
https://en.wikipedia.org/wiki/Soundfield_microphone is of course 3D,
containing also the height information.

One problem with 3D sound reproduction is the layout of speakers. Some
use two speakers down front, two speakers up front and two speakers in
the back.

Imagine a 3D video display, showing sound waves traveling through the
array, and projected sources.

It would interesting to have a WW I aerial combat movie or game, such
as Sopwith Camel against Fokkers with sound sources from all
directions :).
Click to expand...

Here you are:

<https://youtu.be/GMTpuRgqrNk?t=88>
 
On 12/3/2020 11:18 AM, bitrex wrote:
On 12/2/2020 12:07 PM, upsidedown@downunder.com wrote:
On Wed, 02 Dec 2020 07:39:08 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Wed, 02 Dec 2020 08:51:42 +0200, upsidedown@downunder.com wrote:

On Tue, 01 Dec 2020 08:10:46 -0800, jlarkin@highlandsniptechnology.com
wrote:


One could put a lot of tiny MEMS or electret mikes on one PC board. I
wonder what could be done with that. And maybe a bit of DSP? A
phased-array microphone?

Thanks to the small dimensions of these microphone capsules. all four
microphones in Ambisonic https://en.wikipedia.org/wiki/Ambisonics
tetrahedron can be put into a single point even at 20 kHz (wavelength
16 mm).

The signals can be used to produce the B-format (W, x, y, z) channels,
which can then be used to produce different radiation patterns, such
as cardioid and aim it into different directions, either in real time
or in post processing.

Right. The array can be aimed. S/N improves with more mikes, too.

The mikes could be arranged in a horizontal pattern too, for 360
degree aiming in the horizontal plane. The tiny mikes could be treated
as point pressure sensors. Or even 3D arrays.

The sound field microphone
https://en.wikipedia.org/wiki/Soundfield_microphone is of course 3D,
containing also the height information.

One problem with 3D sound reproduction is the layout of speakers. Some
use two speakers down front, two speakers up front and two speakers in
the back.

Imagine a 3D video display, showing sound waves traveling through the
array, and projected sources.

It would interesting to have a WW I aerial combat movie or game, such
as Sopwith Camel against Fokkers with sound sources from all
directions :).


Here you are:

https://youtu.be/GMTpuRgqrNk?t=88
Click to expand...

Obviously the audio for the user is stereo headphones but it uses
head-tracking to position the sound sources in the stereo field
dynamically as the user looks around
 
On 12/3/2020 4:52 AM, Phil Allison wrote:
upsid...@downunder.com wrote:
===============================

It would interesting to have a WW I aerial combat movie or game, such
as Sopwith Camel against Fokkers with sound sources from all
directions :).


** Sure would.

You just reminded me of a BBC radio interview with a WW2 Spitfire pilot.

IIRC it was broadcast some time in the late 1970s.

The pilot was describing an interaction with some German airman with the words:

\" .... then these three *fokers* come down at me, out of the sun..... \"

The BBC interviewer quickly interrupted him - and with his \"plumb in mouth\" accent explained that the squadron leader was referring to the \" Faulk Wolfe 190 \" fighter aircraft - also sometimes know as \" fokers\" .

\" Nooooooh.... \" exclaimed the now very annoyed WW2 pilot -

\" ..... these three *fuckers* were flying \" Messerschmitts \" !!\"



...... Phil
Click to expand...

Here\'s a VR Fokker, fokker:

<https://www.youtube.com/watch?v=ISDsSn1nh9c>
 
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