Electronic devices are more and more perfect every day, and it is already difficult, even for a trained ear, to distinguish between a "mechanical" sound of a real instrument and the same sound, when it is reproduced electronically. It was because of a bet about it that Professor Ventura, Bart and Bert, got involved in yet another adventure which, of course, also had the troubled participation of Tubald Weathercock, the local musician.
- That's it!
- No, it's not!
- That IS it!
Professor Ventura entered the lab, just in time to find Bart and Bert almost "hitting themselves" in a very heated discussion:
- But, after all, what is it and what is not it? - interrupted the teacher, pushing away the two boys who were already dangerously close to each other, being able to decide the matter in a less intelligent way.
Bert then explained the reason why they were arguing:
- I say that modern amplifiers are so faithful that, even the most trained of ears, cannot distinguish a real musical instrument from an electronically reproduced one! And beyond that…
Bart interrupted:
- Well, I say no! There are so small differences between the actual sound and the sound reproduced electronically that, certainly, a trained ear can sense!
Professor Ventura looked at the two and showed that he was also in doubt:
- You know what?! Modern amplifiers, such as those that use power field effect transistors at the output, can achieve very low levels of distortion, on the order of 0.001%, or a thousand times less than the minimum that can be noticed by our ears!
- Which means that we cannot notice any difference between the actual sound of the instrument and the one reproduced! - Completed Bert glaring at Bart.
But the teacher was not finished:
- However, reproduction doesn't depend only on the amplifier!
- Ahh! - exclaimed Bart, pointing to his friend Bert, as if putting him on his place.
The teacher asked him to calm down and continued:
- In addition to the speakers and sound sources, which can be so perfect that the difference would not be noticed by our ears, we have a very important factor to be considered, and that many people still discuss.
Bart and Bert, curious, asked at the same time:
- Which one, professor?
- The harmonic components which we cannot hear from these sounds!
Bart and Bert were embarrassed, but it was Bart who asked:
- That we can't hear? But, if we cannot hear, how can these "components" influence?
Professor Ventura then explained:
- Musical sounds have very complex waveforms, and for this reason, they are formed by fundamental and harmonic oscillations in great quantity that, theoretically, have frequencies which extend to infinity.
- Yes, but we cannot hear these harmonics above our hearing limit, around 18,000 hertz! Isn't that true? - asked Bert.
- We cannot hear, but it has been shown that these harmonics, even those of higher frequencies, contribute to a "colored" effect in the sounds, that is, they enrich it in such a way that our ears can perceive it indirectly, without even considering they heard, or at least it seems like that! - The professor looked quite serious.
- Colored? The only colored sound I know is that of the Tubald tuba! He turns green, blue and of all known colors when he blows that "thing".
Bart and Professor Ventura laughed at Bert's humorous comment. The professor did not stop there, however:
- Actually, there is no definition for what is the "colored" of a sound other than its own richness in harmonics. An interesting experiment was once made to demonstrate this.
- Yes? - the boys were very curious because the subject was fascinating.
- Two amplifiers, of different pass frequency range, were used to reproduce the same sound. One had only the range that we can hear but played it without distortion. The other had a much wider range, extending to 40 or 50 kHz, far beyond our hearing capacity, as well as operating with great fidelity.
- I can imagine the results! - commented Bart, anticipating what Professor Ventura would say.
- Well then! Even when reproducing sounds that cannot be heard, the widest range proved to be "richer" in reproduction, with what was called a purer "colored" for the sound. The sound was more "pleasant" or natural! For the other, the comment was that its sound seemed "harder" or more artificial!
- That's why, even if we can't hear frequencies above 16,000 Hz or 18,000 Hz, commercial amplifiers are sold with feedbacks which go far beyond that! - concluded Bert.
The professor agreed:
- Exactly! The feedback above what we can hear guarantees the amplification and reproduction of the harmonics which give the so-called "colored" to the sound, making it closer to the real one!
- Wow!
Bart thought that was enough to convince his friend:
- And then, we were convinced there are those "nuances" of the sound which a trained ear can notice, and that even with an amplifier that reaches 40 kHz we will have even higher harmonics which may be missing! Would they be enough for a trained ear to recognize them?
The other answer showed, however, that he had not changed his mind:
- I doubt it!
They were about to start a new discussion, when Professor Ventura, separating them, made a suggestion:
- Why don't we do a test?
The two boys stopped quietly and thought: “It was a good idea to clear up any doubts, but what kind of test could they do?”.
The teacher had the answer for everything, and it would not be very difficult to "come up" with something which would also work to clear a doubt that was his own:
- Faithful devices, we have: a powerful 150-watt amplifier with power MOSFETs and with a 16 to 100 000 Hertz pass range, distorting only 0.001%. An excellent fidelity speaker, too! Only the signal source and the "trained ear" are missing!
Bart agreed, thought for a while and finally found what was missing from the experience:
- The signal source, we also have, my electronic synthesizer. As for the trained ear, I know a pair, but it's not here at school!
Professor Ventura and Bert then realized what Bart was thinking and completed at the same time:
- Tubald Weathercock!
Yes, nothing better than a musician, a tuba player proud of his skill as the "most powerful tuba" of all the bands in the region, to have the sensitivity and competence required for the event.
Bert was about to run after Tubald when Professor Ventura stopped him:
- Wait! Where do you think you're going?
- Well, invite Tubald to help us with the test! He will be proud!
The teacher asked Bert to calm down, and after telling him to sit back explained:
- You're doing things wrong! If you invite Tubald to help us in the test, with his "trained" ear, he is proud of his non-electronic instrument, and of the music played in the analogical way, even if he doesn't feel any difference, he won't admit it!
- It is true! - agreed Bert more calmly.
But the teacher knew how to do the "thing" the right way!
He then suggested a test be done, but without Tubald knowing it. The musician would make the judgment, but without being aware of it, so that he would not interfere with the result! This way, it would determine whether or not there would be a difference between the "live" sound of an instrument and the "recorded" sound of the same instrument!
- But how?
The teacher sat down and calmly explained what he wanted:
- Listen!
The plan was very interesting, mainly because it also involved a kind of "prank" that they would do with Tubald. Bart and Bert liked this part more.
- Wow! Nice! Mess with Tubald and his tuba!
- Great!
Evidently, the joke was totally harmless and would not displease Tubald, who had a good natural mood for these things. After all, they would not offend him or cause any damage to his beloved instrument! What was not in the "program", however, is that the results could be slightly different than planned!
So, let's explain what the three were up to: Bart and Bert were going to install in an empty house of an acquaintance, a very high-fidelity amplifier with excellent speakers and a signal source which produced the sound of a tuba.
The source was a powerful keyboard synthesizer, which was able to perfectly imitate over 100 musical instruments! Many said that it was impossible to distinguish the sounds of the keyboard from the sound of imitated instruments when the reproduction was done in a faithful amplifier, with boxes of good quality. It was what they wanted to see!
The house was right on the path that Tubald took every day, from his home to the barber shop. For those who don't know, the tuba player, professionally, was the Lemon City's barber, the quiet city where the story unfolds. The idea was to activate the keyboard, by remote control, at the exact moment of his passage, reproducing the sound of the tuba, which he knew so well. Studying his reactions, he could know if he was recognizing the sound as "natural" or "artificial"!
- Natural! - said Bert.
- Artificial! Want to bet? - replied Bart.
- The bet is on! Whoever loses will have to listen to Tubald's tuba at the square for two weeks!
- And applaud! - Bart completed, extending his hand to seal the bet.
The bet had been placed, but there was still a problem:
- But the sound? Who will produce the sound? - asked Bert.
Bart, who knew a bit of music and handled the keyboard with some skill, was not concerned with this detail:
- It'll be easy! Every time Tubald rehearses in his barber shop, he "warms up" with a sequence of notes that starts from a more serious C, goes up to the end of the scale, and then comes back! Something like: “dó, ré, mi, fá, sol, lá, si, dó” and again in the reverse order: “dó, si, lá, sol, fá, mi, ré, dó”. He does this several times and I would be able to play it on the keyboard!
- Damn it! It will sound like someone is "rehearsing" tuba, and imitating Tubald! - concluded Bert.
- That's exactly the idea!
It was then that the teacher showed the true "depth" of the prank.
- If he hears the sound, he will certainly want to know who it is! If he is able to realize that it is "electronic", he will not worry too much! But, if he thinks it's another tuba player in the city then! …
In fact, Tubald was extremely proud of his position as the "most powerful tuba" in the region and did not admit to being "challenged" by any other musician. For him, it would be the "end of the world" to appear, especially in his city, someone who "dared" to play the tuba stronger than him!
- As long as my lungs hold, in that band, only I play the tuba!
- Calm down dear! - Ginevra tried to calm him down - You were, you are, and you will always be the best! There is no tuba better than yours!
Tubald, proudly, stroked his tuba, eventually removing a spot that impaired the powerful instrument's impeccable brightness.
But what really matters is what Bart and Bert, with the help of Professor Ventura, prepared to "clear up their doubts", using Tubald.
In the empty house, which had a huge "for sale" sign for a long time, and which was owned by an acquaintance of Professor Ventura, they installed all the "tuba simulation" equipment.
- An electronic tuba! - was the final name given to the project, by Bart.
The equipment consisted of a synthesizer, an amplifier of very high fidelity, with power MOSFETs and a box of stupendous quality, of the school's sound equipment. All of this was activated remotely by means of a remote control.
The synthesizer had the characteristic of being able to record a song and play it when activated, and the idea was to do it by radio remote control, very efficient.
- When we activate the remote control, the system produces musical sequences of tuba, as if someone were rehearsing, in exactly the same way as Tubald! - Bart commented, proud of the project.
- We can stay hidden on the opposite side of the street, where there is a vacant lot, and watch Tubald's reaction!
- It will be interesting! - concluded Professor Ventura.
Tests with the equipment, before being installed, showed that it was not possible to distinguish the synthesized sound of the tuba, from a real tuba, at least for them!
- Perfect!
At the house, everything was hidden, as they did not want Tubald to see that the sound was "electronic". He should deduce this, if possible, and thus prove the theories of Bart or Bert related to electronic reproduction.
So, they placed the box in the front room, which should have the window open when Tubald passed, but hidden under a "fake sofa" and passing the wires through the corners, they connected it to the equipment that was hidden in a small room in the back (which would be closed!).
Everything was ready and set.
Early in the next morning, within the scheduled time, Tubald came from his house, carrying his inseparable tuba, happily whistling a march by John Philip Sousa (*), towards the barber shop. The presence of the tuba was easily explained: after his work, he would play in the band.
(*) John Philip Sousa was an American composer of Portuguese origin who became famous for his band music, intensely played by military bands, such as “Star and Stripes”, often mistaken by the American national anthem.
As he passed by the house, he noticed slightly that the "for sale" sign had finally been removed and the front window was open. He looked curiously and thought satisfied:
- Great! It is sold! But who are the new residents?
He slowed down to take an "indiscreet" look to see if he saw and knew anyone, as it looked like they were cleaning the property before the move.
As he saw nothing, he accelerated and went on his way normally. However, a few steps further, a sound very familiar to the musician came directly from the front window of the house:
- Oompah! Oompah! Oompah! ...
The musician choked, tripped, shivered, and almost dropped his tuba! He immediately flinched and stopped!
Before turning, again, the unmistakable sequence of notes for a tuba was emitted, and with a power that surprised the musician!
- Oompah! Oompah! Oompah! ...
Tubald still paralyzed, came out of his trance and, turning slowly, opened a big smile, commenting softly:
- Tuba! A bass-tuba! And the "guy" is "potent"! Who will it be?
He walked back slowly, peered over the wall, very curious, waited a little, but nothing!
- Stopped! - commented Tubald - Never mind! Then I find out who it is! There is someone I would love to meet! ...
He went on happily until a terrible thought occurred to him:
- Damn it! If this guy is as good as he sounds, my position in the band is in "danger"!
Gripping his tuba firmly, his expression was no longer calm, but very concerned! The smile disappeared, and Tubald started to sweat! The perspective of losing his place in the "Glorious" Musical Corporation of Lemon City seemed terrible:
- It's the end of the World! I need to know who this "guy" is!
Finally, shaken, crestfallen and sweating, a very concerned musician went off to the barbershop. Professor Ventura, Bart and Bert who were in the vacant lot followed everything:
- He realized it's electronic! Didn't I say? - commented Bart.
- He didn't notice! If he had noticed, he wouldn't be so worried! - Bert disagreed.
- Calm down! He really felt something different "in the air", but we can't say what it is! - The teacher calmed the two of them. - We need to continue with the test.
Tubald, however, was suffering! After cutting at least two customers, he apologized for his nervousness, closed the barbershop and went home. On the way back, he did not fail to take a look at the sold house, which now had its front window closed.
- He or she must be gone! But who would be this "bastard"! - Tubald said this angrily, willing to find out who the "cheeky, who would be wanting to take his place in the band"!
- I need to be on my guard! - he thought, walking in a hurry.
At his home, he had to be calmed down by his wife Ginevra who only managed to stop him pacing back and forth after she said:
- Calm down, sweetheart! You don't even know who it is, and you're already thinking that this person wants your place! Why don't you find out who it is before worrying, and what intentions they have?
Tubald, finally calmer, agreed:
- It is true! I'll find out who it is!
The following day, the musician went to the barbershop, calmer, still carrying his tuba, but this time with a plan: spy on the "house of the tuba", as he started to call it intimately.
Again, upon reaching the site, he slowed down. Bart, Bert and Professor Ventura, who knew Tubald' habits, were on duty in the vacant lot:
- The window! It's open! There are people! ...
He spied with undisguised curiosity, he even stood on tiptoes, because he was short, after all, and there was no one around, but he saw nothing! ... He decided to move on, but very slowly, and that was when Professor Ventura, with Bart and Bert, in the vacant lot, activated the remote control:
- Oompah! Oompah! Oompah! ...
Tubald almost collapsed! He shuddered, and when he managed to master himself the sound had stopped. But he still came back!
- "Calm down Tubald! You will find out who the bastard is!" - thought the musician, trying to control himself.
In front of the house, he tried to open the gate. It was locked! He had no doubts: as he was short, he jumped with agility, even carrying the uncomfortable tuba.
The teacher, Bart and Bert watched everything.
Tubald, carefully went to the front window and looked: nothing! Then he slowly went around the side of the house and clapped his hands.
At that point, Bart and Bert, using the second channel of the remote control, put into action a device they had installed to discourage the musician from entering the house: a very real recording of the bark of a huge watchdog!
- "Ruff-ruff"...
Upon hearing that, Tubald who had a "damned" fear of dogs, ran! And how he ran!
- Wow! There is a dog! Hold it please!
But there was an obstacle to his quick exit: the gate, which seemed low on the way, for a terrified "guy" carrying a tuba, and without time to think about the movements that should be used in overcoming, was a problem! The clumsy musician at high speed, put one hand on the gate and jumped, but as the impulse was too much, he went up too far and "flew", with tuba and everything, falling on the other side!
He didn't get hurt, but he got frustrated!
Stood up. He checked that he had not damaged his precious tuba and waited for a while, but no one went out to serve him and there was no dog! The musician was surprised:
- There's something! Why don't they answer?
He clapped again at the gate, but no one answered.
Now, very suspicious, he decided to leave. He would return on another occasion, or he would seek to know directly from Cameron Lance, the previous owner of the house, who was the "bastard" of the tubista, who, after all, was a "coward" and "let loose" a dog behind him!
- Yes! That's right. He's a coward, because I think he saw my tuba or knows me and was afraid to face me! - thought Tubald. He still shouted into the house:
- Coward!
Professor Ventura, Bart and Bert, could not contain themselves, laughing softly.
- Shall we trigger the "tuba" again? - asked Bert, when Tubald was already walking away.
- Yes!
And that's what they did:
- Oompah! Oompah! Oompah! ...
A new shock for Tubald, but this time he stopped in a different way from the other times:
- Oops! There is something! This "tuba" is sounding a bit strange!
He remained still, as if waiting for a new ring. The way that "tuba" sounded seemed "too weird" for the experienced musician, even though he was a little shaken by its presence.
- Go! Play again! - he said quietly without turning around, but paying close attention.
And the electronic tuba played again:
- Ah! - exclaimed Tubald with a strange smile. Then he went on his way.
- He suspects something! - said Professor Ventura, watching the musician disappear around the corner.
- Didn't I say! - exclaimed victorious Bart, glaring at Bert.
- The "thing" is not over yet! Let's find out what Tubald thinks of the tuba.
They found Tubald working normally at the barbershop. Bart and Bert sat in the waiting chairs, and after half an hour the customer left, happy as always. The musician was also perfect as a barber and was proud of that.
- The next! - called Tubald, as a barber.
Bart sat on the chair, while Bert waited. Pretending to read a magazine, he just watched. Bart started the conversation while doing his haircut. As agreed, Professor Ventura also went to the barbershop and, after greeting the boys and the barber with some surprise, sat down to wait his turn.
- Have you heard that they sold Lance's house, Tubald?
Upon listening to that, he shivered, but he did not lose control:
- It was good for you to say that! Do you happen to know who is the new resident is?
Tubald stopped cutting Bart's hair. It was clear that he was very anxious for the answer.
- They say it's a musician. Is it true? - replied Bart, pretending indifference.
Tubald was not affected:
- This I know! But this is no ordinary musician!
- No?
- That's right! I heard the "guy" play, in fact it seemed very strange the sound of the instrument! - commented Tubald, continuing to handle the scissors with skill.
- Strange why? After all, what instrument does he play?
- Tuba, or better… something that tries to "imitate" a tuba! I even think it has something to do with me, because it only plays when I pass by, and when I looked for them, they hid!
- Now, how is it possible to distinguish the sound of a real tuba from a "tuba imitation"? - Bert, already worried, interfered in the conversation.
Tubald stopped, and proudly, to demonstrate that he had a "differentiated" ear explained:
- That is not a tuba! It sounds like a recording, or something "artificial", because it is a "harder" sound. A real tuba has a "richer" sound!
Bart looked at Bert "victoriously".
- I don't understand! How can a sound be "richer"? - in fact Bart was trying to get more information from the musician-barber.
- There is something different! It is not possible to describe it, but yesterday when I heard that sound, I could clearly see that it was "artificial", that is it! Artificial! - Tubald, standing still, stared at nothing, as if trying to "feel" the sound he was trying to describe. However, this was not possible, but Bart and Bert had the distinct feeling that, for the musician, the slightest differences between an artificial and natural sound, especially of a tuba, were sensitive.
Professor Ventura, who until then only listened to the conversation, could finally intervene:
- It's proved! - he said finally - That a trained ear can distinguish the differences that exist between the reproduction of an instrument in an electronic equipment and the instrument itself, because they really exist! And we owe this proof to Mr. Tubald, is it not?
Tubald, surprised, did not understand what was going on. Professor Ventura then explained what they had done. The musician was not bothered, mainly by the praise that the teacher gave:
- Only an accurate ear like yours could help us to unravel this mystery!
Proud, the tuba player could then draw his conclusions:
- Then, that's it! Really, I could notice there is a difference between real and artificial sound, but if you ask me why, I can't say! Perhaps Professor Ventura, as an expert, can explain.
The professor then confessed that he had a theory:
- The source of the difference may be in the way the sounds of musical instruments are reproduced or synthesized by electronic equipment. Imagine recording the sound of a tuba! How do you think it should be made to be perfect? - asked the professor, looking at Bart. The boy thought for a moment and replied:
- Naturally, placing a microphone in front of the tuba, and this microphone must have the highest fidelity possible, that is, it must provide a signal at its output whose waveform corresponds exactly to the sound it captures from the tuba!
- Right! - agreed the Professor. - And, the reproduction, to be perfect, how should it be done?
Once again Bart answered precisely:
- You must use a faithful amplifier and a speaker that produces sounds with the same waveforms captured by the microphone, that is, that correspond to the tuba!
The teacher raised his finger as if denying everything and then made a surprising statement:
- That's the difference! The sound that the microphone "picks up" when recording a tuba is not exactly the sound that comes out of the tuba, but the sound that reaches the microphone! In the way, a lot can happen. For example, the tuba geometry itself can contribute to changes. The metal edges of the instrument diffract the sound, as they are waves, and the different frequencies have different irradiation patterns!
- Of course! The sound picked up by the microphone, or even by many microphones, corresponds to a specific situation and not to the ambient standard. It is an "ear" placed on the spot. - Bart agreed.
The teacher continued:
- Exactly! This way, the "pattern" that is recorded like a tuba is not the "spatial" pattern, but what arrives altered in the microphone. This means that, in reproduction, however perfect it may be, we do not have the signal that corresponds to the sound that comes out of the tuba, but that which reaches the microphone, and this has differences!
- Wow! I begin to understand! - said Bert, now more aware of his assessment mistake.
- And there's more! The speakers that will reproduce the sound, even if they receive a waveform that corresponds to the real instrument, do not have the same pattern of directivity as that instrument: the sounds are not irradiated as they would be if they came out of a tuba, but from a speaker, and then we have new differences.
- Not to mention that this sound that reaches the speaker is the already altered signal captured by the microphone! - completed Bart.
Bert then concluded precisely what was happening:
- I'm beginning to understand! The "artificial" sound does not match what comes out of the instrument, but what comes into the microphone! And the microphone is a point pattern. For the reproduction to be real, it would have to portray a spatial pattern, so that in the speakers all audible and inaudible frequencies would spread according to a spatial pattern, similar to that of the tuba!
- This shows the complexity of reproduction necessary to obtain the real sound! - added Professor Ventura - I think that much technical progress is still necessary for the sound systems to reach this point!
- And I thought we already had the most of it! - Bart was amazed at what he thought was the ultimate in reproduction.
Tubald, proud to have demonstrated the "superiority" of the sound of his "natural" tuba in relation to the artificial one, even without having understood much of Professor Ventura's technical explanations, and still relieved to know that there was really no competitor to try to take him away from the band, decided to come home early and give the "good news" to his dear Ginevra. He wouldn't call: He wanted to do it in person!
Closing the barber shop, there went the musician with a tuba under his arm, heading for his house, whistling another very well-known march by Sousa.
He was passing by the old shed, next to Doctor Cattleson's veterinary clinic, when a different sound, actually very strange, caught his attention:
- Mooorghoo! ...
Tubald stopped, because he had never heard anything similar in his life, and immediately thought:
- Natural or artificial? It must be another test of Professor Ventura!
He waited a little longer and heard again:
- Moooorghoooooo! ...
- Ah! It's artificial, this one I know! - and going directly to the door of the shed, Tubald opened it, hoping to find another "beautiful electronic sound reproduction system", the work of crazy Professor Ventura, but what he saw was none of that! The sound was "natural" and produced by the brave Candie cow, famous throughout the city, and who was waiting for the moment to be examined by the vet due to a strange hoarseness, perhaps caused by some throat inflammation! The animal, with the opening of the door, was overshadowed by the reflection of the tuba, and that was enough to enrage it. Before the cow's threatening gaze, there was only time for a Tubald reaction: it was the musician's turn to produce his sound, which couldn't be more natural:
- Aaaaaah!
And, running away, with the brave animal chasing him, he ran a kilometer and a half to his house in record time!
Professor Ventura, upon learning of what happened, could only comment in a relaxed manner:
- Such a trained ear deceived by an aphonic cow!
Bart and Bert laughed.
