This has just started in the past few days. About 90 seconds after I turn off the engine, it will start emitting what sounds like an almost perfect sine wave at a little over 1kHz. It lasts for another 90 seconds or so, and then quickly fades out.

Audio here: https://db.tt/KKJ4IFls

Because it doesn't last long, I haven't yet been able to pinpoint exactly where it's coming from, but it seems to be from the engine compartment.

As you can hear in the audio, it continued even when I took the key fully out.

  • If you quickly start the car back up while the noise is going on, does it stop? Then, if you shut it off again, does the noise come right back? What year/engine on your RAV4? Aug 6, 2016 at 11:35
  • Does it only happen when you've been running your A/C?
    – Jason C
    Aug 6, 2016 at 19:27
  • It's a 2013. I'll check which engine. Going to have to wait until it does it again, but the A/C is on every time I drive (it's about 90°F out there).
    – Isvara
    Aug 6, 2016 at 22:40
  • Looking at the posted answer, it does sound kind of electronicy doesn't it. Does that noise happen to be the same pitch as the little alarm that sounds when you e.g. open your door with the car off but the keys in the ignition, or leave your headlights on or whatever?
    – Jason C
    Aug 12, 2016 at 0:11
  • I mean, it's pretty much a perfect sine wave, unvarying, at about 1020 Hz. That's a super weird sound to be something mechanical. Even air or fluid whistling through a pump under pressure you'd still expect to have some side frequencies or at least a varying pitch, and not just be a pure sine wave.
    – Jason C
    Aug 12, 2016 at 0:22

1 Answer 1


That sounds like a speaker type sound.. Is there an old alarm siren fitted somewhere that could be causing this? If so try unplugging it.

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