archie456
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Hiss coming from Pi2

Thu Mar 05, 2015 8:41 am

Hi,

I have a Raspberry Pi2 which I use to run OpenElec media centre - all works really well and I'm very pleased.

Except, there is a hissing sound coming from the Pi - the sound seems to be coming from the board itself and changes pitch a little depending on what the Pi is doing.

I've plugged everything except the power and the hiss is still there, its certainly not coming from the TV.

I'm wondering if this is a fault? Has anyone else had this issue?

Thanks.

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RaTTuS
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 8:45 am

can you record it ?
is it a grounding problem - ground the RPi to earth
if it is coming from the RPi with no power then there may be gremlins arround
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 8:47 am

I think that pythons are more likely than gremlins.
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 9:34 am


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PeterO
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 9:40 am

archie456 wrote:Hi,
I've plugged everything except the power and the hiss is still there, its certainly not coming from the TV.
"plugged" or "unplugged" ?

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archie456
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 1:17 pm

Yes - sorry - l meant unplugged everything.

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Re: Hiss coming from Pi2

Thu Mar 05, 2015 7:09 pm

Is it coming from the power supply? Cheap and nasty power supplies often make hissing noises which change depending on the ammount of load placed on them.

I guess the same could be happening with the switched mode converters on the pi itself. Especially if an inductor is not mounted as solidly as it should be.

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eriktheitalian
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 10:06 pm

Pls show situation with video record tube.
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azerty
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Re: Hiss coming from Pi2

Thu Mar 05, 2015 10:17 pm

It could be piezoelectric effect affecting the ceramic input capacitors of the Pi's onboard switching power supplies. Audible noise means the wallwart has a low switching frequency (kilohertz range), which means it would also have relatively large voltage ripple, which is doubly bad in terms of audible noise.
The onboard switching supply is less likely to be a culprit. For inductors of that size the switching frequency is typically in the megahertz range, well out of the audio band.

archie456
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Re: Hiss coming from Pi2

Fri Mar 06, 2015 8:20 am

This link is a recording of the sound.

Its not that easy to hear, its the buzz thats audible throughout this recording, but with the background noise its difficult to hear.

https://drive.google.com/folderview?id= ... sp=sharing

In a room with noise its unnoticeable, but in a quite room its easily to hear - I was thinking of using the Pi2 in our bedroom - but not with this noise.

RaTTuS - Whats the best way to ground the Rpi2 to try your test?

Plugwash - its definitely not the power supply...

Azerty - I've no idea what any of that means, is it fixable?

I assume, by the replies to this topic I'm the only one experiencing this, and its not a common issue - in that case I guess I should RMA it and new a new one.

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eriktheitalian
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Re: Hiss coming from Pi2

Fri Mar 06, 2015 4:23 pm

archie456 wrote:This link is a recording of the sound.

Its not that easy to hear, its the buzz thats audible throughout this recording, but with the background noise its difficult to hear.

https://drive.google.com/folderview?id= ... sp=sharing

In a room with noise its unnoticeable, but in a quite room its easily to hear - I was thinking of using the Pi2 in our bedroom - but not with this noise.

RaTTuS - Whats the best way to ground the Rpi2 to try your test?

Plugwash - its definitely not the power supply...

Azerty - I've no idea what any of that means, is it fixable?

I assume, by the replies to this topic I'm the only one experiencing this, and its not a common issue - in that case I guess I should RMA it and new a new one.

Are u using analog audio output or hdmi from tv/monitor ?
Hiss coming from directly pi board or speakers ?
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Re: Hiss coming from Pi2

Fri Mar 06, 2015 4:32 pm

I would say almost certainly a faulty board, possibly a thing that will get worse and completely break down later.
If at all possibly, try a very different power supply, it might just be some weird heterodyne mixing going on, but unlikely.


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archie456
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Re: Hiss coming from Pi2

Fri Mar 06, 2015 9:36 pm

I'm connecting to the TV via HDMI.

But if I disconnect all plugs apart from the power the noise is still made, so I know its not the TV.

I agree, I think its a fault board.

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Re: Hiss coming from Pi2

Fri Mar 06, 2015 9:43 pm

That's why you wait a few months to buy one to make sure the faults are worked let the guys who have lots of time and money and patience to report the bugs so the foundation can release a more stable version
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eriktheitalian
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Re: Hiss coming from Pi2

Sat Mar 07, 2015 12:17 am

archie456 wrote:I'm connecting to the TV via HDMI.

But if I disconnect all plugs apart from the power the noise is still made, so I know its not the TV.

I agree, I think its a fault board.
I'm know (if not fault) hdmi transferring audio with digital data.
If u listen hiss noise from tv speaker. Can be tv incompatibility.

If u listen hiss noise from board. Fault board or maybe your power supply damaged board.
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archie456
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Re: Hiss coming from Pi2

Sat Mar 14, 2015 6:44 pm

OK, got a new Raspberry Pi2 - but, when I plug it in I get the same hiss from the board.

As the hiss still comes from the board with everything unplugged (accept the power) - then I guess it can only be the power supply thats causing it.

Whats strange is that the hiss is from the Raspberry Pi2 and not the power supply which is located about 1m away.

The power supply is:

Model No: PC-052000-1
Input: 100-240v-50-60Hz
Output: 5.25v - 2A.
Bought from: https://www.modmypi.com/
About a year old.

Which from my limited knowledge is well rated for use with a Pi.

The supply worked flawlessly when powering my old Pi1 perhaps the extra draw from the Pi2 is upsetting it...?

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Re: Hiss coming from Pi2

Sat Mar 14, 2015 8:01 pm

I just want to chip in that I get the same from my workhorses RPi 2 - works fine except for the quiet hissy buzzy noise. Volume / pitch varies depends primarily on WiFi load - used the same dongle on previous model B+ workhorse and it was silent. Likewise keyboard and mouse and monitor are same as my previous workhorse Pi B+ that got replaced on the release of the B2. Audio is usually turned off so not that either. I'm using a 2.1A PSU, and the noise is definitely not coming from there - they Pi and PSU are separated by enough distance to differentiate.

As I say, no other symptoms but it does appear to be something on the B2 board itself.
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xoopha
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Re: Hiss coming from Pi2

Sat Mar 14, 2015 10:29 pm

Haha, this is funny.

I've made some tests and I can hear two different sounds coming from my Pi2 board. They are faint, but noticeable when in silence.

One sounds like a crackling, not unlike what a tiny hard disk drive would make, that seems to come from USB activity.
The other sounds like the tiniest steaming teapot, that seems to happen whenever sound is sent through the HDMI port. Executing the default python games (even the ones that have no sound!) will trigger it. And, of course, pushing actual sound through like when listening to online radios will trigger it.

Using CEA versus DMT or overclocking/overvolting versus default speeds/voltage doesn't result in different behavior.

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Re: Hiss coming from Pi2

Sat Mar 14, 2015 11:31 pm

some capacitors can exhibit piezoelectric behavior, that is they can contract/expand according to the electric field (voltage) they are exposed to, but to be discernible to the human ear the frequency of this field must be in the hearable range of 30 to 3000 Hz, most signals are not. Another possibility is inductors, of which coil segments or wires can attract/repel, but the switching power converters of a PI use frequencies far beyond human hearing.

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xoopha
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Re: Hiss coming from Pi2

Sat Mar 14, 2015 11:49 pm

I have tried to record the sounds with my cellphone but they are either too faint to register or the cellphone mike is just that cheap.
By the way, there is a third sound that I didn't mention before: if I turn off the TV while the Pi is running, (the HDMI port?) will make an interference sound, similar to the static noise on a radio, that ceases when the TV is completely off.

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Re: Hiss coming from Pi2

Sun Mar 15, 2015 6:04 am

mandrewpi This will probably not be fixed and many bugs are fixed before the Pi 2B. This is not a widely reported problem so it doesn't need to be fixed. Unlike the Pi 2B's problem with camera flashes because of the u16 that is a minor problem unless you take your Pi 2B to the red carpet. I bought mine and I have had no problems but charging my code to improve with the arm_V7 CPU. Don't worry about with hardware bugs just buy one I did and mine is fine and I run it 24/7 non stop.
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eriktheitalian
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Re: Hiss coming from Pi2

Sun Mar 15, 2015 6:53 pm

rpiswag wrote:mandrewpi This will probably not be fixed and many bugs are fixed before the Pi 2B. This is not a widely reported problem so it doesn't need to be fixed. Unlike the Pi 2B's problem with camera flashes because of the u16 that is a minor problem unless you take your Pi 2B to the red carpet. I bought mine and I have had no problems but charging my code to improve with the arm_V7 CPU. Don't worry about with hardware bugs just buy one I did and mine is fine and I run it 24/7 non stop.
Camera flash issue related about mirrored like equipment near the power input ( micro usb ). Black paint or plastic molten drop can easily block light input. Only cover for mirrored like equipment is enough for fix flash bug.
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Re: Hiss coming from Pi2

Sun Mar 15, 2015 7:40 pm

mahjongg wrote:some capacitors can exhibit piezoelectric behavior, that is they can contract/expand according to the electric field (voltage) they are exposed to, but to be discernible to the human ear the frequency of this field must be in the hearable range of 30 to 3000 Hz, most signals are not. Another possibility is inductors, of which coil segments or wires can attract/repel, but the switching power converters of a PI use frequencies far beyond human hearing.
The capacitors used on Pi B+ / Pi 2 exhibit piezoelectric behaviour. In fact the issue that the OP describes is almost certainly due to MLCCs "flexing" under the applied voltage.

My educated guess is that the PSU used with the Pi 2 has some ripple voltage that is in the frequency of human hearing or the ripple voltage of the PSU is interacting with the switching frequency of the onboard SMPS chips to "mix" into a frequency that's audible.

Solution: use a PSU with less ripple.
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archie456
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Re: Hiss coming from Pi2

Sun Mar 15, 2015 8:31 pm

I used a 2A, 5V power supply that came with my old Blackberry - the Pi2 generated the same noise.

This is really a problem for me, my dream of having a connected media centre in each room which came true with the power of the Pi2 is now hitting a snag as I wont be able to have one in the bedroom - the noise will annoy the wife...

(she's not happy with ear plugs either...)

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Re: Hiss coming from Pi2

Mon Mar 16, 2015 5:39 am

There are many sound proofing materials you could use as or in the RPi case, sure it would be a whole lot bigger though. Or you might try dabbing epoxy on the components.
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