Airbus A320 Whistling Sound

Last week, aircraft landing at SFO were routinely passing over my house at ~10,000ft. Some of these aeroplanes  made a ghostly whistling noise for 5-10 seconds, and I used Plane Finder app to identify them as the Airbus A320. I don't mind the brief whistle noise. But what's causing it?

A320whine.com has the answer, and Airbus has the solution to eliminate this noise.

 "The noise is caused by air passing over circular vent holes under the wing, similar to the wind blowing over a bottle – just a much larger scale. These annoying wailing sounds good be heard on the ground ... "   -A320whine.com