By James B. Wright

Learning to interpret sound anomalies on your metal detector.


Noise comes to those who would use an electronic metal detector in three different basic forms:
1) Locally generated sounds (such as motors, river rapids, people talking, etc.).

2) Equipment-generated sounds (whistles, squawks, buzzes, etc., from equipment maladjustment or defects).

3) And a third noise, which is the sound of a good piece of equipment operating the way it should.

The counter-measures which must be taken against the first two types of noises should be obvious. Kill the engine, stop the talking or wear headphones which prevent outside noises from entering the ear. And, of course, adjust the equipment properly, or have it fixed, and learn to adjust it properly.

The third type of noise is the good type. It is the noise that is created when a good instrument is set up right and working most-efficiently. This noise is a “frying” sound, kind of like rain on a quiet lake, the wind through the pines, a gentle rapid on the river or a crowd at a ball game. It is a good, clean steady hiss. On a meter, it may be a steady deflection of 25-40% of full-scale.

Unfortunately, you cannot have sensitivity without this type of noise, simply because noise is built into all physical processes and all of nature.

What is “noise” as used in this context? One good example is the sound you get from your television set when it is tuned to an unused UHF channel. This is when you see snow on the TV screen. What you are seeing and hearing is the composite of a large number of random electrical impulses, all continuously being generated by the very atoms which make up the television, as well as those which make up the earth, the atmosphere, the sun and the rest of the cosmos. This is the sound of Nature doing her thing!

So, what’s the point of all this?

When you send a signal into the ground and try to detect a response from bits of gold, or from other types of deeply-buried chunks of metal, you are usually dealing with a very weak return-signal amid a sea of pre-existing natural “noise.” The detector must identify and amplify the desired signal and try to discriminate against the unwanted noise.

This is where the user becomes a part of the detection system. Because human hearing is able to pick out signals buried in noise better than any piece of electronic gear (except for certain radar equipment which is gawdawful expensive).

Why then must we not only tolerate noise but appreciate it? Because, if your equipment is so sensitive that it will sense the intrinsic “noise” of Nature, it will sense an equally-weak signal from your target. If your detector sounds-off on hot rocks or black sands, it is alive and well and doing its job.

Your job is to learn to hear and interpret the anomalies in the noise, the “whisper” that is just slightly different, the smallest change in the pitch of tone.

This is what weeds out the expert from the rest of the pack. He (or she) is like a good sonar-man, picking out the submarine while ignoring the chatter of the whales, the fish and the other noises of the sea.