The new way to uncover adulterated goods - Identify liquid by analysis the knocking sound

    Cheating by blending cheap solvents into gasoline and selling it to the public is a phenomenon that is not uncommon all over the world. We are trying to find a simple way for the public to tell the quality of gasoline quick.


It was just a flash through the brain when we came across the brand-new way to differentiate the genuineness of oils.

We hypothesized that knocking at different liquids makes different unique sounds, so we can use this unique sound to  Identify liquid.



After investing a lot of time and ideas, we successfully set up a stable testing devise.

With this devise, we found that different liquids have their unique characteristics. One liquid produces one pattern signal and it is stable. The devise can tell the differences between different liquids indeed.


Can we use this system to identify fake gasoline?


We found that with our method, we could undoubtedly identify a fake gasoline with mixed solvents.



We found that fake wines are a big problem too.

But trying to test liquids in glass bottles is an even bigger challenge.

After redesigning and remanufacturing,



Eurika!  Eurika!  Eurika!  It works.

    We can use this brand new method to tell if the original wine in a bottle had been replaced with adulterated alcohol. We can even tell if a bottle of grape wine had been replaced with another one.

In the future, people around the world can use their microphones and personal computers to do the diagnostic job by themselves.


(left: Monique Hsu , right: Gina Wang)

WE are in junior high school from Taiwan. We are classmates and good friends from kindergarten. Let us to introduce ourselves respectively.

Hi, I am Monique Hsu. For me, science is my specialty and hobby.  I love chemistry, it's about CHANGES, but meanwhile, some rules are NEVER changed,  for me, it's like our society. But it's much more orderly. And in fact, the world we live in is a combination of chemistry, lands and ocean, sky and clouds, houses and cars, even you and me... are all following the chemical rules, isn't that beautiful?

Hello, I am Gina Wang. From my childhood, I'm always curious of biology and astronomy. I often ask my mom many questions such as “the origin of life”, “the birth of the universal”…etc. When I was in the elementary school, I got many opportunities to do independent studies.

I care about all the life around the world, of course, including the human being. If we could get the first place, I would like to research the creature that nobody has ever seen before in the ocean. I'll be very excited to swim with the sea lion or other marine organisms. It's the very best dream of my life. Furthermore, we could improve our research to help more people around the world more conveniently and economically. 




We want to let the public all around the world can use our simple equipment at home by themselves to identify the gasoline and the wine that is might fake.

We focus on 3 goals:

1. Does a certain liquid always have the unique knocking sound?  We also wonder if different liquids have different characteristics of sound.

2. Could we apply the  liquid percussion identifying device to identify the gasoline that is adulterated with other solvent?

3. We wonder if our device can also identify whether the liquor in the bottle is adulterated or not.


    There are many cheap and illegal solvents that are adulterated to gasoline everywhere in China. This situation could  cause cars lose its power or be out order. This problem is pervasive throughout South Asia and has also been reported in Greece, Brazil and African countries.(Interdisciplinary Thoughts Effects of Gasoline Adulteration

    We wonder if we could find a simple identification for liquid, all the people globally will be  pleasantly surprised. 

    “Water” and “OIL” . It will be different the sound of knocking the bottle between water and oil. Therefore, it should be different between different liquids when those liquids are knocked.We want to use this method to identify whether the  gasoline is adulterated another solvents. When everybody to realize the project would like to say “ It sounds reasonable,but it is hard to utilize. However,After our experiment,  We  find that it works .The method is easy and creative, everybody globally could use this way to inspect the adulterated gasoline.

    Meanwhile we also found it as following: In 2011,several Russians were killed after they drank the adulterated alcohol In Turkey. In 2011, 52 persons were  killed due to consumption of liquor with methanol  in Ecuador. In 2014, 30 persons were  killed due to consumption of liquor with methanol  in Czech. The problem of adulterated alcohol is becoming seriously in  China. The adulterated alcohol will  hurt  for all the people globally very much. This problem Disturbs all the people around the  world.



PART A:  Designing and Building a Liquid Percussion Identifying Device

   To construct a stable percussion device, a pendulum is set at a fixed elevation, which allows the pendulum to strike with the same amount of force and at the same location during each free fall. A sound recording system is also set up at a fixed position to record the noises in a stable environment.

Liquid Percussion Identifying Device II

    It is difficult to achieve the exact same striking conditions each time when the pendulum hits a variety of bottles. We have designed a method that allowed the bottles to be placed directly on the tabletop.

Liquid Percussion Identifying Device III


PART B: Recording the fluid percussion sounds and displaying the results in a graph

The percussion sounds are recorded and analyzed by using the "Audacity" freeware. The following graphs show an example of the analysis:


PART C:  A spectrum graph of the audio recording

1.   There are always variances each time a certain type of fluid is struck, therefore we only extracted the frequencies that were common across all samples.

2.   We collected four recording samples from each type of fluid, and then superimposed the four frequency spectrograms with PhotoImpact.

    Four frequency spectrograms  superimpose to one.

3.   Changed the colors with PhotoImpact

 4.   We used PhotoImpact to filter out any signals that were not common in all four samples.

利用PI臨界值   取  四次中疊到三次.jpg

The final frequency spectrogram. We use this frequency spectrogram to represent "the characteristic frequency spectrogram" of this liquid.


PART D:  Comparing the frequency spectrograms of different types of fluids

1. We used two different colors to represent each type of fluid

2. To analyze the frequency spectrograms of the two types of fluids, we superimposed the two characteristic frequency spectrograms with PhotoImpact.

          Green:  Normal Gasoline

          Red:Adulterated Gasoline (10% Methanol Gasoline)





1. Can we use the knocking sounds to identify different liquids?

  1. The same liquid’s audiograms always act the same. Different liquids’ audiogram are obviously different.

  2. So we can know: we can really use the knocking sounds to identify what kind the liquid is.


2. Can It Determine Adulterated Gasoline By the knocking sound? 

(detect by Liquid Percussion Identifying Device II

  1. After adding methanol, the knocking sounds are obviously changed. From frequency spectrogram, we can see that there’s a 30 Hz peak, and the adulterated Gasoline 30 Hz peak is gone.

  2. So we can know: we can really use the differences of their knocking sounds to identify Adulterated Gasoline, which is a really serious problem all around the world.


3.  Can we use the differences of their knocking sounds to discern “the wine in glass” and “the same concentration methanol”?

(detect by Liquid Percussion Identifying Device III

  1. When we use Liquid Percussion Identifying Device III  we find that the signal of frequency more than 50 Hz is stable and reliable. The signal of frequency less than 40 Hz is not very stable. 

  2. In the later experiment that we exchanged the bottles, we discovered that the high frequency(above 1000 Hz) is the sound that the BOTTLE makes, the medium frequency (70~700 Hz) is the signal that just belongs with the LIQUID.

  3. From the significant  signal in the medium frequency, we can obviously identify the real liquor and the methanol solvent.

  4. So we can know we can really use  the differences of their knocking sounds to make sure if the liquor in the bottle was changed into unhealthy solvent BEFORE OPENING THE BOTTLE.


4. Can we use the differences of their knocking sounds to identify the wine in the glass bottle to make sure is the wine the real one or replaced by a different one (but cheaper)?

(detect by Liquid Percussion Identifying Device III

  1. The high frequency(above 1000 Hz) is the sound that the BOTTLE makes, it’s stable.
  2. The medium frequency(70~700 Hz) can help us to easily identify the wine in the glass bottle is replaced or not.
  3. We can really use the the differences of their knocking sounds to find out if the wine in the glass bottle is replaced by another wine or not.


  1. Knocking at container of different liquids makes different sounds. The sound of each liquid is unique and so this can be used for differentiation.

  2. We can definitely identify a gasoline that had been mixed with cheaper solvents with this knocking differentiation analysis method.

  3. Without opening the bottle, we can tell if the liquid in it is of adulterated alcohol, or if the grape wine in it has been replaced by some other kind.


    With this simple method, people around the world can set up their own diagnostic equipment by using a regular microphone and a home personal computer. People can tell if the gasoline they bought the gas station supplied had been blended with other solvents. They can also tell if the wine they bought is as reliable as before, if it is made of adulterated alcohol, or if it is still the genuine high quality red wine rather than a cheap one.

We are trying to make a smaller, more portable and stable testing device.




 Taihang military network (2015)  15 March party exposure Shandong refineries to produce substandard gasoline refueling the car broke down from  

Bibek Baral(2011)Interdisciplinary Thoughts Effects of Gasoline Adulteration from

BBC NEWS(2011)Turkey arrests after adulterated alcohol kills Russians  from

ecuadortimes(2013)Three killed due to consumption of liquor with methanol  from  ecuadortimes 18 May 2013

FT Chinese Network (2013) 2012 Czech Republic due to the adulterated liquor while 30 people were killed and counterfeit problem again sounded the alarm to the British "Financial Times" Allen • Rabe Porter Washington, Jan • Qieensiji Warsaw reports from

IANS Thaindian News(2010)30 wineries making adulterated liquor shut in China from

China's State Administration of Quality Supervision, Inspection and Quarantine (2014) Consumption of alcoholic beverages in the world 30% of counterfeit products from

Thaindian News(2010)30 wineries making adulterated liquor shut in China


Teenmaar News(2014)Adulterated whisky is sold in a wine shops from



This study is interesting but the time spent than expected, and we are grateful to each other for that we can cheer up each other during our experiment period. We want to thank our  natural teachers gave us inspiration, Discuss with us, Help us prepare equipment and accompany us through this hard but interesting times.

I would also like to thank Yuan-Chen Liu and Yao-Ming Yeh two smart and enthusiastic professors.  they gave us a lot of useful advice. It is difficult to see the difference with your eyes between the two graphs.

Professor Yao-Ming Yeh taught us that we can use a computer overlay way to distinguish the two graphs. This proposal helped us greatly. We are  very  grateful!