The sound of a bad penny - Finding counterfeit coins by sound

Acoustic method could quickly catch counterfeit coins.

You might assume that counterfeiters only bother with high-value bank notes, but there is a chance that some of the coins jangling around in your pocket right now are fake. If Mototsugu Suzuki gets his way, it may be that jangling that gives them away.

Suzuki, a researcher at the Tokyo Metropolitan Police Department's Criminal Investigation Laboratory in Japan, has developed a way of examining coins based on the sound they make.

In Suzuki's method, coins slide down a slope and then fall onto a brass block. The sound they make on impact is relayed via a microphone to a computer.

Although the human ear cannot usually tell the difference between real and fake, a computer can. Genuine 500-yen coins showed four distinctive peaks of natural resonance frequencies in the 5-20 kilohertz range. This was not the case for fakes; some fakes produced only three peaks, while others showed four but at different frequencies to genuine coins.

In addition to helping detect counterfeits, the sound data could be used to build up a database of fake coins, suggests Suzuki. This might help law enforcement officers to prove how many coins one counterfeit operation is responsible for.

This would make for an awesome Instructable! Start with these two Instructables and get dropping pennies!

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I found this site a few days ago:

It tracks the intrinsic, or "melt", value of coins based on current metals prices. That is to say the "melt" value is the cost, per coin, to buy the metals that go into making that coin. This number changes a little bit every day, depending on the metals market, and the strength of the Former U.S. dollar.

If trends continue, the old American 1/100 and 5/100 pieces (pennies and nickels) may be discontinued in the future, or reissued using some less expensive material, perhaps aluminum or plastic.
See also:

Coin validation apparatus
United States Patent 5062518
Publication Date: 11/05/1991

Coin validation apparatus having a coin chute including a hard striking surface upon which a coin entering the apparatus is directed. A microphone is positioned to detect acoustic vibrations of the coin after it strikes the striking surface. An output from the microphone is applied to a fast fourier transform device to produce a signal analysis of the coin vibration. A weighbridge measuring apparatus which is made up of a flexible strip of resilient material carried on a support at each end is provided. The coin rolls across the flexible strip to cause a temporary deflection of a center portion of the strip. A strain gauge located at the strip center to produce an electrical signal representative of the deflection. A classifier compares the signal analysis and the strain gauge signal with stored data representative of a set of standard coins, for classifying the coin as a particular coin value.

lea.the.pro8 years ago
could you imagine, that before while opening a bag of chips, a cool quarter pound coin came from it and fell on the ground as i popped it open? i was 4 years old then and internet is nonexistent. the weird thing is how would such a coin be inside a bag of chips that was manufactured in the philippines.

btw, here is a good site to know about which coins are real and which are counterfeit as well as about coin grading and the likes: Silver Coins
Brennn109 years ago
As a very avid coin collector, I keep a close watch out for these. Very often, coins that are counterfeit show up on eBay, labeled as real. Although, most are named "Replicas" I can tell the difference between older wheat cents, with the recent Lincoln Cents, due to the different metals used in minting the coins. Counterfeiting coins is a REALLY big industry, especially in China, where they counterfeit American coins and currency. Lets just hope when I go to buy a 1916-D Mercury Dime, or a 1909-S VDB Wheat Cent, I won't be cheated out of the large amounts of money those coins sell for.
Yeah, I hate how China is always making the fake ones, putting them on eBay, then ripping you off. It hasn't happened to me, that's why I don't use eBay for coins and stuff. I don't like how they make those proof 1909-S VDB's, and they say replica on the back. They make me mad.
I am a member of a coin forum, and it is amazing how many people find fake coins on eBay. They post links to alert people not to purchase them. In some cases, people bid ridiculous prices to keep "newbies" from buying them. Then they report the seller and the coin.
Let's put it this way.


And my little cousin was holding a penny... I took it from her.. guess what?

It was a 1909-S VDB, About Uncirculated condition.

Just kidding. It was a 1946.. I think.
You scared me for a second there!
mydad has one of those in mint condishion.
No Way!!! That is absolutely awesome!! I know some OK ones going for over $1,000! I wonder how much he payed for it!
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