alternator noise in bluetooth?

[garudatwo]

Hi folks,

Has anyone had an issue with alternator noise when using bluetooth? Here's my scenario:
USB audio/FM: no issues
Bluetooth: no issues when in accessory mode, very on/off high pitch sound when in EV mode, consistent high pitch sound when engine is on, which varies a bit with speed.

 

[Space Truckin]

I am using a Samsung Galaxy S8+, have not run into this issue though...JM2C...I could be wrong...:tongue:

 

[garudatwo]

Thanks, I should note I don't even need to connect anything for it to make that sound, e.g. this happens when source is switch to bluetooth even when disconnected from my phone.

 

[Space Truckin]

Hmmm....

 

[L.L.]

I haven't heard the alternator noise either. Will try to pay more attention the next time and see if it is present in the various drive modes.

Do you recall if it was during the day (headlights off) or at night (headlights on) or does it not matter?

 

[garudatwo]

No difference for me, both headlight on/off. Seemed like one of the systems is causing this interference, but I can't quite figure out. Off to the dealer tomorrow...

 

[L.L.]

Ran the car in EV mode for a little while tonight with the phone paired via BT and with audio input switched to BT. Can't say I heard alternator whine through any of my speakers... just the standard EV motor noise (could that be it?). Please let us know what the dealers finds.

 

[Old Guy]

I am not a 2nd generation owner; but, are you sure that the NSX has an alternator. That would be a little strange because most hybrids use a DC-DC inverter to convert the high voltage from the hybrid drive battery to power up the vehicles 12 v electrics and charge the 12 v auxiliary battery (assuming the car has one). That DC-DC inverter can generate electro magnetic interference (EMI) because it is switching the DC drive battery voltage, probably 400 - 1000 times a second to do the voltage conversion. The motor / generators in the hybrid drive system are variable speed motors and the inverters that facilitate the motor speed control also switch the DC at high frequencies that are variable based upon the motor speed. As such, the hybrid drive systems also have great potential to generate EMI.

The Bluetooth radio system operates in the unlicensed 2.4 Ghz range (thousand x thousand x thousand hertz!). I speculate that it is unlikely that the NSX's drive electronics are interfering directly at the Bluetooth radio level. If you were operating a microwave oven in your car - that would definitely mess up your Bluetooth radio big time. However, the NSX motor / generator drive electronics probably generate some fairly hefty currents in the low kilohertz range. It is entirely possible that these big currents are coupling electromagnetically directly into whatever Bluetooth device you have binding to the cars system and generating interference right inside that device. In that case it becomes a question of how immune your particular Bluetooth device is to the EMI that the car is generating which might explain why others do not report interference. Magnetically coupled interference can be altered by placement. Perhaps move your device around to see if that alters the amount of interference that occurs.

Your Bluetooth device may have been tested to make sure that the interference it generates complies with the applicable standards. It may not have been tested to insure that it is immune to the EMI generated by a hybrid drive, in part because there may not yet be any applicable standards for hybrid drives. Also, even if the standards exist, they don't necessarily guarantee that there won't be a problem, particularly if you put the device close enough to the source of the EMI.

 

[Olyar15]

I'm pretty sure you can't induce alternator whine into a bluetooth signal, since it is digital. If the interference is bad enough, it will disrupt the signal, but not cause an audible whine.

And yeah, the NSX doesn't have an alternator.

 

[bngl3rt]

I am not a 2nd generation owner; but, are you sure that the NSX has an alternator. That would be a little strange because most hybrids use a DC-DC inverter to convert the high voltage from the hybrid drive battery to power up the vehicles 12 v electrics and charge the 12 v auxiliary battery (assuming the car has one). That DC-DC inverter can generate electro magnetic interference (EMI) because it is switching the DC drive battery voltage, probably 400 - 1000 times a second to do the voltage conversion. The motor / generators in the hybrid drive system are variable speed motors and the inverters that facilitate the motor speed control also switch the DC at high frequencies that are variable based upon the motor speed. As such, the hybrid drive systems also have great potential to generate EMI.

It certainly does not have an alternator. In fact, there are no belt-driven accessories on the engine whatsoever.

 

[Old Guy]

I'm pretty sure you can't induce alternator whine into a bluetooth signal, since it is digital. If the interference is bad enough, it will disrupt the signal, but not cause an audible whine.

And yeah, the NSX doesn't have an alternator.

You are correct that it won't couple at the RF level; but, if the EMI couples at the device level it could create modulation effects that may be present in the audio signal. Depending on how the device handles the audio data before it ends up as a data packet at the RF level may make it susceptible to interference that shows up in the final audio signal.

 

[garudatwo]

Thanks for the info guys, especially old guy with the deep dive. EMI shielding on the headunit's bluetooth module sounds like a possible culprit, as I'm getting the whine even without any bluetooth devices connected to the unit. It's currently sitting at the dealer, but the tech agreed it's not normal.

 

[craigSt]

We had a similar problem with a rented car in Greece, unfortunately the guy from the renting company couldn't explain what was the reason (but looks like he was aware of the problem). We really enjoyed driving in Greece though, the country is beautiful and has business potential IMO. Saw a couple of really nice villas for sale in Athens, thinking of investing myself this summer.

 

[garudatwo]

Issue that NSX techs are aware of but with a workaround.

There's interference coming from the harness, but running the headunit at 40% max volume but with device volume maxed, I can't hear the whine anymore.