High pitch sound possible ground loop issue?

cclboss · 09-11-2008, 01:42 AM

Hi,

Been driving my M3 E90 for a couple weeks now but I noticed that there appears to be a very subtle high pitch noise that I swear is a ground loop feedback from the audio system. I have brought it back to the dealer and they claim they can't hear it. I understand the M3 engine/exhaust has a higher pitch sound than normal cars but I believe this is coming from the speakers. In normal cars, you can turn off the radio and verify but with the M3, you can only "mute" the audio and the high pitch sound still comes through.

Does anyone else have this problem? Is there an easy way to totally switch off the audio system so I can verify for myself (and the dealer) that there really is a problem? This is very annoying especially on the highway and the car is cruising and there is this high pitch "buzz".

Thanks.

nitramsen · 09-11-2008, 03:25 AM

Hi,

I have the same noise in my E90 but I cannot really determine were the pitch is coming from. Maybe ground loop maybe engine.

Let me known if you figure out were this is coming from as it is really annoying as you say on highway drives.

southlight · 09-11-2008, 05:39 AM

In case you mean a noise coming out of the speakers and only during acceleration I'm interested in the outcome either.

Best regards, south

ZoinksM3 · 09-11-2008, 07:05 AM

Ditto, very fain't whine. I called that the turbo in my first car.

I use an iPOD almost exclusively so I'm wondering if the USB port isn't grounded properly. This was a known issue in my old Lexus which they said they wouldn't fix. I ended up buying a stereo mini-jack ground loop isolator which fixed it. PAC SNI-1 for anybody interested.

I'll try it out and report back. I don't think I'll accept the same story from BMW as from Lexus. Lexus just had a 12v port and a line-in jack. I spent $400 for the iPOD option.

Bronx Cheer · 09-11-2008, 11:08 AM

If you think it is an alternator (ground loop) whine coming from the stereo, there are three ways you might be able to check.

1) see if the sound gets louder as you increase stereo volume. Try putting on talk radio or slow classical - the dead air parts will allow you to hear the whine clearly.

2) pull the fuse on the stereo to remove power to see if it goes away.

3) play the radio with the engine at low idle, and then off - the whine should disappear.

ZoinksM3 · 09-11-2008, 07:29 PM

Tried with the isolator. No whine. Tried without the isolator. No whine.

The issue is transient for me.

cclboss · 09-11-2008, 08:00 PM

Quote:

Originally Posted by Bronx Cheer

If you think it is an alternator (ground loop) whine coming from the stereo, there are three ways you might be able to check.

1) see if the sound gets louder as you increase stereo volume. Try putting on talk radio or slow classical - the dead air parts will allow you to hear the whine clearly.

2) pull the fuse on the stereo to remove power to see if it goes away.

3) play the radio with the engine at low idle, and then off - the whine should disappear.

Method 3 above doesn't work since the dealer claims the whine is from the engine and not a ground loop. I think the best way is to use method 2, but I am not sure if there is a fuse that controls just the stereo system. Hate to mess around with the electronics of BMW.

If I could just get rid of this annoyance, then the car would be PERFECT!

MDCTFTW · 01-03-2010, 06:49 PM

I just started hearing this too. Any solution?

gundamz · 01-03-2010, 07:22 PM

Quote:

Originally Posted by cclboss

Method 3 above doesn't work since the dealer claims the whine is from the engine and not a ground loop. I think the best way is to use method 2, but I am not sure if there is a fuse that controls just the stereo system. Hate to mess around with the electronics of BMW.

If I could just get rid of this annoyance, then the car would be PERFECT!

Try turning off the radio when you drive your car next time. The whining sound should become more audible.

- gundamz

JCtx · 01-03-2010, 07:29 PM

Just as a comment, when you open a door or the trunk, iDrive starts loading, as most of you already know. But what I didn't know is that the front speakers (and probably all others, but didn't verify it) make the same high-frequency noise you mention, but at a subtle volume. If you put your ear next to the front-door tweeter, it's pretty obvious, but you shouldn't be able to hear it while seated and driving. Try listening to that to see if yours is louder than ours. Or if it's the same noise with the engine off and just gets louder while underway. That might help you diagnose what it is.

My guess is the Nav/iDrive interface, since it uses the stereo speakers for feedback. Good luck, and keep us posted.

MDCTFTW · 01-03-2010, 08:31 PM

Ya I haven't debugged my issue too much. There are a lot of combos that I need to go through to determine what is actually wrong. USB, radio, stereo on/off, car on/off, accelerating, low/high speed, volume up/down ...

quality_sound · 01-04-2010, 03:00 AM

Guys, by definition just having more than one ground point in a car creates a ground loop. It's NOT a ground loop. First we need to get some data points.
How many with this problem have navi?
Does the noise change volume with RPM?
Does it make the noise with the radio fuse pulled?

Off the top of mty head, my guess is it's the HDD spinning up or the alternator. Not an electrical noise, but a physical one. Some Chevys have noisy alternators and their physical noise can be heard through the firewall. Might be the case here.

littleyellowm3 · 01-04-2010, 02:38 PM

Quote:

Originally Posted by cclboss

Hi,

Been driving my M3 E90 for a couple weeks now but I noticed that there appears to be a very subtle high pitch noise that I swear is a ground loop feedback from the audio system. I have brought it back to the dealer and they claim they can't hear it. I understand the M3 engine/exhaust has a higher pitch sound than normal cars but I believe this is coming from the speakers. In normal cars, you can turn off the radio and verify but with the M3, you can only "mute" the audio and the high pitch sound still comes through.

Does anyone else have this problem? Is there an easy way to totally switch off the audio system so I can verify for myself (and the dealer) that there really is a problem? This is very annoying especially on the highway and the car is cruising and there is this high pitch "buzz".

Thanks.

I have the exact same problem. I was able to identify that it is coming from the door tweeters by the mirrors. Just open your door and put your ear up to it. It has been driving me crazy. It is always there. Even if the engine is off. Now that I found where it is coming from, Im taking it to the dealer soon. It has to go away. I cant drive without the windows cracked or the radio up now.

quality_sound · 01-04-2010, 02:50 PM

Do you have iDrive?

JCtx · 01-04-2010, 05:14 PM

Quote:

Originally Posted by Philritter21

I was able to identify that it is coming from the door tweeters by the mirrors. Just open your door and put your ear up to it. It has been driving me crazy. It is always there. Even if the engine is off.

That's exactly what I posted. ALL cars are going to have that (the 3 other M3s I heard had it as well). And yes, it's an iDrive 'feature'

. The only problematic issue is the volume. On my car, you can hardly hear it, so I don't have a problem living with it. I posted this a while ago just to make sure something wasn't wrong with my car. Turns out it wasn't. But if it's too loud on your car, then something might be wrong. Hear another M3 first so you know how to proceed.

And no, it's not there all the time with engine off; it goes away about 5 minutes after you turn the engine off, whether you close the doors or not. If you close the doors, it'd come back (along with iDrive loading noises) when you open a door (or trunk) again. That's why I leave my doors closed only to the first 'click' (not fully closed) when I'm going to work on the car, to avoid draining the battery with electronic crap running all the time. Take care.

quality_sound · 01-05-2010, 01:04 AM

It's an artifact of the HDD running and I haven't been able to find a way around it in any other car with that problem like my old GTI. It sucks.

JCtx · 01-05-2010, 01:21 PM

Quote:

Originally Posted by quality_sound

It's an artifact of the HDD running and I haven't been able to find a way around it in any other car with that problem like my old GTI. It sucks.

It's not the HDD since my car doesn't have one. It has to be the iDrive interface with the stereo system.

The first order of business for OP is to check if his car is louder than others. If yes, it'd be interesting to find out why, but that's be BMW's problem. Good luck.

quality_sound · 01-05-2010, 02:50 PM

Quote:

Originally Posted by elp_jc

It's not the HDD since my car doesn't have one. It has to be the iDrive interface with the stereo system.

The first order of business for OP is to check if his car is louder than others. If yes, it'd be interesting to find out why, but that's be BMW's problem. Good luck.

Then it's the iDrive powering up when you unlock the car. This also explains why it stops after 10 minutes when you lock the car.

SCtud · 02-04-2010, 01:19 AM

wow. finally found a thread on this as i posted a similar topic on e90post.
http://www.e90post.com/forums/showth...47#post6642547

my car just started having this problem (hiss and high pitch frequency from the tweeters). it is coming from both sets of tweeters (ones on the front doors as well as the rear seat tweeters). this was NOT in my car before i had the alarm installed, so whatever they did to my car, it introduced the problem. the alarm install involves adding a horn next to the rear left tirewell, and updating the software so the car recognizes the alarm. they tried removing the alarm, and the high pitch noise was still there.

only one person at the dealer could hear it (apparently all of them have horrible hearing from working in a car shop all day). at the end of the day, they called the problem "normal". this is a complete load of crock since if it was normal, i would have had it before and heard it when i drove my car for the past seven months considering the noise gives me a headache every time i drive my car. also, i have not heard it in any other car (335 loaner, 528 loaner, 328 loaner, etc.). if it is the idrive still running when the car is off, i don't understand why the idrive would send a signal to the amplifier to tell it to emit a high pitch sound plus static? and why would it keep sending the same signal when the car is running?

as a test to the SA, i downloaded the dog whistle app to my phone and asked if he could hear when it was playing a 16khz frequency (similar to the sound being emitted). he could not. nor a 15khz, nor a 14khz. only a 13khz sound he could hear. of course they think it's normal because they don't hear a damn thing. someone please figure this out - i am bringing my car to a different dealer next week to see if they have a more competent staff.

Ca$hOnly · 02-04-2010, 01:29 AM

I've had the same thing since day one. Super high pitched "beeeeeeep" sound. I thought it might be the idrive DVD spinning, but I'm not sure. I've tried to get used to it, but it sure is annoying.

chris719 · 02-04-2010, 01:33 AM

If it's really 16 KHz it's unlikely to be a ground loop. If anyone has access to an oscilloscope they could take a look at it and try to see what the signal is exactly.

It would be detrimental to sound quality but you could probably add a low-pass filter in front of the tweeter if it was high enough.

SCtud · 02-04-2010, 01:35 AM

the dvd spinning is a completely different sound (and very annoying as well, but something i can deal with since it's not constant nor as loud nor as high pitched).

put your ear up to the tweeter when the car is off (right after you unlock your door, or just after your turn your car off). you should be able to hear it quite clearly. this is a bit bothersome that there are several people with this same issue.

09-11-2008, 01:42 AM	#1
cclboss Enlisted Member 4 Rep 31 Posts Drives: BMW M3 E90 Alpine White Join Date: Jun 2008 Location: Hong Kong iTrader: (0)	High pitch sound possible ground loop issue? Hi, Been driving my M3 E90 for a couple weeks now but I noticed that there appears to be a very subtle high pitch noise that I swear is a ground loop feedback from the audio system. I have brought it back to the dealer and they claim they can't hear it. I understand the M3 engine/exhaust has a higher pitch sound than normal cars but I believe this is coming from the speakers. In normal cars, you can turn off the radio and verify but with the M3, you can only "mute" the audio and the high pitch sound still comes through. Does anyone else have this problem? Is there an easy way to totally switch off the audio system so I can verify for myself (and the dealer) that there really is a problem? This is very annoying especially on the highway and the car is cruising and there is this high pitch "buzz". Thanks.
	Appreciate 0 Tweet Quote

09-11-2008, 03:25 AM	#2
nitramsen Private First Class 5 Rep 131 Posts Drives: Many Join Date: Jan 2008 Location: Home Land iTrader: (0)	Hi, I have the same noise in my E90 but I cannot really determine were the pitch is coming from. Maybe ground loop maybe engine. Let me known if you figure out were this is coming from as it is really annoying as you say on highway drives. __________________ The idiot always knows he is right while the intelligent is afraid that he could be wrong.
	Appreciate 0 Quote

09-11-2008, 05:39 AM	#3
southlight Moderator / European Editor 1545 Rep 6,754 Posts Drives: X3M Join Date: Apr 2006 Location: Germany iTrader: (0)	In case you mean a noise coming out of the speakers and only during acceleration I'm interested in the outcome either. Best regards, south __________________ Those forums...WHY NOT? JOIN THE 6MT CLUB GROUP
	Appreciate 0 Quote

09-11-2008, 07:05 AM	#4
ZoinksM3 Private First Class 9 Rep 114 Posts Drives: E90 DCT M3 Join Date: Aug 2008 Location: Irving, Tx iTrader: (0)	Ditto, very fain't whine. I called that the turbo in my first car. I use an iPOD almost exclusively so I'm wondering if the USB port isn't grounded properly. This was a known issue in my old Lexus which they said they wouldn't fix. I ended up buying a stereo mini-jack ground loop isolator which fixed it. PAC SNI-1 for anybody interested. I'll try it out and report back. I don't think I'll accept the same story from BMW as from Lexus. Lexus just had a 12v port and a line-in jack. I spent $400 for the iPOD option. __________________
	Appreciate 0 Quote

09-11-2008, 11:08 AM	#5
Bronx Cheer Private 11 Rep 66 Posts Drives: 2009 M3 sedan Join Date: Aug 2008 Location: DC iTrader: (1)	If you think it is an alternator (ground loop) whine coming from the stereo, there are three ways you might be able to check. 1) see if the sound gets louder as you increase stereo volume. Try putting on talk radio or slow classical - the dead air parts will allow you to hear the whine clearly. 2) pull the fuse on the stereo to remove power to see if it goes away. 3) play the radio with the engine at low idle, and then off - the whine should disappear.
	Appreciate 1 CurbBender'9071.50 Quote

09-11-2008, 07:29 PM	#6
ZoinksM3 Private First Class 9 Rep 114 Posts Drives: E90 DCT M3 Join Date: Aug 2008 Location: Irving, Tx iTrader: (0)	Tried with the isolator. No whine. Tried without the isolator. No whine. The issue is transient for me. __________________
	Appreciate 0 Quote

01-03-2010, 06:49 PM	#8
MDCTFTW Lieutenant Colonel 123 Rep 1,973 Posts Drives: E92 DCT Join Date: Apr 2008 Location: Norcal iTrader: (0)	I just started hearing this too. Any solution? __________________ MDCT ... so you can drive and eat a hamburger at the same time.
	Appreciate 0 Quote

01-03-2010, 07:29 PM	#10
JCtx Major General 258 Rep 5,012 Posts Drives: No BMW yet Join Date: May 2008 Location: El Paso TX iTrader: (0)	Just as a comment, when you open a door or the trunk, iDrive starts loading, as most of you already know. But what I didn't know is that the front speakers (and probably all others, but didn't verify it) make the same high-frequency noise you mention, but at a subtle volume. If you put your ear next to the front-door tweeter, it's pretty obvious, but you shouldn't be able to hear it while seated and driving. Try listening to that to see if yours is louder than ours. Or if it's the same noise with the engine off and just gets louder while underway. That might help you diagnose what it is. My guess is the Nav/iDrive interface, since it uses the stereo speakers for feedback. Good luck, and keep us posted.
	Appreciate 0 Quote

01-03-2010, 08:31 PM	#11
MDCTFTW Lieutenant Colonel 123 Rep 1,973 Posts Drives: E92 DCT Join Date: Apr 2008 Location: Norcal iTrader: (0)	Ya I haven't debugged my issue too much. There are a lot of combos that I need to go through to determine what is actually wrong. USB, radio, stereo on/off, car on/off, accelerating, low/high speed, volume up/down ... __________________ MDCT ... so you can drive and eat a hamburger at the same time.
	Appreciate 0 Quote

01-04-2010, 03:00 AM	#12
quality_sound 8 tracks of madness 62 Rep 2,735 Posts Drives: Slowly Join Date: Jun 2009 Location: At home iTrader: (1)	Guys, by definition just having more than one ground point in a car creates a ground loop. It's NOT a ground loop. First we need to get some data points. How many with this problem have navi? Does the noise change volume with RPM? Does it make the noise with the radio fuse pulled? Off the top of mty head, my guess is it's the HDD spinning up or the alternator. Not an electrical noise, but a physical one. Some Chevys have noisy alternators and their physical noise can be heard through the firewall. Might be the case here.
	Appreciate 0 Quote

01-04-2010, 02:50 PM	#14
quality_sound 8 tracks of madness 62 Rep 2,735 Posts Drives: Slowly Join Date: Jun 2009 Location: At home iTrader: (1)	Do you have iDrive?
	Appreciate 0 Quote

01-05-2010, 01:04 AM	#16
quality_sound 8 tracks of madness 62 Rep 2,735 Posts Drives: Slowly Join Date: Jun 2009 Location: At home iTrader: (1)	It's an artifact of the HDD running and I haven't been able to find a way around it in any other car with that problem like my old GTI. It sucks.
	Appreciate 0 Quote

02-04-2010, 01:19 AM	#19
SCtud First Lieutenant 20 Rep 329 Posts Drives: 2008 E93 M3 Join Date: May 2009 Location: CT iTrader: (1)	wow. finally found a thread on this as i posted a similar topic on e90post. http://www.e90post.com/forums/showth...47#post6642547 my car just started having this problem (hiss and high pitch frequency from the tweeters). it is coming from both sets of tweeters (ones on the front doors as well as the rear seat tweeters). this was NOT in my car before i had the alarm installed, so whatever they did to my car, it introduced the problem. the alarm install involves adding a horn next to the rear left tirewell, and updating the software so the car recognizes the alarm. they tried removing the alarm, and the high pitch noise was still there. only one person at the dealer could hear it (apparently all of them have horrible hearing from working in a car shop all day). at the end of the day, they called the problem "normal". this is a complete load of crock since if it was normal, i would have had it before and heard it when i drove my car for the past seven months considering the noise gives me a headache every time i drive my car. also, i have not heard it in any other car (335 loaner, 528 loaner, 328 loaner, etc.). if it is the idrive still running when the car is off, i don't understand why the idrive would send a signal to the amplifier to tell it to emit a high pitch sound plus static? and why would it keep sending the same signal when the car is running? as a test to the SA, i downloaded the dog whistle app to my phone and asked if he could hear when it was playing a 16khz frequency (similar to the sound being emitted). he could not. nor a 15khz, nor a 14khz. only a 13khz sound he could hear. of course they think it's normal because they don't hear a damn thing. someone please figure this out - i am bringing my car to a different dealer next week to see if they have a more competent staff.
	Appreciate 0 Quote

02-04-2010, 01:29 AM	#20
Ca$hOnly Major 47 Rep 1,073 Posts Drives: E92 M3 Join Date: Apr 2009 Location: In ur fridge, eatin ur foodz iTrader: (5)	I've had the same thing since day one. Super high pitched "beeeeeeep" sound. I thought it might be the idrive DVD spinning, but I'm not sure. I've tried to get used to it, but it sure is annoying. __________________
	Appreciate 0 Quote

02-04-2010, 01:33 AM	#21
chris719 Major General 7334 Rep 7,299 Posts Drives: '08 M Roadster Join Date: Oct 2007 Location: NJ iTrader: (0)	If it's really 16 KHz it's unlikely to be a ground loop. If anyone has access to an oscilloscope they could take a look at it and try to see what the signal is exactly. It would be detrimental to sound quality but you could probably add a low-pass filter in front of the tweeter if it was high enough.
	Appreciate 0 Quote

02-04-2010, 01:35 AM	#22
SCtud First Lieutenant 20 Rep 329 Posts Drives: 2008 E93 M3 Join Date: May 2009 Location: CT iTrader: (1)	the dvd spinning is a completely different sound (and very annoying as well, but something i can deal with since it's not constant nor as loud nor as high pitched). put your ear up to the tweeter when the car is off (right after you unlock your door, or just after your turn your car off). you should be able to hear it quite clearly. this is a bit bothersome that there are several people with this same issue.
	Appreciate 0 Quote