This story was originally published in Total Electronics Magazine in June 1994. With minor changes, modernizing the text, we put this interesting adventure available for the readers. With a practical circuit we published in our book Bionics for The Evil Genius Panic Circuit that explores the basic idea of the article and it was even quoted in The US TV shows.


It was a big party that left Professor Ventura’s lab, and in front of it was the mayor in person! Bart and Clarke, who had just arrived, thought it was odd, although the field of electronics and the "wonders of electronics and computer science" knowledge of their old master had brought many important people to this lab. As soon as the party had left, Brart and Clarke, who just watched from outside, were called into the laboratory by Professor Ventura himself.

- You are curious to know what happened, aren’t you?

- There’s no doubt about it! - Bart said, as he entered - Are you sure we can know what this is about, or it is a government secret?

The Professor, who rarely Kept secrets from the boys, assured:

- You know I do not keep any secrets from you, and as it is something involving electronics and computers, you can not only know, but you MUST know! More than that: you MUST assist me ...!

Bart and Clarke didn’t say anything! They sat down in the old armchair in the back of the lab to listen to the professor:

- I was actually approached by the mayor. He said he has got a problem and only I can solve it! ...

- Nice! Certainly a problem that can only be solved with the help of electronic ... - interrupted Clarke.

The Professor didn’t seem any cheerful. He paused and continued:

- The problem is neither electronic nor mechatronic, but the solution may be in these sciences. I’ll explain: you know that one of the few problems in Lemon city, our quiet town, is the square downtown. It has always been a very pleasant place to go for a walk in the evening, where young people used for socializing and "flirting" and the elderly enjoyed the small band that played at the bandstand. It was our hang out spot until the birds arrived! ...

Bart was the one who interrupted:

- Yes, the damned swallows which in thousands decided to make the square trees their bedroom!

It was a real problem. After the swallows come to town, besides the huge noise at dusk, when in groups they surrounded the trees to nest, there was the problem of the dirt. The little birds made their needs while flying or on the branches where they settled in a way that became impossible to go near the trees, or even near the square after sunset without being hit!

- The mayor never wanted to cut down the trees ... - continued the Professor - And I agree with him, that’s not the solution! After all, it would be an ecological crime, and the problem and the complaints continued, until he lost his patience last week!

- What happened?

- He was making another inspection to see how much dirt was on the square ground after the swallows nested, which the cleaners of the city were not able to keep clean. Our dear "preboste" got a beautiful "splash" on his shiny bald head! ...

Bart and Clarke laughed, imagining the scene where the mayor would hastily leave the square, wiping his head with a scarf and also remembering the nickname that he had been given!

"Preboste!" In fact, this was the name given to the old military magistrates and featured the high manorial officials, something like a mayor of the "old days”, as the good dictionary said ... The mayor’s posture soon made a mischievous political opponent, who was also a Portuguese Professor, who gave him the title, which soon "was in fashion"! The word was used with double meaning entertaining the people, especially political opponents.

- He should not be "preshitting", ops, “prebosting” without an umbrella! - Commented, humorously, Clarke, not wanting to interrupt Professor Ventura.

- After that, you know: he came to me asking for a "painless" solution to the swallows, or any "electronic device" that prevents them simply to nest in the trees of the square, but without causing any harm the little birds and much less tampering with the ire of the environmentalists! ... the mayor is the type who believes that electronic technology and computer science are the solution to everything! You know! ... So, have you got any ideas?

The problem was clear. The three took their time to think it over.

- How about an electronic scarecrow? A huge mechatronic statue with a microcontroller programmed to shake its arms screaming with a synthesized voice at dusk? It would avoid the approach of the birds! We could make it with the angry face of our dear Preb ... - The idea of ??Clarke was not well accepted for obvious reasons and he was stopped.

- It must be something invisible, which only disturb the birds, without affecting the sight of the square or the presence of people! Knowing how is the tongue of our citizens and the opportunism of the political enemies of our mayor, I'm sure a thousand jokes and nasty comments would arise around such a scarecrow, or anything visible! ...

- Something like a "force field" created by a circuit that avoids the approach of the swallows ... - used to computer games Clarke had some fantasies about energy forms which he didn’t even know if they existed, or how to produce them!

The Professor denied the possibility to take Clarke’s suggestion, but it gave him an idea for a solution:

- I think you gave me an idea to solve the problem! - the Professor said that getting up and going to the blackboard. It was the sign that he had found out something.

Professor Ventura then asked a technical question:

- What can disturb certain small animals and we can not hear?

- Ultrasounds! - The answer was immediate, as they had already worked in electronic scarecrows projects and read enough about in specialized magazines.

- That's right! You know that frequencies above 16 000 or 18 000 Hertz don’t affect us, because we can’t hear them, although there are people who feel strange sensations in its presence, but indeed bother the rodents! Installing powerful ultrasound emitters in silos and food warehouses, you can keep these animals away! ...

But Bart had doubts about the effect in swallows, so he asked:

- But, Professor? Will we have the same result in birds?

The Professor didn’t have many doubts:

- From what I read, some bird species can really be bothered by the presence of ultrasound, and the modulation can help. We apply low frequency audio signals on high frequency signals (inaudible) as a form of frequency modulation or amplitude, and the results obtained have been interesting ... In the United States there are locations with too many birds which have vehicles equipped with powerful speakers. Their purpose is to make noise and scare the birds. I saw it on a documentary.

The Professor continued:

- In the documentary a city square was shown with powerful speakers that emit siren or honking sounds at the time the birds tried to nest in the trees. Even airports have these resources, to scare the birds that are dangerous to aircraft, because they can be drawn through the turbines of the aircraft, causing serious accidents.

But it was the possibility of using "vibrations" produced electronically that animating Clarke:

- Modulated ultrasounds in frequency and amplitude! That is a new fully electronic solution! It wouldn’t bother people as a siren, as it wouldn’t be heard!

- And how to know if this would work here? - Asked Clarke.

- I think in our case, the only way to know if it works is to give it a try, but for this we need to have a plan and talk to the Preboste, i mean the mayor, who must authorize the experiment ...

No need to say that Bart and Clarke helped Professor Ventura on the preparation of the "electronic scarecrow" project.


The idea was simple and relatively cheap: going to the square they found four locations where they could install powerful "tweeters" (acute or high frequency speakers) which would be connected to amplifiers. The amplifiers would receive processed signals from an oscillator controlled by a microcontroller. The oscillator would generate ultrasound signals into a pattern to be studied. Certainly it would not be simple ultrasounds, as Professor Ventura had a theory that they should be combined in a complex way, which would really sensitize the swallows. The tweeters would cover the whole square "filling it up" with modulated ultrasounds which only birds could hear and be bothered, avoiding their approach. It would be like an invisible "ultrasonic force field" able to act only on the birds. With that, they should look for other places to spend the night, attending everybody’s claims:

- With so many forests to nest outside the city, these imps had to stick right to our square!

The system including a microcontroller with a power board, containing oscillators and output stages plus a high-power amplifier, had nothing abnormal for the "experts" in electronics as Bart and Clarke. In fact, they already had this equipment ready in the laboratory, because it was of common use in other applications, of course! After all were in an electronics and computer science technical school!

Professor Ventura spent a whole weekend with the boys developing a program for the microcontroller able to create ultrasound with special features modulation which could have effects on the birds.

Before executing his project, Professor Ventura called Bart and Clarke for a real lesson about the sound and its reproduction.

Asking specific explanations about what would be done in the case of the swallows; Bart and Clarke were promptly attended by Professor Ventura.

- It's just a theory of mine! - He explained while working - I think we should modulate the ultrasound with standards of low frequencies which have something to do with the swallows’ chirping. I’m going to use a microcontroller to control the low frequency oscillators which produce signals that combined with the signals generated by the high frequency oscillators, result in the vibrations we want.

- My theory is that overlapping the ultrasound a modulation which "remembered" the swallows’ chirping, even if they aren’t audible they may have a repulsive effect.

- Way to go!

But it wasn’t only that:

- To have a full control over these sounds, even for reproduction we are going to use a microcontroller.

The microcontroller would be connected to a control shield and another data acquisition shield with a suitable program. It would have several purposes, for example, turn on the circuit just before dusk from the signals of a photo-sensor, when the swallows gather in the square and will be working just over 9 o'clock at night, when it will shut down automatically. Besides, it would adjust the volume and the very sound distribution channels that will be playing on the square.

The first tests with the equipment in the lab were interesting, but as it wasn’t possible to have all the power and a swallow to "tell how it was feeling," there was only one way to know if everything worked: testing on the square in real conditions!

Professor Ventura put it all summarized on paper taking the plan to the mayor who approved immediately, taken over by the fame of the old master’s skills than from understanding something of what he said! Of course looking over a plan so elaborated the enthusiastic mayor couldn’t help himself but making political promises:

- If you get rid of those "pests" I build you a statue on the square!

Professor sniffed and modestly thanked:

- Thank you!

Deep down he wondered how it would be ridiculous to have a statue of whom got rid of a "lot" of swallows which littered the square, full of pigeons that did the exactly same thing.

The building of the "scarecrow" system wasn’t hard, and after with some additional laboratory tests on higher power they found out that actually nothing was heard, although certain unpleasant sensations were noted by Professor Ventura, Clarke and Bart However, they were enthusiastic about the equipment, nobody said anything, thinking it was a natural discomfort due to the heat and the heavy food they had eaten ... A big mistake they would regret later!

The installation on the square brought no major problems, since the city “lent” some employees and ladders which helped position the powerful tweeters on lampposts, properly protected against the sun and rain. There were four points of emission all connected to a control and generation central of ultrasound with a large amplifier of 2000 watts, or Professor Ventura’s Ultrasonic Oscillator, as it came to be called.

- Be very careful with this equipment! - Recommended the Professor, when it was positioned in a place where it should feed from the power grid.

At the end of the day the equipment was ready to be tested. The news about the Professor’s oscillator installation spread and soon everyone in town were eager for the results! However, even on the test day, no one was excited to go to the square. Not wanting to take any risks everybody stayed at home, as ever since the swallows took over the place, avoiding getting “hit” on their heads! No one had plans on getting their clothes or heads dirty!

After Professor Ventura, Bart and Clarke, certainly the mayor was the most anxious person in town. If he could drive out the birds without any damage to provoke the ire of the "eco-boring", as he called them, he could have his political harvest! ...

The day after the installation, everything was ready for a test run!

Only Professor Ventura, Bart and Clarke went to the square near dusk, and then they were prevented with rain coats and umbrellas! The first flocks were beginning to encircle the square making the few people who were on the street find a shelter. As everybody always did, since the swallows became a plague, all the business closed their doors earlier than usual.

- Now! - The Professor said to trigger the device.

Inaudible vibrations in a power that gradually reached 2000 watts, controlled by the microcontroller, invaded the space and their effects began to be felt! Many swallows that were already on the trees of the square took off flight! They looked frightened! The flocks that were still surrounding the square seemed to be increasingly agitated, flying near the ground, however, each turn they were farther from the trees. It was an unusual behavior, but which indicated the system was having some effect!

- It is working! - Bart shouted over the huge noise that the birds were making.

- It’s true! It seems to be working! - The Professor said very proud while on the system control keyboard.

Gradually the flocks of swallows were away and half an hour later, with a little sun light still present, the square was empty! No swallow to get anyone or anything dirty! It was a miracle!

Professor, Bart and Clarke celebrated while a few people who had remained cautious in their houses, after watching the "miracle" came to the square to celebrate! ...

Everyone was happy, "cheers" across the square and even the mayor who had been awaiting news eagerly came to personally greet Professor Ventura.

- It deserves a special tribute to our "savior"! - The mayor said proudly - Tomorrow we will deliver once more this square to our dear people with a special reward to Professor Ventura, with a marching band and all!

Amid the applauses Professor Ventura felt a little strange again, but he thought it was because of the news of the "tribute", which usually got him tense and overwhelmed, since his modesty prevented him from enjoying it. However, what he didn’t know was that other people, without complaining, including Bart and Clarke, also felt the same strange feeling.

As the expected effect over the swallows had already occurred and it was night, the oscillator and the computer, with the complementary system, were set to a lower power level and finally switched off. After all the swallows should have already found another place to sleep! ...


It was a very important day for Tubald Weathercock. With that name, it could not have another activity, besides being the town barber, which was not to be the "tuba player" of the municipal band, the "Glorious Lemon city Musical Corporation"! Short and fat, with a thin and black mustache and hair parted in the middle, our character had an iron lung and was proudly to be the most "powerful" tuba player of all the bands in the region! (Or from all the bands of those bands, if you’d prefer ...)

After so many years without playing on the old bandstand on the square, because the swallows wouldn’t leave, he could finally "remove the rust" from his beloved instrument! He spent the whole morning polishing it while Ginevra Weathercock, his devoted wife, took care of his white uniform with the golden insignia of the corporation with more medals than a "general"!

The mayor, in his turn tested his throat, memorizing the main parts of his speech.

Meanwhile, the city employees gave a "beauty treatment" to the central square, which was abandoned for a long time, with the dirt from the swallows accumulated, as it was in sorry state!

Professor Ventura would have to go to his tribute, even hating the idea. But what worried him, and he confessed to Bart and Clarke was not this:

- These ultrasonic vibrations had a good result yesterday, but this may not be definitive! We know very little about their effect to be able to say that we have the ultimate solution!

- You mean that there might be some side effects? - Bart asked.

- Yes, in fact on the great intensity that we are using, yes! I believe that there may even be some kind of effect on people, and I would like to know more about this possibility! I must confess that during the tests I felt something weird, and I cannot tell whether they were a result of the "pie" from Smith’s dinner, or if it could be the side effect of the device! ...

Bart and Clarke, worried, realized then there was something abnormal in the ultrasound "vibrations". The boys gasped and commented in unison:

- So did we ... And we didn’t eat Smith’s pie!

The three of them looked at one another worried! ... But there was nothing that could be done now to prove it! There were only a few hours for the party, and before that the device would be connected again! ...

- Let’s worry later! If you feel something abnormal, let me know! ...

What they didn’t know, is that they would feel (oh boy!), only that there would be no time to warn! ...


In the evening, some small flocks of swallows still prowled the square, but the equipment was turned on schedule, and in time the few birds were abandoning the site. For the first time people could walk on that square, at that time, without getting hit with a so uncomfortable “splash”!

Shortly before seven o'clock, the square was crowded. Practically the whole town was there, ready to listen to the mayor who arrived pompously in an official car accompanied by his delegation: councilors, secretaries, associates, candidates for the public office vacancies, etc. They all went to the podium next to the bandstand, where the band attacked their "marching" impeccably governed by Maestro Ronald.

Tubald was proud! Focusing his attention on the many admirers, he showed it on his strength and concentration with which he played his tuba!

After the series of songs which distracted the public until the big moment, the mayor began his long speech. Professor Ventura, asked to be on the side of the "preboste" was embarrassed by the compliments.

What everyone didn’t know however is that the vibrations which had chased the birds away were also doing a slow but efficient “job” on the people! Studies had shown that very low-frequency vibrations, or infrasound, below 16 Hz cause a sense of unease and even cause vomiting and intestinal lack of control. It's called the brown noise (Brownian noise), a reference to the color of human feces. Furthermore, ultrasonic vibrations above 18 000 Hz cause sensations of discomfort and dizziness!

However, no one knew what can happen when these two forms of vibration are combined, and Professor Ventura was using a combination of not only two of them, but many! And in a totally unpredictable manner!

The Professor’s complicated device had worked very well with the ultrasonic signals, combined infrasound signals and even recordings made by Bart and Clarke.

- It will be the best! Working with the two channels and the effects multiply! - The Professor had commented when he prepared the project.

Vibrations of low frequencies modulated the high frequencies of a channel generating beats which in their turn mingled with the oscillation of other channels of the powerful sound system that had already their beats and thus generated new beats! An extremely complex pattern of vibration was created by taking over the square and invading the bodies of the people! All of this could not be heard, but was being felt: first as a mild discomfort, after it became a malaise, making it dangerous “service” in people’s bodies. Imperceptibly penetrating the guts of their "victims", these vibrations were undermining the bodies with their unpredictable consequences.

Some people felt weird, and once again the blame had been attributed to something that they had eaten:

- I think it was the cookies ... - commented Mr. Boniface, speaking on his wife’s ear, who was also feeling "weird".

- I’m not going to eat beans for lunch and dinner anymore! - Commented Steve to his friend Joe who also had a weird sense.

By then, the mayor ended his speech, and in a way that showed something unusual was also happening to him, because he was sweating heavily and his face was as red as a tomato! ...

The band then started playing one more march by John Philip Sousa ... and the modulated ultrasound seemed to accompany it, messing in a sinister way with everybody’s guts! Professor Ventura’s strange equipment vibrations were penetrating more and more in people and the discomfort began increasing more and more ... Now it was perfectly located: The intestines ... Some software theorist could say a "digestion scan" was taking place while a hardware theorist could say that "the bytes were fluidizing near the parallel output!"

But the first to be truly affected was Mr. Weathercock. Making a greater effort to play his tuba, it was normal that any organic imbalance would have multiplied effects!

Bart, who was close to the band, was the first to notice the strange behavior of the musician:

- Initially Tubald’s face was red as a ripe tomato! After some time it was totally green ... - Bart also commented:

- It looked like a color TV with problems in the chroma stage! The red (R) had already appeared, then came the green (G). Only missing the blue (B) to have a good standard calibration RGB! - Bart made reference to the standard colors of color TVs that are just shorthand for R red (red), G green (green) and B blue (blue), typical observation of those who think most of the time about electronics! ...

But the final effect was not only the sickness ... With the vibrations taking over everyone’s gut, things were getting complicated.

Professor Ventura, who was also feeling weird, soon realized what the source of the problem was, but from where he stood there was no way to do anything. He tried to make a signal to Clark turn off the equipment as soon as possible. However the state of Clarke prevented him from paying attention: the boy was already bad!

Then came the time of the last chord, and the tube had an important role in that song, producing a "F" lower and stronger! But poor Tubald wasn’t good:

He was already dizzy and unwell, he reached the limit; turning blue as Bart narrated later, and gathering all the strength that was left to not make a mistake in that final note, he closed his eyes and blew! This was too much: the effort was excessive and instead of the strong note come out on top, as it was expected, what came out was in a lower part, and it was not a musical note!

- Deleted! -it was later the comment from someone connected to computer science, referring to the fact.

The smell immediately spread in the form of a "shock wave" and it worked as a catalyst! People, who were not feeling well already, affected by the strange vibrations, including Professor Ventura, could no longer hold the cause of discomfort and the impact of the disaster was general! ... It was a much more powerful chain reaction than an atomic explosion! ... Much worse than what is taught about the brown noise.

- I begin imagining how the people in Hiroshima felt! - Commented someone with a frown when things calmed down.

Tubald was now yellow out of shame, with dirty pants, put the tube under his arms and started running as fast as he could!

The next person to be affected was the mayor! Even with the microphone in hand, he could not hold on after receiving the "shock wave" and the disaster was seen by everyone! ...

Someone less affected in the crowd still managed to react to the unusual scene screaming:

- Hey! The preboste "pre shitted himself"! ...

There was no time for laugh, because the explosive effect of the vibrations propagated, taking over the crowd! ...

The other musicians in the band, the crowd and the podium authorities panicked trying to get out of there as fast as possible, but as the floor was already dirty, as a result of the “shitting wave”, tripping was inevitable ... The "prebosting" was general ! Confusion, stink, dirt and panic! The mayor even tried to enact the state of "public calamity" while he could still hold the microphone in hand, but the uncomfortable situation he was prevented him! His first reaction after that was to run but at platform exit ladder he was pushed down by Mr. Wilder, a councilor, who was feeling so bad and in panic that his mustache usually bent down, was twisted ... The rest came as a wave: the delegation practically ran over the mayor and dispersed through the streets around the square! The mayor, in that sorry state he was, had to walk home!

The confusion was short-lived, because no one was on site to help the "dead and wounded" that by then just wanted to get the hell out of there! But the results were felt for weeks! No birds and no people, the square was completely empty, and much dirtier than before, when those ones that "prebosted" were only the swallows!

People scattered, each looking to get as quickly as possible to their houses and a bathroom. Professor Ventura had time to turn off the equipment and realizing the danger he was in, he left! Bart and Clarke also realized it was the best to leave town for a good time!

As for the equipment it was later "uninstalled" and following higher orders, escorted by the municipal guard and under the stern gaze of the mayor, it was buried in a safe place!

At the end of the ceremony, most exalted people were carrying posters with slogans like "Down with Electronics", "Down with Computerized Dysentery" or "Off with such hardware", "SEAL the Serial Outputs", applauded!

The Environment Promoter, who also "prebosted" at the crazy night, still feeling the effects of the vibrations, was very strict when ordering the permanent deactivation of the device: Dr. Lair classified it as "a threat the integrity of the planet and whose operating principle should be kept forever out of reach of mankind ... "!

They say the diagram "explosive" of the ultrasonic generator created by Professor Ventura is available on the Internet for those who want to "download" at the address "" but, given recent care disclosure of the construction of dangerous weapons and artifacts harmful to health in the network, we do not believe they have missed it! ...


Brown Noise

Technically the noises are named after colors. Thus, there is a white noise, which is defined as the one formed by frequencies which are distributed randomly throughout the spectrum, with equal intensity. Moreover, the pink noise has a frequency spectrum randomly distributed, but the intensity decreases as the frequency increases.

The name "brown noise", though it is an allusion to the effects of low-frequency vibrations (between 5 and 30 Hz) which, according to studies, cause discomfort in people to the point of inducing intestinal disorders that can lead it to out of control. The brown color, according to Wikipedia, is just an allusion to human feces. In practice, though these vibrations have even been tested as war weapons, they have not proved to be as potent as touted. Even on the TV show "Myth Busters" with a powerful testing device, the statements failed to cause the decontrol from the story. But if the reader wants to experience ... Anyway, it's a story which aims primarily to amuse the reader.