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

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!


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.

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

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.

No Way!!! That is absolutely awesome!! I know some OK ones going for over $1,000! I wonder how much he payed for it!

Isn't it more worth collecting the $1,000 instead of 1c. ? =)

If you are a coin collector you would understand. We have a mindset like no other. We are willing to drop loads of cash on a single coin.

We have a mindset like no other

I think I've just realised that. =)

The $1,000 continually goes down in value, while the other increases :-)

Ahh, but then if you bank it for a few years it reproduces!

Yep, at about 5% interest, while the economy and taxes eat away at it's value at about 3 times that rate. ;-) It is really a lose lose situation

my dad got it a long time ago when he collected coins. he payed 20$ for it.

Damn, he sure is lucky. Now...if I could only go back in time to buy an ounce of gold. Boy, has the price of Gold shot up. Hopefully Silver does the same. Doubtful it will be as high though.

"back in time" lol p.s. please do not swear.

Yeah, you must have been jealous. Dsman1's dad sure is lucky...

I miss copper coins!

Me too. Those were the good old times.. and bad.. but good... COPPER. CRACK. IS. WACK. YU-GI-OH!!!!!!!!!!! Haha just kidding. :P

I have no clue why I still talk to you. (just kidding- well, as far as you know -lol)

I absolutely can not get accustomed to the "new" sound of the penny. The old copper ones sounded like coins, and the new zinc ones sound fake. *shrug*

Amen to that. Bring back the copper! Too bad we only have copper plating on our cents. 1982 was the last year of 95% copper. Those were the days...oh wait, I wasn't born yet.

The other day I accidentally kicked a penny on the sidewalk, and it went clickity click for a few feet. The cheap sound of it made me mad and I gave it a real kicking (my wife, bless her tightness, went running after it ) .

:-) in 1982 I was passing 24 years of age, so I remember the "ping" (dropping them on macadam) well

My wife worked in a bank long enough that she could tell what coin hit the floor by the sound (penny, nickel, dime, quarter...). I read somewhere that you could tell an ancient silver coin from a new copy by the sound, probably due to age hardening.

Well, the different metals used in today's alloys definataly have a different "clunk" to them, compared to the ring of copper / brass coins of old. The copper sandwiched quarters even had a "ring" to them, not having much silver in them. I remember being able to "flip" a quarter and really make it sound off.

this sounds cool.

I once found a silver quarter (US) in a handfull of mixed change because it sounded different than the others.