Found a neat way to measure relief with a ping test and spectrograph

[coinnoob7]

We all know the ping test, whether with a device or balancing a coin on your finger. 90% silver peace/morgan have a fundamental frequency around 4.5khz. Whats interesting is that there are actually two frequencies about 100hz apart because the coin is not a perfect disk, the design breaks the symmetry. The taller the design, the wider the gap between the two frequencies. So by pinging coins and noting the two fundamental frequencies you can infer the relative height of the relief. The app I use on windows cost a few dollars and is called Friture. On iPhone there is an app called Godofoss, but its nicer on windows because you can click anywhere on the spectrograph and read the frequency.

http://friture.org

I find its useful to use the spacebar to pause it between pinging and in the settings turn the time range up to a few minutes and the FFT up over 4k.

[morganman]

As an old timer now i haveno clue what your saying or talking of as i am a total tech
dinosaur foe sure. others here will completely get your post, but sorry, as it frustrates me
all to heck, LOL Thanks for posting in japanese or whatever that is saying LOL

Heck, my gal just bought me another phone afternot having to deal with one of the lousy things
for a few months. To smart for me as i despise texting as i never could figure how!!
print to small anyway to read so screw it- I told her take it back!! Frustrated badly and hard headed

[messydesk]

Do coins of different designs have different spectrograms? Are they different enough between designs and similar enough within designs that you could tell the design by the spectrogram, much like Merlin does with birds?

[RogerB]

You can infer relative differences, but not absolute. Now, if you could develop this test so that Vampires need only "ping" a coin to determine its variety -- then you'd really have something or should that be "someping?"

[Geseas]

You can infer relative differences, but not absolute. Now, if you could develop this test so that Vampires need only "ping" a coin to determine its variety -- then you'd really have something or should that be "someping?"

I am downloading the Linux version as we speak. Interesting! Thanks for sharing.

@@coinnoob7 Do you have any graphs you care to share? I am learning those 'first blush' observations can be so insightful.

[RogerB]

Just to add a little -- The "ring test" was one of the standards for a good coin. There are many letters to the mint director where people complain that a coin does not ring and they suspect it is counterfeit. In various responses the mint states that is a good test for cast or base metal fakes, or for coins that have been hollowed and filled (such as gold filled with platinum). In other instances, examination showed the coin (usually small denomination silver) had a planchet flaw, or severe crack, but was genuine. (Mass and proportion of alloy also has to be examined.)

The letters also indicate that the pitch (frequency) of the ring depended on the precise alloy composition, including trace impurities in copper, and the number of passes the ingot took through the rolling mill. Platinum, iridium and osmium traces in California gold did not seem to have any effect on ring tone.

A thought is that hypothetical range of normal spectrum (including fundamentals and overtones) might completely engulf any contribution to the spectrum from relief. That is, for practical use, can a "CC" coin be identified from the same date "P" coin?

[LateDateMorganGuy]

This is interesting, but not sure I see a commercial application for it.

[messydesk]

This is interesting, but not sure I see a commercial application for it.

The story of so much of what we do.

[iwillbenice]

Sonar ping?

[iwillbenice]

Let sey you are a ping head.
All silver I ping and get pinged back I get pinged.

[pup_picker]

i like the idea but i gotta believe that HOW one pings, will vastly affect the outcome. thickness of surface, type of surface etc.

i'll have to look into this a bit more for silver and gold.

[RogerB]

Try it on dolphins, too. They "ping."

[Geseas]

You can infer relative differences, but not absolute. Now, if you could develop this test so that Vampires need only "ping" a coin to determine its variety -- then you'd really have something or should that be "someping?"

I am downloading the Linux version as we speak. Interesting! Thanks for sharing.

@@coinnoob7 Do you have any graphs you care to share? I am learning those 'first blush' observations can be insightful.

I haven't been able to download, yet. I will keep working on it; there are similar programs available also. I just have to find something that the Chromebook version of Linux likes.

My interest is in detecting the hidden lamination/delamination of a planchet for some crazy reason. I thought someping'en may be a detection tool. A flap of silver must make a different noise, right?

[RogerB]

"A flap of silver must make a different noise, right?"

Compared to.....?

[messydesk]

... A flap of silver must make a different noise, right?

From a coin without a lamination? Yes, but you have to be able to repeatably acquire a ping from the two coins enough times that you know the difference between them is outside the margin of error. If you can get the same spectrogram 10 times with a normal coin, try with an otherwise identical coin with a cracked planchet and see if there's a difference. If not, there's realistically no reason to continue the experiment.

[Geseas]

Thank you John and RWB.

...Yes, compared to a coin without a lamination error. I am thinking a lot of a lamination error is hidden; kind of like an iceberg.

[UNCLE BINGO]

well > Having Pinged thousands of samples of a different kind of Metal in my life , just to listen to if it had cracks , you might be on to something .... definitely worth tying in your identification of anomaly. To be somewhat more convincing in reporting your findings you might need another sample, same mint. same year , same die pair, for a control ,However that might not be possible to get exact . Guess you never know till you try , good luck !

[messydesk]

Thank you John and RWB.

...Yes, compared to a coin without a lamination error. I am thinking a lot of a lamination error is hidden; kind of like an iceberg.

Often this is the case, but it's hard to tell. I find the prospect of conducting these sorts of experiments interesting, but I'm not up for doing it myself at this time. Lots of things to test:

Baseline tests:
- Consistent spectrogram for a single coin
- Consistent between different coins of same type and composition
- Noticeable difference between coins of same type but different composition (bronze vs. Zincoln cent, 90% vs 40% vs clad). We can hear these differences fairly easily.

Interesting tests:
- Noticeable difference between coins of different structural integrity (normal, cracked planchet, large lamination).
- Difference between coins of different size but same composition (90% 10c, 25c, 50c, $1). Is spectrogram simply shifted up for smaller coins?
- Difference between MS and lowball coins (both different relief and different mass).
- Difference between struck and unstruck planchet (different relief, different mass).

Done correctly, the results could be pretty interesting. You'd also end up showing how to construct a device that give a consistent ping such that someone else could repeat your tests or use your results to determine what type of coin they have.

[Geseas]

well > Having Pinged thousands of samples of a different kind of Metal in my life , just to listen to if it had cracks , you might be on to something .... definitely worth tying in your identification of anomaly. To be somewhat more convincing in reporting your findings you might need another sample, same mint. same year , same die pair, for a control ,However that might not be possible to get exact . Guess you never know till you try , good luck !

Thank you Bob for the Luck and food for thought.

I am not familiar at all with this metal pinging spectrograph technology. It 'sounds' like you may have some experience although with different metals.

Was there some consistency within a sample?

In John's words, would you expect to get a "- Consistent spectrogram for a single coin?"

An 'easy' repeatability with not to fancy equipment.

[UNCLE BINGO]

Hi G ... What @messydesk is talking about is much more scientific and broader spectrum than what I have suggested to you . We ping cast iron all the time because it rings and resonates just like bell . if the sample is intact there is a most definable ring to it . If there is any kind of crack this familiar sound does not resonate , Probably because the sound waves are not in sink at the flaw and instead cancel each other out . lay mans explanation there but it works . not going to get into any 40 year old physics theories (For me anyway ) about sound waves , but this spectrograph thing gives you a readout ... All I was saying to you is if you think your one anomaly in your 1878 Morgan could possibly be a crack or lamination error , I bet you could prove it to your self one way or another by having two duplicate samples and compare the read out. The tinkling of silver LOL Good luck