RAM SODIMMs make acoustic noise.. does this make sense?

[Milos]

Hi all,

I just noticed that my RAM SODIMMs make a high-pitched acoustic noise that sounds just like data being saved to a hard drive but higher pitch (I would guess 30-40kHz - i.e. above high-pitched violin, but interrupted like a bit stream).

This doesn't make sense to me since audible range is a few Hz to about 40kHz, while memory runs at >100MHz. Yet opening the machine, it is pretty clear that the noise is directly from the RAM chips (both -- one 256MB IBM, one 512MB Crucial) or perhaps something under them but the latter's unlikely.

I see a bit of comment on a similar matter here: http://forum.thinkpads.com/viewtopic.ph ... =ram+noise

Anyone have any thoughts on the source of such noise? I haven't tried reseating the RAM modules.

Milos

[alexzabr]

, officially accepted audiable frequency range is 20Hz - 20kHz, whilst in real life very few people can brag having such broad listening frequency range, most are limited from about 60-80Hz to about 13-15kHz. So if you can hear it, it must be within 20kHz range.

[rkawakami]

From my experience, the sounds like you describe coming from electronic equipment is due to high voltage transformers and inductors (think of TVs and CRTs that whistle at around 15kHz). I do not believe that those parts are on any SODIMMs. Memory chips, resistors and capacitors are the norm. However, I suppose that it is possible for a 'loose' mechanical connection to resonate given enough electronic signal switching. Removing the SODIMMs, cleaning the contacts and re-seating them does sound (no pun intended) like a good place to start.

About the only other thing inside a laptop that could be the source of the noise is the inverter board for the LCD as mentioned in the thread you referenced. I use an A31 at work as my main computer. I will try to give it a listen with my near "half a century ears" (as my teenage daughters LOVE to point out) next week. But I don't think that I could hear it even if it is there. Too many Who and Grateful Dead concerts over the years took care of that .

[GomJabbar]

But I don't think that I could hear it even if it is there. Too many Who and Grateful Dead concerts over the years took care of that .

"Ain't it the truth, ain't it the truth!"

[Milos]

From my experience, the sounds like you describe coming from electronic equipment is due to high voltage transformers and inductors (think of TVs and CRTs that whistle at around 15kHz). I do not believe that those parts are on any SODIMMs. Memory chips, resistors and capacitors are the norm. However, I suppose that it is possible for a 'loose' mechanical connection to resonate given enough electronic signal switching.

Ok, one reliable way that I can get the sound/squeal is using PC Doctor for Windows and running CPU Test under Diagnostics.

When the Level 2 Cache is being tested, the squeal is on, and each bit pattern (0x0F0F0F0F, 0xF0F0F0F0, 0x01010101, etc) has a different pitch squeal (well, there are only a couple of pitches, or all are similar, and they change as the bit pattern changes). It's like stepping through a piano octave, but in random order.

Actually in that case, I checked and the humm is coming from the CPU area (left corner near LCD), not the RAM area (opened hatch underneath laptop on left side, under keyboard). Actually, I can't find a reliable way to get the SODIMM humm to happen yet - I'm pretty sure I checked it was from there though it's the same sound as the "L2 cache humm" described above.

About the only other thing inside a laptop that could be the source of the noise is the inverter board for the LCD as mentioned in the thread you referenced.

It is definitely not the LCD -- it's true that sound gets guided around the case and you can sometimes hear the hard drive seemingly from totally the opposite corner, but the LCD inverters are too far to be causing this humm..

Milos

[rkawakami]

<snip>... each bit pattern (0x0F0F0F0F, 0xF0F0F0F0, 0x01010101, etc) has a different pitch squeal (well, there are only a couple of pitches, or all are similar, and they change as the bit pattern changes). <snip>
Actually in that case, I checked and the humm is coming from the CPU area (left corner near LCD), not the RAM area (opened hatch underneath laptop on left side, under keyboard).

This is very familiar to me. A DRAM memory tester that I used to program several years ago would "sing" during the part of the test which exercised the memory in the "fast page mode". It was running at 25Mhz (the limit of the tester) in that mode whereas the other functional tests were around 7 or 8Mhz and didn't generate any noise. I'm pretty sure that the inductors inside the tester (not the memory itself) was the cause. It is probably the same thing happening in your A31.

It isn't something that I would worry too much about. You'd have to open up the system and use a stethoscope to pinpoint the offending part and then either re-solder it to the motherboard or use something non-conductive to keep it from vibrating (hot glue?).

I've run PC Doctor numerous times with my 600X and T2x systems and don't recall ever hearing any singing. I'll try the A31 at work next week and let you know what I find. I'll enlist younger ears just to be sure .

[rkawakami]

Okay, I've run the PC Doc CPU test and confirmed that I hear "singing", along with some younger ears. So this may be a "feature" for some systems. It's not very loud on my A31 but it is there. It sounds exactly like the series of tones that the tester I referenced above made. I can't tell exactly where it is coming from though. Oh yeah, for your info I have a 1.6Ghz A31with 1G of memory.

[doppelfish]

Okay, I've run the PC Doc CPU test and confirmed that I hear "singing", along with some younger ears. [...]

So, can you play songs on it?

scnr,
-- fish

[christopher_wolf]

You know what this makes me think of?

Back in the ancient (in computer terms) days where ferrite core memory systems were all the rage. You could tune into certain, higher, frequencies they emitted with a transistor radio. Some programmers, mostly in academic institutions (this takes a good deal of leisure time! ), had a game akin to "Name that Tune" where they would code out memory access I/O ops and see if they could get it to play a recognizable tune when they listened in.

[Milos]

This is very familiar to me. A DRAM memory tester that I used to program several years ago would "sing" during the part of the test which exercised the memory in the "fast page mode". It was running at 25Mhz (the limit of the tester) in that mode whereas the other functional tests were around 7 or 8Mhz and didn't generate any noise. I'm pretty sure that the inductors inside the tester (not the memory itself) was the cause. It is probably the same thing happening in your A31.

Ray, thanks for the anecdote and for verifying the buzz. I wasn't worried, just curious - and still am.. Why would an inductor operated at e.g. 25MHz vibrate at such low (acoustic) frequencies? What are inductors (whose excitation would depend on the bit pattern) used for near RAM chips? (Maybe for resonating the bus clock? Or the reverse.. some kind of RF choke for the power supply? But neither of those two is consistent with being bit pattern dependent..)

Milos

[rkawakami]

But neither of those two is consistent with being bit pattern dependent..

I would disagree with you on that point. From a circuit design standpoint, the worst possible condition you can throw at a memory device is an alternating "all high" to "all low" output state. Envision 32 (or 64) output pins in a memory array changing from one cycle to the next (say every 10ns, i.e. 100Mhz) by going high and then low. This is the maximum current draw condition and will cause a greater amount of switching 'noise' on the power supply lines as the power supply attempts to keep up with the current demand than any other random bit pattern across the output pins.

That the audible noise is coming from an RF choke is also possible I suppose. Anything that acts like a transformer or coil could resonate to generate a sound that you could hear.