Humming Noise at Low Vacuum

[FrmRgz2Rchz]

Have you ever blown over the top of a pop bottle? You get that sorta deep hum. Well, I hear this nearly every time my car is at partial throttle and the vacuum is just below 5. It seems to occur more times when the throttle is closing. Inside the car, the noise is coming from the far left side of the engine, almost sounds like the wheel-well. Anybody ever had to deal with this?

[FrmRgz2Rchz]

Am I the only one that has this problem? I'm guessing it's a vacuum leak, but my gauge doesn't show anything abnormal.

[IggDawg]

is this on the NA legacy or one of the turbo legacies? the NA 2.2s get a hum like that when the silencer is removed. my wife even gets it on her 2.2l impreza.

[FrmRgz2Rchz]

It's a turbo. I do have the silencer ('snorkus') removed. Does it only happen at low vacuum on her car? I usually hear it at about 2-5 in. hg If i can throttle it just right, I can make the sound stay there for several seconds. It's more annoying than anything. There aren't any major problems that I can associate with this.

[boostjunkie]

I don't get a hum so much as I can hear the turbo spooling . . . woooooshhhhhhhhhhhhhhhhhhhhhhh . . . *shrug*

[Sir Yach-o]

I get a deep resonance when I throttle just right, too, at about 20% according to the TPS. I've got a different intake on mine, but I'm pretty sure that it's because of the same concept as the bottle thing. If you have the right amount of air flowing in anything, you'll catch the resonant frequency of the enclosure. Bottles and throttles, doesn't matter.

[FrmRgz2Rchz]

Boost leak is the culprit!! I had the leak fixed for a day and it went away. But now it's back.