Ultrasonic Recording

Did you buy a new mixer? Do you need advice? Post here.
Forum rules
If you require help using Audacity, please post on the forum board relevant to your operating system:
Windows
Mac OS X
GNU/Linux and Unix-like
mglynch
Posts: 11
Joined: Sun Apr 04, 2021 2:42 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by mglynch » Mon Apr 05, 2021 8:14 pm

steve wrote:
Mon Apr 05, 2021 2:38 pm
mglynch wrote:
Mon Apr 05, 2021 2:24 pm
Any ideas on how I can get a decent inexpensive interface that will power the mic and pass the audio through to the computer or recorder?
You may be able to get help here: https://forum.pjrc.com/threads/38988-Bat-detector/
Interesting thread. Thanks for the link.

DVDdoug
Forum Crew
Posts: 9296
Joined: Fri Sep 10, 2010 11:30 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by DVDdoug » Mon Apr 05, 2021 8:35 pm

I am hoping that the line-in is sufficient, w/o a pre-amp, for recording and for computer analysis. That is one part of my question. If I put an XLR connector or Headphone jack directly on the microphone audio line, will this be sufficient...
Microphones require a preamp and your TASCAM recorder has a built-in preamp.

Microphone signals are in the ballpark of 10mV depending on the loudness of the sound and the sensitivity of the microphone. Of course it varies a LOT so interfaces & recorders always have a recording-volume control. If you have an idea of the SPL level you can estimate the voltage from the microphone specs. But I assume SPL is unknown? 1Pa = 94dB SPL and 0dBV is 1 Volt. ...If you can handle MATLAB I assume you can calculate dB.

Line level signals (RCA outputs from a CD/DVD player or TV) are about 1V, again depending on "loudness", etc. These can usually go directly into an analog-to-digital without a preamp. Headphone signals are in the same ballpark and compatible with line-level signals. The difference is headphone outputs are capable of driving lower impedance loads.

mglynch
Posts: 11
Joined: Sun Apr 04, 2021 2:42 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by mglynch » Mon Apr 05, 2021 10:38 pm

DVDdoug wrote:
Mon Apr 05, 2021 8:35 pm
I am hoping that the line-in is sufficient, w/o a pre-amp, for recording and for computer analysis. That is one part of my question. If I put an XLR connector or Headphone jack directly on the microphone audio line, will this be sufficient...
Microphones require a preamp and your TASCAM recorder has a built-in preamp.

Microphone signals are in the ballpark of 10mV depending on the loudness of the sound and the sensitivity of the microphone. Of course it varies a LOT so interfaces & recorders always have a recording-volume control. If you have an idea of the SPL level you can estimate the voltage from the microphone specs. But I assume SPL is unknown? 1Pa = 94dB SPL and 0dBV is 1 Volt. ...If you can handle MATLAB I assume you can calculate dB.

Line level signals (RCA outputs from a CD/DVD player or TV) are about 1V, again depending on "loudness", etc. These can usually go directly into an analog-to-digital without a preamp. Headphone signals are in the same ballpark and compatible with line-level signals. The difference is headphone outputs are capable of driving lower impedance loads.
Well, bat calls can exceed 140dB SPL at 0.1 meter, but the bats I'm recording are free-flying, they are facing random directions at varying distances, and rarely less than a few meters. And ultrasound intensity drops off much faster than audible frequencies, the higher the frequency the more rapid the attenuation as a general rule. ie about 0.7dB/meter at 30kHz up to 3dB/meter at 100kHz. I'm typically looking at about 60kHz calls, but some go as high as 120kHz or so.

I'm not sure I understand how to calculate the voltage from the spec. The sensitivity says "-53dB ±3dB @ 74dB SPL". So, I think the sensitivity is at 74dB rather than the standard 94dB? And this is presumably at 1kHz, there is a drop in sensitivity at ultrasonic freqs, according to Knowles. Anyway, I think there are too many unknown variables here for the calcs to be useful.

So, I guess the answer here is that it may work without a preamp, but I might want a preamp to adjust the level for more distant targets, for targets not facing my direction, etc. I sent an e-mail to Knowles about going without a pre-amp, hopefully I'll get a response. At any rate I plan on trying it and seeing how it goes.

Thanks again for the input!

steve
Site Admin
Posts: 80816
Joined: Sat Dec 01, 2007 11:43 am
Operating System: Linux *buntu

Re: Ultrasonic Recording

Post by steve » Mon Apr 05, 2021 11:24 pm

mglynch wrote:
Mon Apr 05, 2021 10:38 pm
I'm not sure I understand how to calculate the voltage from the spec. The sensitivity says "-53dB ±3dB @ 74dB SPL". So, I think the sensitivity is at 74dB rather than the standard 94dB? And this is presumably at 1kHz, there is a drop in sensitivity at ultrasonic freqs, according to Knowles. Anyway, I think there are too many unknown variables here for the calcs to be useful.
Perhaps this will help: https://www.analog.com/en/analog-dialog ... ivity.html#
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

kozikowski
Forum Staff
Posts: 68990
Joined: Thu Aug 02, 2007 5:57 pm
Operating System: macOS 10.13 High Sierra

Re: Ultrasonic Recording

Post by kozikowski » Tue Apr 06, 2021 12:04 am

There's another fuzzy rule here. The noise in a system is determined by the first electronics that the microphone signal hits. It will never get better than that without extraordinary gymnastics.

A line-in connection might have a noise floor of about -60dB with a show volume of about -6dB. That's perfectly ordinary. If you apply your microphone signal of -53dB to that, your bats and the Line-In noise level are about the same volume.

So somewhere in the SHSHSHSHSHSHSH spring rain in the trees sound is your bat chat.

And that's if everything goes well. Did we cover how you're going to supply battery to the amplifier in the microphone? There is a tiny transistor up there and it needs juice from somewhere.


The XLR connection is not magical, although it seems that way. Look closely at the connector. Pin 2 has the performance electrically right-side up. Pin 3 has the identical performance upside down. Pin 1 is the protection braid/shield wound around everything.

The XLR receiver/preamp only looks for a difference between 2 and 3. Hum, interference, buzz, and other electrical trash appear the same on both 2 and 3 and within reason are completely ignored. That gives you an XLR rock band microphone playing into the audience sound mixer 125 feet away with perfect fidelity and no noise. I'm not making that up.

It is possible to connect pin 3 and 1 together and send a signal down pin 2. That's a simple unbalanced to balanced converter. You give up much of the buzz and trash management and long distance cables, but that does work.

The question is how you're going to do that without a soldering iron and the skills to use it. That's the same skillset needed to connect your microphone to anything.

Koz

mglynch
Posts: 11
Joined: Sun Apr 04, 2021 2:42 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by mglynch » Tue Apr 06, 2021 3:48 am

kozikowski wrote:
Tue Apr 06, 2021 12:04 am
There's another fuzzy rule here. The noise in a system is determined by the first electronics that the microphone signal hits. It will never get better than that without extraordinary gymnastics.

A line-in connection might have a noise floor of about -60dB with a show volume of about -6dB. That's perfectly ordinary. If you apply your microphone signal of -53dB to that, your bats and the Line-In noise level are about the same volume.

So somewhere in the SHSHSHSHSHSHSH spring rain in the trees sound is your bat chat.

And that's if everything goes well. Did we cover how you're going to supply battery to the amplifier in the microphone? There is a tiny transistor up there and it needs juice from somewhere.


The XLR connection is not magical, although it seems that way. Look closely at the connector. Pin 2 has the performance electrically right-side up. Pin 3 has the identical performance upside down. Pin 1 is the protection braid/shield wound around everything.

The XLR receiver/preamp only looks for a difference between 2 and 3. Hum, interference, buzz, and other electrical trash appear the same on both 2 and 3 and within reason are completely ignored. That gives you an XLR rock band microphone playing into the audience sound mixer 125 feet away with perfect fidelity and no noise. I'm not making that up.

It is possible to connect pin 3 and 1 together and send a signal down pin 2. That's a simple unbalanced to balanced converter. You give up much of the buzz and trash management and long distance cables, but that does work.

The question is how you're going to do that without a soldering iron and the skills to use it. That's the same skillset needed to connect your microphone to anything.

Koz
DVDdoug suggested using a 1.5 volt battery to power. I think that is worth a try.

I expect that to be the case, that the call is below the noise floor, but I think I need to try first to see.

Why is anyone still soldering in the 21st century? Oh, that's a rhetorical question, no need to reply. I expect I can crimp with Neutrik connectors, at least I hope I can.

steve
Site Admin
Posts: 80816
Joined: Sat Dec 01, 2007 11:43 am
Operating System: Linux *buntu

Re: Ultrasonic Recording

Post by steve » Tue Apr 06, 2021 9:31 am

mglynch wrote:
Tue Apr 06, 2021 3:48 am
I expect I can crimp with Neutrik connectors, at least I hope I can.
Because microphones use such low level signals, I would recommend soldering crimp connectors rather than relying on the crimping. Crimp + solder is much more reliable than just crimp (and very easy to solder a crimped connector).

More commonly Neutrik plugs have "bucket" connectors (an indentation in the end of each pin). These are not fun because you need a lot of heat so that the solder melts in the bucket, but not too much or the plastic holding the pin will melt.

An easy to use alternative to soldering Neutrik plugs is to get leads that already have the plugs, cut the leads, and solder the leads instead of soldering the plugs. While experimenting with hardware designs, you can "twist and tape" the wires instead of soldering, but don't rely on that for long term use.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

mglynch
Posts: 11
Joined: Sun Apr 04, 2021 2:42 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by mglynch » Tue Apr 06, 2021 11:48 am

steve wrote:
Tue Apr 06, 2021 9:31 am
mglynch wrote:
Tue Apr 06, 2021 3:48 am
I expect I can crimp with Neutrik connectors, at least I hope I can.
Because microphones use such low level signals, I would recommend soldering crimp connectors rather than relying on the crimping. Crimp + solder is much more reliable than just crimp (and very easy to solder a crimped connector).

More commonly Neutrik plugs have "bucket" connectors (an indentation in the end of each pin). These are not fun because you need a lot of heat so that the solder melts in the bucket, but not too much or the plastic holding the pin will melt.

An easy to use alternative to soldering Neutrik plugs is to get leads that already have the plugs, cut the leads, and solder the leads instead of soldering the plugs. While experimenting with hardware designs, you can "twist and tape" the wires instead of soldering, but don't rely on that for long term use.
Sounds good. I will probably ask one of the techs at work to do the final soldering for me. That's what they do for a living.
As soon as I figure out what to use as a housing I think I'm ready to start experimenting with designs.
Thanks for your help!

kozikowski
Forum Staff
Posts: 68990
Joined: Thu Aug 02, 2007 5:57 pm
Operating System: macOS 10.13 High Sierra

Re: Ultrasonic Recording

Post by kozikowski » Tue Apr 06, 2021 5:56 pm

Why is anyone still soldering in the 21st century?
Why is someone trying to build a microphone from parts in the 21st Century.

I think I left my skycar double parked.

Screen Shot 2021-04-06 at 10.52.51 AM.png
Screen Shot 2021-04-06 at 10.52.51 AM.png (536.33 KiB) Viewed 213 times

Koz

mglynch
Posts: 11
Joined: Sun Apr 04, 2021 2:42 pm
Operating System: Windows 10

Re: Ultrasonic Recording

Post by mglynch » Tue Apr 06, 2021 6:51 pm

kozikowski wrote:
Tue Apr 06, 2021 5:56 pm
Why is anyone still soldering in the 21st century?
Why is someone trying to build a microphone from parts in the 21st Century.

I think I left my skycar double parked.


Screen Shot 2021-04-06 at 10.52.51 AM.png


Koz
:lol:

Exactly, why are we still soldering and not driving sky cars in the 21st Century. And you'd think we would have built everything by now and not have to build anymore. I mean, what, 6000 years of civilization and we haven't built everything yet?

But just look at the mark-up on these when put in a housing with a cable and connector. Like $50 in materials is going for $600 - $1500. And I am learning quite a bit in the process.

Anyway, Knowles got back to me. Here is what they said:

"You can use a mic level input to a computer sound card. If you want to power the mic from the sound card, add 2.2k resistor from output to negative. Then wire to 3.5mm stereo audio plug, positive = tip, negative = sleeve."

Post Reply