Monday, June 2, 2014

6/2/14 Report - UPDATED. Metal Detecting in Black Sand, Salt Sand, and Noisy Environments, Gold Rings From Fresh Water Lake, and Increasing Surf

Written by the treasureGuide for the exclusive use of

Gold Ring Found by Robert H.
Photo submitted by Robert H.
On the Treasure Coast the wind has increased and the surf has increased as well.  We'll have to see what that does.  I don't like the angle right now.  I expect the waves to be too much from the East.


UPDATE:  I went to the beach this afternoon after high tide.  I looked at about 8 different spots along a stretch of just over twenty miles.
I didn't see any erosion except for some little six inch cuts at the best of all the spots (not counting Fort Pierce South Jetty Park where the new sand has washed away to create a six plus foot cut already). 

Below are pictures of two beaches that I saw. 

Jensen beach had deteriorated since I last showed it.  Notice the sea weed.  That is a bad indicator.

And also shown below is the best of the natural beaches.  Still nothing but six inch cuts.

Jensen Beach Just After High Tide Today.

The Only Cuts I Found on South Hutchinson Island Other Than At South Jetty Park.

It seems I was right about the angle of the wind and waves.  The waves were a good four to six feet but the angles were wrong and the beach detecting conditions remain poor.


Robert H. detected a fresh water lake close to his home and found three small gold rings and a pendant. 

Above is shown one of the gold rings.  It is a very common type.  If you've been detecting very long you've probably found more than one of these.


The signal you get from your metal detector even if it is a good signal, always occurs in a background of noise.  Noise can keep you from hearing a signal, and therefore cuts down the effective depth that you can detect targets.  Generally speaking, the more noise there is, the more good signals you will miss.

Signal detection theory was developed during World War II when they were developing radar systems and trying to identify blips on a screen indicating the presence of planes.

We all know that you don't have to talk so loud when you are in a quiet room with one other person, and you have to talk much louder to be heard and understood in a noisy room.  That is a simple illustration of the signal in noise problem.

There are a variety of sources of noise when you are detecting.  Some are external, such as wind and the noise of waves breaking.  Some internal, such as tinnitus (that ringing sound you might hear in your ears, and even distracted thoughts.  And some noise come from your detector and the ear phones, such as the signals caused by black sand or minerals, or static in the ear phones caused by various things such as lightening or power lines or nearby metal detectors.

When you do an air test some sources of noise are eliminated or minimized and the noise level can be relatively low.  That results in unnatural results, sometimes better than what you would expect in the field.  In an air test, however, the results can also be worse than what you would get in the field.

Usually there is little difficulty in detecting large shallow targets that create a loud distinct signal, however, when you are trying to detect smaller or deeper targets that give a more faint signal, many of those signals can easily get lost in the noise.

Some detectors give very steady or stable threshold sounds.  That is the sound you hear when the detector is not detecting a target.  Others have a rough or unstable threshold.  An unstable threshold is a source of noise that can cause you to miss perfectly good signals and targets.

If you can adjust your threshold so that it is more steady, you might increase the probability of hearing good signals.  I say "might" because there are other factors that must be taken into account.

If you just increase the volume you will be increasing the loudness of the good signals, but would also be increasing the noise level.  That will not necessarily help you hear the more subtle signals, which can still get lost in the noise.

Here is a key point.  Lowering the threshold level too far to either eliminate the threshold or even to create a very stable threshold is not always a good thing to do.  The threshold level that is best for you will be determined by both your detector and your own operating characteristics.

When you lower the threshold too much, besides eliminating a lot of the noise, you can also lose a lot of the good signals. 

I personally run my detector very sensitive and fairly loud.  I hear the salt mineralization and other noise.   That doesn't bother me much, because I can usually identify those sources and distinguish those sounds from the good signals. 

Since we always operate in a more or less noisy environment, you should be aware that you are always attempting to discriminate between good signals and noise (bad signals.)    Sometimes that is relatively easy and sometimes more difficult.  One good thing to do is make any adjustments you can that will help  reduce the noise to signal ratio, without losing much good information.  That includes changing detector settings, headphone adjustments, and even your mental state.

If you hunt in all-metals or pin-point mode, you will hear a lot of things, many of which are not good targets.  You might, for example, hear concentrations of black sand or salt mineralization.  I'm talking about VLF detectors here.  Some people have a lot of trouble with that.  They think they can't hunt in black sand or salt areas without decreasing sensitivity.  They complain about their detector "falsing."  I don't have much trouble with that.  I generally run my detector the same over black sand as over non-magnetic sand, and over salt mineralized sand as over dry sand.  I hear those effects, but am not bothered by them because I know what they are and can distinguish between those effects and signals produced by targets.   I almost never decrease my sensitivity settings.   I really can't remember having done that.

If you are working over layers of black sand for example, your detector will respond to the black sand.  I say it sounds like a twang.  Smooth undisturbed layers will create a gradual sound, while a footprint or distinct edge in the black sand will sound more like a target.

Watch as you detect these things and you will see what it is that your detector is responding to.

If there is a coin in the black sand you will have a lot of noise but you will still be able to identify good signals.  Coins in black sand will cause signals that are more distinct than the twang of smooth black sand. 

Don't try to avoid all noise.  I've heard very experienced detectorists using very high-end detectors complain that they could not detect in black sand.  I used the same type of detector and detected in black sand every time I saw it and didn't make any adjustments to my settings at all to adjust for the black sand.  I simply listen to the sounds made by the black sand, but can distinguish other sounds created by targets in the black sand too.

The same thing goes for wet salt sand.  Where the salt water has just come up and stopped and then receded, at that edge, you might get a false signal.   Many times you will be able to see the edge that you are detecting. (Anther reason to keep your eyes open while detecting.)

That doesn't bother me.  I know what is creating the signal (noise in this case), and it doesn't bother me at all.  That is part of getting to know your detector.

If you learn to understand your detector and what it is telling you, you won't be bothered by noises like this.  In fact when you understand what it is, the noise becomes information. 

You might be surprised by the types of environments you will be able to detect when you learn how.

Don't try to avoid all noise.  Some noise is actually information when you learn what it is.

Don't be deterred by some falsing.   Try to identify the cause the falsing, which might not be falsing at all.

I'll be watching to see how the beach develops.

Happy hunting,