The easy way to discover the source of the noise is to use a portable radio with a telescoping antenna. Ideally, the portable, handheld radio will have the 49 meter band on it. If not, a nearby band in which you have heard the noise will work.
Go outside. Extend the antenna out. Tilt the radio so that the antenna is horzontal, pointing out and away from your body. While remaining in one spot. spin around slowly making a complete circle. As you turn, the volume of the noise should go up and down. Keep turning until the noise is is at its most quiet and stop turning. At this point, you should be facing the source. However, although you may find yourself starring at a telephone pole, the source may be a medical building, with an MRI machine, behind it. Advance into the direction of the quiet spot (null). Stop occaisionally and do the spin move.