Intermittent tone/hum from inside cabin

[matt88]

After about 50km/30mi of driving, an intermittent hum would sound from somewhere within the cabin. The tone lasted the same duration each time; about 1 second. It was always the same tone, and almost sounded like a horn honking from a distance. I ruled that out, since there were no other cars around. I'd approximate a tone of about 740 Hz, with a triangular waveform (not quite as buzzy as a sawtooth/squarewave, not quite as pure as a sine wave). It wasn't very loud, and was too difficult to identify the source while driving. The tone would only play when I was in motion, between 5 and 35 mph. It would never play while stopped. The tone played randomly, with a period of 1 to 6 seconds between play

I am convinced the tone was electronic:

• I removed all electronics from USB/12V sources
• Turned off my phone
• Turned off the radio
• Turned off the Climate Control
• Rolled windows down/up to see if the noise was external to the vehicle; it was not

After all of these were attempted, the noise persisted. I gave up and pulled over. Turned off the vehicle. Opened/closed the driver door and restarted the vehicle. I then drove in similar conditions for 10 minutes and the noise did not return.


If anyone else has had a similar experience, where you thought a short electronic tone was being played, let me know. I won't be bringing this issue up with the dealer until my next oil change, as I don't consider it urgent. I have 40000km/24850km on the vehicle.

 

[RandyH2]

Could it be the fan for the heated/cooled seats? If I recall correctly, that fan runs intermittently. One fan under each front seat if you have the cooled seats.

 

[RandyH2]

Wow, I just checked 740 Hz- that is higher pitched than I expected. The fans seem to be much lower, maybe 130 Hz? Hmmmm.....

 

[RandyH2]

Cool that one can Google a frequency and get a Youtube video:

 

[RandyH2]

Going for the one that has happened to me- do you have kids? I once found a fast-food toy stuck between rear seats, it didn't do anything when the car was idle but road bumps were enough to make it beep randomly.

 

[matt88]

Going for the one that has happened to me- do you have kids? I once found a fast-food toy stuck between rear seats, it didn't do anything when the car was idle but road bumps were enough to make it beep randomly.

The fact that it was present for about 10 minutes of driving, but not again after a restart makes me think it was connected to the vehicle somehow.

Could it be the fan for the heated/cooled seats? If I recall correctly, that fan runs intermittently. One fan under each front seat if you have the cooled seats.

Maybe this was it. My heated seats were on (sore back). Maybe the engine off, open/close door, engine ON turned them off.