Crackling microphone

when configuring the microphone with the following settings:
http://www.upload.ee/files/5692058/asound.state.html
When you try to record sound from a microphone (such as: gst-launch-0.10 alsasrc device=“hw:1,0” num-buffers=300 ! qtmux ! filesink location=this.mp4) appears quite audible crackling.
Here is an example of the resulting file
http://www.upload.ee/files/5692050/this.mp4.html

In a typical computer the same microphone works almost without crackling.
How can this problem be solved?

I hear a pop at the very start (normal at startup), but then I hear some background noise during play. Is the sound during play what is at question?

If so, it may be the sound is from a fan. Not necessarily the physical noise, but possibly the power bus produces noise near the audio. In the case of attaching an external hard drive via SATA, I’ve noticed this in particular does cross-talk onto the analog audio.

Do you have any kind of hard drive attached? Is the microphone anywhere near the fan or power?

Yes, means background noise.
Yes, it’s possible, it’s the sound of the fan, but too much it affects the crackling.
Here, for example, a record with the same microphone, but with local computer. Here such strong “crackle” is not observed
http://www.upload.ee/files/5693981/this2.mp4.html

Or, maybe there is some gstreamer filter, which will remove this noise?

It really sounds like power rail noise which in turn would mean the fan (not the fan’s physical air movement against the microphone, but the electrical noise). I would not recommend removing the fan power connector when throttling is disabled, but you could run a short test with the power connector to the fan being removed, and see if the recorded audio has changes in noise. The case where I’ve had noise during SATA drive operation was also power rail noise, but the spin-up of the SATA drive is very smooth and distinct (the fan might change tone if the fan changed loads).

No, it is certainly not because of the noise. More precisely, perhaps, because of it, but it should not create interference. Specifically I tried to remove the microphone away from the system unit, and the result is the same: jetson have interference, but local сomputer - no

Were you able to test with fan power plug disconnected? EM noise is the reason for testing this, not because of mechanical noise. The traces on the circuit board can be routed closely together even on unrelated circuits and cross talk onto the microphone traces…or the power supply to microphone circuits can be modulated by power changes of the fan load. With the fan plug disconnected for a few seconds you can verify if those issues go away or not (and the fan is an inductive load, so this really needs to be the first thing tested).

Ah, sorry! I misunderstood the previous message.
However, when you turn off the fan in Jetson, noise is also observed.
More (except power, Ethernet and microphone) is not included in it.
Noise character itself has changed quite a bit (maybe, not changed at all).

I tried to off ethernet cable. Noise character has really changed, is “faster”. But the power has remained the same

From what you said I’m unsure of whether the fan disconnect changed or did not change the nature or strength of the noise. Basically though, you are testing for two things…cross-talk and power source noise (it is possible that both occur in some mix). Distinguish between strength of noise and other qualities, like frequency or spectrum of noise (strength versus quality).

Removing a noisy power consumer (e.g., an inductive motor load) should reduce strength of noisy power delivery since this is essentially a load modulating power rails and the load is removed. Cross-talk would tend to remain after removing the fan load if the power rail modulation is not the issue since non-power circuits would be responsible.

Ethernet cable does not significantly change power rail load, so changes in Ethernet cable changing noise character would tend to lean towards cross-talk. Fan disconnect leading to change in nature of the noise without any reduction of noise would also tend to lean towards cross-talk. In the case of power noise you can adjust components, typically capacitor values or type of capacitor. In the case of cross-talk, typically it would mean re-arranging trace shapes and locations (in wires that means twisted pairs and shielding changes).

The microphone wire itself can be (and usually is) a very significant contributor towards cross-talk (in this case cross-talk with environment outside of Jetson). I think the connector is capable of detecting if a microphone is plugged in or not, so continuing to record without a microphone as if the microphone were present may not be easy. The goal of testing with no microphone but with everything else active and recording is to see how much of the noise is from JTK1 circuitry and how much is from the microphone. What you would have to do is to wire a small plug with the same connector as the microphone and put a pure resistance across as a fake microphone load…the shorter the cable the better. With that you could tell if the noise still exists without the microphone.

I do not know what impedance the JTK1 wants for a microphone, but noise from cross-talk of the microphone itself may go up if the actual microphone impedance differs too far from what the design calls for.

Yes, when you insert a short cable, the noise disappeared almost completely

If you are sure that record function was still on with the short cable, then you just verified the microphone cable was at fault. Very likely the cable is not shielded and maybe does not even use twisted pair. If there is an active pre-amp inside the microphone, then this could also generate noise (most microphones do not have this).

This is going to sound a bit silly, but as a partial test of noise pickup from the outside world you could wrap the entire cable and microphone in aluminum foil and ground the foil. I suspect just holding a wire or alligator clip to the foil and the 9-pin D-sub shell connector ground (the D-shaped metal part is the shell ground) would suffice. You could further verify outside environment noise pickup that way, versus microphone internal noise generation.

FYI, when I’m doing critical work with RFI getting in the way I always use quad shield cables. Very few microphones come with that level of shield unless it is a studio microphone.