Re: Learning more - Ultrasonic Microphone building
I'm also interested in the topic but I would like to record well over 100k. :-)
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I recently had the opportunity to record sounds from . According to the inventor, some of the instruments produce sounds in the ultrasonic range up to 500 kHz and that the ultrasonic sounds have a positive effect on the audible frequency range. I asked how this was measured and was told that an was used to study the sound characteristics of the stone instruments. It was confirmed that the sound of some instruments was reliably measured up to about 200 kHz and beyond.
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I don't want to hijack this thread, but I would like to ask two questions.
I would like to give it a try to record the stone instrument with ultrasonic mics.
Is it feasible as a hobbyist to build a low-noise, high-sensitivity microphone to record in the audible and ultrasonic range well above 100k? Are there any instructions for building a SimpleP48Ultra maybe?!?!
Has anyone tried the Dodotronic USB Ultramics which seem to record up to 384k?
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I found the following articles by Zach Poff interesting:
and
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- Heinz
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On Sat, Dec 28, 2024 at 03:59 AM, <soundwichartist@...> wrote:
Learning more about building ultrasonic microphones, I posted a while ago about ultrasonic electret mics. I've found the advantages of them for sure, being nice and easy. learning more and more though, I'm looking for something that gets up to 100k, like the oh-so expensive Sanken CO-100k. I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more. does anyone offer capsules that have that sort of response? If not, what are the other options for achieving this high of a response? Is the only option to build them myself? As a sound designer, I'm looking to capture the largest amount of frequencies possible.?
Thank you again, you incredibly knowledgeable people!?
-Soundwich
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Re: Learning more - Ultrasonic Microphone building
On Sun, Jan 5, 2025 at 06:51 AM, Zander wrote
.... In terms of electret capsules, the best I've found so far is the Primo em258, but this has a pretty steep upper frequency rolloff, so your SNR at 100kHz is more than 40dB worse than it is at 20kHz, but even a Simple P48 build with this is going to give you access to frequencies that no regular studio mics will.
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I too discovered that the EM258 has a steep roll off above about 50KHz.? ?The Knowles MEMs SPU1410 capsule is a lot better than that, and at least there is a published HF frequency response for that particular capsule, which I linked to earlier- see here:
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As you can see, it's horribly non linear, but at least the noise profile follows the frequency response, so correcting? for that maintins the S/N ratio at higher frequencies.
It's also not an easy response to correct for with simple analogue filters, so I tend to do it in post , by running my bat recordings through an appropriate EQ script.
( Some details on the last page of my ultrasonic mic notes you can find on this page: ? )
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The best ultrasonic repsonse I've seen from a studio mic is the Sennheiser MKH8020....? Bit too expensive for simple bat echo-location recordings though !
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Re: Learning more - Ultrasonic Microphone building
As for the ultrasonic sound source (limited frequency range, obviously) could serve a "dog whistle". Or several, from different manufacturers. As I imagine that they would differ in produced frequencies.
Such a whistle (or several) connected to a cheap pressure regulator and a source of compressed air (even a car tyre will suffice or a sprayer mentioned above) is should give relatively consistent results. And be quite easy to put together.
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Easier than befriending a bat.
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Re: Learning more - Ultrasonic Microphone building
Re: measurements, I'd be very wary of the frequency response of anything you can produce with audio equipment that's not specifically designed for ultrasonics. The cheapest thing I've found for testing if you're getting some amount of ultrasonic signal up to 100kHz is a short spray from a can of computer dusting gas, but it varies hugely depending on a number of factors including how much gas is left in the can. Lately I've been using one of those pesticide-spraying bottles with a manual pump on it and running it dry with only air inside ¡ª this allows me to produce a long hiss of the same pressure for multiple tests.
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Of course this also produces an unknown frequency response, but by shooting-out against a "flat" acoustics measurement mic and a CO-100k, I can use the calibration data of each mic to get a decent-enough profile of the frequency response of my noise source. This is the best I can do for the moment, but it's accurate enough for ballpark figures, so that when I do eventually pay for fancy sound lab measurements it will be giving me detailed data I can use for small tweaks in my design.
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In terms of electret capsules, the best I've found so far is the Primo em258, but this has a pretty steep upper frequency rolloff, so your SNR at 100kHz is more than 40dB worse than it is at 20kHz, but even a Simple P48 build with this is going to give you access to frequencies that no regular studio mics will.
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Re: How to implement SimpleP48 with PUI 5035 three-pin design?
Hi, I¡¯m interested in using the same mic capsule with the SimpleP48. Did you manage to get it working in the end? If so, would you be willing to share your wiring diagram? Thanks!
One option is Jerry's 'Marcel mod' in Fig4 and p11 of SimpleP48.pdf, latest version
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Another is RENE¡¯S CHARGE AMP (SimpleP48RCA) on p12.? This will be slightly quieter than the 'Marcel mod'.
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, what resistor values did you end up with?
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Re: How to implement SimpleP48 with PUI 5035 three-pin design?
Hi, I¡¯m interested in using the same mic capsule with the SimpleP48. Did you manage to get it working in the end? If so, would you be willing to share your wiring diagram? Thanks!
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Re: Learning more - Ultrasonic Microphone building
For the rich people among us:
Look at the MKE342E capsule from Microtech Gefell
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Re: Learning more - Ultrasonic Microphone building
On Sat, Dec 28, 2024 at 04:06 PM, <soundwichartist@...> wrote:
Thank you so much for this, I had come across MEMS before but was honestly unsure about the best practices to use them. I assume its in best practice to create a PCB for them? I know for sure that would be the best case scenario for 3d printing a case for it, but is there anything else I should know about these types of microphones? I realize there is one ready and make on mic boosters, but its not really the mic shape im going for in my working prototype, so i'm definitely up for learning a little more about PCB design with an experienced friend I have.
The basic micboosters capsule is very tiny and (almost) impossible to work with by hand!?
However, if you're going for a PCB you will need to create a surface mount style board, to accomodate that capsule.... That's quite brave for a first try, IMHO!
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One thing I have discovered (the hard way!) is that MEMs capsules really don't like excessive voltage applied to them..... Keep it below 3 volts, to be safe.?
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I've use a MEMs capsule in the prototype boom pole mounted? mic that? I used this last summer - in conjunction with my Zoom F3 recorder - to record bat echo location calls.? That uses the Micbooster's PCB mounted capsule, fitted into a section of 32mm plastic waste pipe, to help keep the weight down on the end of the boom pole.
Some preliminary notes on that project here: https://www.jp137.com/lts/MEMS.Ultrasonic.Interface.pdf
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Re: Learning more - Ultrasonic Microphone building
On Sat, Dec 28, 2024 at 03:45 PM, Ivano Pelicella wrote:
you can use this one:
?
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I'm pretty sure that Dodotronic (along with many other ultrasonic mic manufatureres ) use the Knowles capsules I mentoned earlier: (see here: )? ?
That should give you an idea of the kind of HF frequency perfomance you might expect....
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Re: Learning more - Ultrasonic Microphone building
To be honest, the way I measure ultrasonics might be a little crude. I honestly just attached an ultrasonic transducer to a signal generator, then 3d printed a stand for the mic and transducer to attach it to. I think i'm definitely going to go the MEMS direction, it seems to be the most straight forward way to go about what i'm trying to achieve!
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Re: Learning more - Ultrasonic Microphone building
Thank you so much for this, I had come across MEMS before but was honestly unsure about the best practices to use them. I assume its in best practice to create a PCB for them? I know for sure that would be the best case scenario for 3d printing a case for it, but is there anything else I should know about these types of microphones? I realize there is one ready and make on mic boosters, but its not really the mic shape im going for in my working prototype, so i'm definitely up for learning a little more about PCB design with an experienced friend I have.
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Re: Learning more - Ultrasonic Microphone building
you can use this one:
https://www.dodotronic.com/product/ultramic-384k-evo/
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Re: Learning more - Ultrasonic Microphone building
When it comes to using studio mics for ultrasonic recording - and especially for outdoor nature recording - then I think the Sennheiser MKH8020 would probably be hard to beat ? .....? Extended upper FR to at least 70KHz, and a lot more linear than other mics I've seen recommended for ultrasonics.?
Plus the advantage of 'low Z' RF technology for resistance to outdoor moisture problems.
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The only downside for amateurs like me is the price!?
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On Sat, Dec 28, 2024 at 01:44 PM, Jerry Lee Marcel wrote:
Actually it depends very much on what one expects.
I've done some experiments with ultrasonic response of typical studio mics.
Using cymbals as the source, one finds out there is significant energy detected by many SDC's up to 60kHz. Of course it doesn't really indicate linearity, but the spectrum shows that the actual response goes quite high.
I think the preferred source for ultrasonic measurements is still a spark gap.
Le 28/12/2024 ¨¤ 12:48, Arjay1949 a ¨¦crit?:
On Fri, Dec 27, 2024 at 08:01 PM, Richard Lee wrote:
I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more.
How do you measure mikes up to 40kHz?
?
I too would be interested to learn how soundwichartist makes the appropriate measurements.....?
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I have found that measuring the detailed ultrasonic response of mic caspules is not an easy task, without access to some serious scientific equipment.
The published ultrasonic responses for cheap capsules - like Knowles MEMs and electrets - show a pretty erratic response (See Knowles App note here: )? ?
Even the expensive Sanken? CO-100k model mentioned earlier has a very non-linear HF response (see here: ).
?
I've found applying the ultrasonic output from a suitable generator directly to a piezo audio 'tweeter' - like this one: ? - can give a rough idea of the ultrasonic response of a capsule......
Sadly of course the linearity of that type of transducer at ulrasonic frequencies introduces another unknown to the proceedings!
?
The published ultrasonic response for the Knowles MEMs capsules can be quite useful.
I find a complex response curve like that easier to correct digitally - in post - than it would be trying to build an accurate hardware analogue filter to compensate.
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Re: Learning more - Ultrasonic Microphone building
Actually it depends very much on what one expects.
I've done some experiments with ultrasonic response of typical
studio mics.
Using cymbals as the source, one finds out there is significant
energy detected by many SDC's up to 60kHz. Of course it doesn't
really indicate linearity, but the spectrum shows that the actual
response goes quite high.
I think the preferred source for ultrasonic measurements is still
a spark gap.
Le 28/12/2024 ¨¤ 12:48, Arjay1949 a
¨¦crit?:
toggle quoted message
Show quoted text
On Fri, Dec 27, 2024 at 08:01 PM, Richard Lee wrote:
I've measured up to 40k on the electret mics
that i'm using, which is very nice. but I want more.
How do you measure mikes up to 40kHz?
?
I too would be interested to learn how soundwichartist
makes the appropriate measurements.....?
?
I have found that measuring the detailed ultrasonic
response of mic caspules is not an easy task, without access
to some serious scientific equipment.
The published ultrasonic responses for cheap capsules -
like Knowles MEMs and electrets - show a pretty erratic
response (See Knowles App note here: )?
?
Even the expensive Sanken? CO-100k model mentioned earlier
has a very non-linear HF response (see here:
).
?
I've found applying the ultrasonic output from a suitable
generator directly to a piezo audio 'tweeter' - like this one:
?
- can give a rough idea of the ultrasonic response of a
capsule......
Sadly of course the linearity of that type of transducer at
ulrasonic frequencies introduces another unknown to the
proceedings!
?
The published ultrasonic response for the Knowles MEMs
capsules can be quite useful.
I find a complex response curve like that easier to correct
digitally - in post - than it would be trying to build an
accurate hardware analogue filter to compensate.
|
Re: Learning more - Ultrasonic Microphone building
On Fri, Dec 27, 2024 at 08:01 PM, Richard Lee wrote:
On Fri, Dec 27, 2024 at 10:59 AM, <soundwichartist@...> wrote:
I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more.
How do you measure mikes up to 40kHz?
?
I too would be interested to learn how soundwichartist makes the appropriate measurements.....?
?
I have found that measuring the detailed ultrasonic response of mic caspules is not an easy task, without access to some serious scientific equipment.
The published ultrasonic responses for cheap capsules - like Knowles MEMs and electrets - show a pretty erratic response (See Knowles App note here: )? ?
Even the expensive Sanken? CO-100k model mentioned earlier has a very non-linear HF response (see here: ).
?
I've found applying the ultrasonic output from a suitable generator directly to a piezo audio 'tweeter' - like this one: ? - can give a rough idea of the ultrasonic response of a capsule......
Sadly of course the linearity of that type of transducer at ulrasonic frequencies introduces another unknown to the proceedings!
?
The published ultrasonic response for the Knowles MEMs capsules can be quite useful.
I find a complex response curve like that easier to correct digitally - in post - than it would be trying to build an accurate hardware analogue filter to compensate.
|
Re: Learning more - Ultrasonic Microphone building
On Fri, Dec 27, 2024 at 10:59 AM, <soundwichartist@...> wrote:
I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more.
How do you measure mikes up to 40kHz?
|
Re: Learning more - Ultrasonic Microphone building
As Underwood suggests in his post, the ultrasonic response of some MEMS mic capsules can be quite good ...... Certainly better than most electrets in my experience.
The capsule in this unit from Micboosters :
wiil give a useful response up to around 100KHz. .... It is that capsule that gets used in many commercial bat detectors.
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You can buy just the capsule without the PCB mount - but it's very tiny and difficult to work with manually ....
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Re: Learning more - Ultrasonic Microphone building
Lots of cheap MEMS mics go higher than 40k.
Am Fr., 27. Dez. 2024 um 19:59?Uhr schrieb soundwichartist via <soundwichartist= [email protected]>:
Learning more about building ultrasonic microphones, I posted a while ago about ultrasonic electret mics. I've found the advantages of them for sure, being nice and easy. learning more and more though, I'm looking for something that gets up to 100k, like the oh-so expensive Sanken CO-100k. I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more. does anyone offer capsules that have that sort of response? If not, what are the other options for achieving this high of a response? Is the only option to build them myself? As a sound designer, I'm looking to capture the largest amount of frequencies possible.?
Thank you again, you incredibly knowledgeable people!?
-Soundwich
|
Learning more - Ultrasonic Microphone building
Learning more about building ultrasonic microphones, I posted a while ago about ultrasonic electret mics. I've found the advantages of them for sure, being nice and easy. learning more and more though, I'm looking for something that gets up to 100k, like the oh-so expensive Sanken CO-100k. I've measured up to 40k on the electret mics that i'm using, which is very nice. but I want more. does anyone offer capsules that have that sort of response? If not, what are the other options for achieving this high of a response? Is the only option to build them myself? As a sound designer, I'm looking to capture the largest amount of frequencies possible.?
Thank you again, you incredibly knowledgeable people!?
-Soundwich
|
Re: Active noise cancelling for microphones in noisy environments - techniques?
I thought I'd provide an update to all of this...
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I decided to focus on the General Aviation scenario because I do that more often. I wanted active noise cancelling headphones and microphone but was too cheap to pay the ?1200 for a Bose A20. I had looked at aviation clip on mics (Uflymike / nflightmic etc), but these all seem to be single unidirectional capsules, plus nobody had them in stock.
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The aircraft I fly uses a Garmin GNC255. This has inputs for two microphones. It supplies about 10V bias voltage on the ring of a 3 pole jack, which also serves as the audio input. It can only supply up to about 10mA.
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I first played around with a few PCB modules:
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1) AN-93 digital signal processing dual microphone (from AliExpress)
- Uses two electret microphones (source and reference)
- Pros:
- Surprisingly good at cleaning up speech
- Cons:
- Only worked with the specific (omni) FET electrets that were provided, refused to work with unidirectional FET electrets, even matched pairs with similar sensitivity
- Kit is designed for conference call environments: The stock electrets were prone to clipping when speaking at close proximity.?
- Current draw ~12mA, possibly too high to run off bias supply
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2) JRL-21 digital signal processing single microphone (from AliExpress)
- Uses one electret microphone, cleans it up digitally
- Pros:
- Good at cleaning up speech, would take a variety of electret mics
- Cons:
- Really annoying ~80ms processing delay which makes it hard to speak at a normal speed given you can normally hear your own mic in your headphones
- Current draw ~20mA, too high to run off bias supply
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So I ended up building a variant of the OPA Alice as suggested by Kennjava, but designed to work with the typical 8-20V bias voltage found in aviation radio units:
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?
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The mics were knock-off Primo-style unidirection FET-less electrets. One facing the pilot, the other a bit further up the boom arm facing away.??
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I did originally put a polarity protection diode between the ring and R7, but the extra 0.6V drop was enough to take the OPA1642 down into its noisy territory. Removing this fixed the problem.
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Certain specs were very hard to dig up:
- Typical General Aviation mic sockets take a PJ-068 5.23mm three pole jack, quite hard to find
- Mic jack pinouts:?
- Tip: "Push to transmit", connect to ground to trigger TX
- Ring: bias voltage + audio input
- Sleeve: connects to radio's ground (radio is then connected to the common grounding point on the aircraft chassis to avoid ground loops)
- Bias voltage in aviation mics: 8-20V
- Max current on bias: 10mA
- Mic input level: 70mV RMS - 1000mV RMS
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The radio has an input gain which is a bit of a faff to set buried through menus, and as this is a shared aircraft, I didn't want to mess the settings up for everyone else who uses it who tend to use Pooleys headsets. Hence the 10k pot in case I needed to trim my? mic output a bit.
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I decapitated an old cheap clip-on Maplin pop-filter to borrow its gooseneck and clip, and then put the high impedance part of the circuitry (R3, R4, C1, R1, R2, mics, R6, OPA1642) on a small PCB at the end of the gooseneck, enclosed in aluminium mesh. The mic capsules are mounted to the PCB on strips of foam without blocking the rear holes, with thin enamelled copper wire feeding them to try to mechanically decouple them from the PCB and thus each other. I then ran a shielded 2 core cable up the gooseneck to a second PCB mounted in a small shielded enclosure stuck to the outside of the clip. This second PCB has a finger-friendly rotary knob for the pot. I slid a foam windbreak over the aluminum mesh enclosed PCB to kill plosives.
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For headphones, I used a pair of Bose QuietComfort SCs. The mic set clips onto the headband just above the left earpiece. I chose the QuietComfort because if the internal battery gets depleted, it just falls back to being a passively noise-cancelled set of headphones.??
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It works pretty well! Happens to be at the right mic level with the pot mostly towards zero. It is a little tinny, which is to be expected because of how unidirectional capsules are less directional at the bass end, but definitely picks up much less engine noise than the Pooleys headsets. The clip and gooseneck are sturdy and don't flap around at all. There's enough clearance between the headband and my head just above the earphone cup, so that the clip doesn't touch my head at all. The Bose QuietComfort headphones are very comfortable to wear for hours.
My only regret is using a 3.5mm jack socket as the PCB input. This has come out a couple of times, killing the mic, when turning my head to look out the right window if my shoulder has sandwiched the main feed cable between me and the seat.
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I now have a set of active noise cancelling headphones with microphone for aviation use for <?280, plus the fun of putting it together!
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Zander
Ivano Pelicella
underwood
