Here’s the post which contains all the results of the AOA-themed music trufax test quiz, including all the technical explanations, charts, and smug thinly-veiled shade that you crave!

Some background to this post for those who came in late – a little while ago I noticed that AOA’s Jimin and Seolhyun were being picked on for their lack of history knowledge by trashy netizens. Given the mindblowing long, exhaustive list of the ways in which both Korean and international netizens demonstrate incredibly consistent stupidity levels, it seems to me that netizens calling out Korean pop idols for a lack of intelligence is a bit like Bom calling out Minzy for too much plastic surgery. Noticing the hypocrisy of this, I threw a quiz at my readers to see how much they knew about music and sound. You could argue that music fans don’t need to know about music and sound, and you’d be right, for the same reason that someone who drives a car doesn’t need to know how an internal combustion engine works. However if music fans don’t need to know about music and sound, why do members of a k-pop group need to know about history?

Of course I could act all superior in my knowledge and criticise everyone for not knowing stuff, but that’s not my style (contrary to popular belief in some circles). Instead, rather than bully and witch-hunt others over lack of intelligence like trashy netizens who should be killed, I thought why not take the chance to educate folks about music AND about netizen hypocrisy at the same time? That’s what this quiz was really all about, and it seems that you all appreciated this approach, because this was the most popular Kpopalypse quiz ever!

The quiz wasn’t easy – only one person received a “pass mark” of 80%, but most readers averaged between 0% and 30%. Here’s a handy chart which shows how well quiz participants scored as a global average.

I now present to you the answers to the quiz. All questions were both mandatory to complete the quiz and multiple choice, all readers had to do was select the most correct answer in each case. I will provide you now with each possible option and I’ll explain why the correct answer was correct and why the wrong answers were wrong where applicable. Who knows, after reading all of this, you might become smarter than both a netizen AND a k-pop star!

Question 1

AOA’s Choa is 26 years old and was born on March 26, 1990. She skips history class to attend band practice once per week, and she has been following this routine since she was 18. At rehearsal Choa is subject to volumes of 100dB for three hours in two 90 minute sessions, with a 15 minute break in between. Given these factors, what is her most likely hearing range?

Possible answers:

20Hz-20000Hz

10Hz-15000Hz

25Hz-17500Hz

20Hz-16500Hz

30Hz-15500Hz

20Hz-12000Hz

25Hz-14500Hz

25Hz-18500Hz

15Hz-19000Hz

The answer:

The first thing to know when answering this question is that the human hearing range is 20Hz-20000Hz, and this was the answer that most people selected, however there’s a few extra things to consider here. The first factor is that people lose their hearing over time and exposure. Choa’s exposure levels aren’t that extreme (100dB for three hours a week after hitting 18 years of age isn’t that different to what anyone would experience if they went out clubbing or to loud bars once a weekend) so we can safely assume that she’d have lost hearing at the normal rate for someone her age. Also it should be noted that when people lose their hearing, they lose it from the treble end first, because the smaller hairs in the ear which reproduce treble frequencies to the brain are closer to the outside of the ear, so they get more exposure and wear out quicker. Therefore, we can disregard any option that has anything other than 20Hz at the lowest end of the frequency range. Humans don’t hear down to 10Hz or 15Hz (they can sometimes feel these frequencies but generally can’t hear them) and we can disregard all the 25Hz and 30Hz options too, this process of elimination leaves us with three possibilities:

20Hz-20000Hz

20Hz-16500Hz

20Hz-12000Hz

It’s not the first one – Choa would have experienced some hearing loss, as all adults do. It wouldn’t be 12000Hz either, that’s about the hearing range of a 50 year old – Choa would have pretty trashed ears if she could only hear pitches up to that height at age 26. So the correct answer is 20Hz-16500Hz.

How many readers were correct?

Only 10% of readers got it right. If you were one of them, take a moment to feel appropriately smug and self-satisfied!

Question 2

Seolhyun is doing vocal warm-ups. She says to you “Because I don’t go to history class, I’ve had extra time to practice my singing, and now I have a three-octave vocal range, just like IU!” She then sings the three notes from the climax of IU’s “Good Day” (in the below video from 4:47). What is she actually singing?

Possible answers:

Three octaves ascending

Chromatic scale ascending

Whole-tone scale ascending

Major pentatonic scale ascending

Minor pentatonic scale ascending

Major diatonic scale ascending

Minor diatonic scale ascending

Quarter-tone chromatic scale ascending

The answer:

The three notes IU is singing, in order, are E, F, F#. This only fits the pattern of a chromatic scale ascending, as none of the other scales mentioned have two semitone jumps in a row.

How many readers were correct?

The correct answer was the second-most popular choice, which was good to see. I was however surprised to see that over 20% of readers actually believed the hype about IU’s “three octaves”! Clearly more technical trufax posts about music are in order!

Question 3

“That’s nothing”, replies Jimin. “I’ve been skipping history class and practicing even harder than you, and I can do four octaves, just like Seventeen! Listen to this!” Jimin then sings the climax from Seventeen’s “Pretty U” (in the below video from 3:04). What is she actually singing?

Possible answers:

Three octaves ascending

Chromatic scale ascending

Whole-tone scale ascending

Major pentatonic scale ascending

Minor pentatonic scale ascending

Major diatonic scale ascending

Minor diatonic scale ascending

Quarter-tone chromatic scale ascending

The answer:

The four notes the guy from Seventeen is singing, in order, are Bb, C, Eb, F. Given that the key of the song is Eb, this spells out a major pentatonic scale ascending. The notes of this pattern also fit into a major diatonic scale ascending, but it’s not spelling out the actual scale because there is a skipped note – the D or seventh degree of the Eb major scale is skipped over.

How many readers were correct?

17% of readers got this one correct, and an equal amount oddly chose “quarter-tone chromatic scale ascending”. Quarter tone scales don’t get used in k-pop much, it’s not really a western pop music thing, and I can’t think of an example in k-pop off the top of my head. If you’re curious and would like a more general example of what quarter tones sound like, you can check them out in a piece at this link.

Question 4

You’re soundchecking the microphones for AOA, and you’ve carefully tuned the PA so there’s no feedback when microphones are used at correct volume. Seolhyun starts singing AOA’s new song “Good Luck (History Is Hard)“, and the sound is crystal clear. Then Jimin starts her rap part and instantly there is loud howling feedback. You isolate the frequency as 250Hz. The microphones are standard wireless dynamic microphones, and the group are using foldback wedges instead of in-ear monitors. What is the most likely explanation for the feedback coming through Jimin’s microphone but not Seolhyun’s?

Possible answers:

Jimin has a squeakier voice than Seolhyun which is triggering a resonant frequency in the room

Another electrical source is interfering with the transmission frequency that Jimin’s wireless microphone is set to

Jimin is breathing too harshly into the microphone, creating lower frequency distortion

Jimin’s microphone has a loose wire inside it

The foldback wedge by Jimin’s feet has stopped working and is not producing sound

The PA is too loud and needs to be turned down

The venue is incorrectly using three-phase power, mixing stage lights and audio on the same phase circuit

Jimin is holding the microphone incorrectly, blocking the air vents at the rear of the capsule

The answer:

As this question is a bit complicated, and there’s a few “close but not quite” answers, let’s go through each possibility one by one.

Jimin has a squeakier voice than Seolhyun which is triggering a resonant frequency in the room – incorrect. Differences in frequency range between different human adult voices are too slight for this to be a factor. Mathematically, human vocal tones are a lot more similar to each other than you might think, it’s only our curious human biases that are tuned to perceive great differences between the sounds of different singers. Another electrical source is interfering with the transmission frequency that Jimin’s wireless microphone is set to – incorrect. Interference from other electrical sources may produce hum, radio signal and other unwanted results, but is very unlikely to produce feedback. It’s certainly not impossible, but it’s definitely not the “most likely explanation”. Jimin is breathing too harshly into the microphone, creating lower frequency distortion – incorrect. Breath noise shouldn’t trigger feedback in a “carefully tuned” PA. Jimin’s microphone has a loose wire inside it – incorrect. This wouldn’t produce a feedback loop, it’s more likely that the microphone would cease working altogether, in which case no sound would be produced at all from it, hence no feedback. Another (much more unlikely) possibility is a short circuit from a loose wire might create a hum, but if this would be the case, the hum would be there even before Jimin stepped up to the microphone. The foldback wedge by Jimin’s feet has stopped working and is not producing sound – incorrect. A foldback wedge that is not producing sound can’t produce feedback either. The PA is too loud and needs to be turned down – incorrect. If both Seolhyun AND Jimin were feeding back, then this would be the right answer, but since it’s only Jimin, we know that the problem isn’t the PA’s master volume because a too-loud PA would most likely be affecting both of them. While turning down the PA would probably get rid of the feedback, it would also make Seolhyun quieter for no good reason so it’s not an optimal solution to the problem as it isn’t getting to the root cause. It’s the sort of thing that an audio engineer might do as a quick band-aid solution while they figured out what the real problem was, although a smarter audio engineer would turn down Jimin only, rather than the entire PA system. The venue is incorrectly using three-phase power, mixing stage lights and audio on the same phase circuit – incorrect. Three-phase power that is used in live venues typically operates on the same frequency as your power points at home, either 50Hz or 60Hz (depending on country) and so incorrect use of it wouldn’t cause feedback at 250Hz. The most likely artifact of using power in this way would be a low 50Hz or 60Hz hum through the PA’s speakers rather than any microphone feedback, and like with the loose wire scenario, this hum would be present even if nobody was singing. Jimin is holding the microphone incorrectly, blocking the air vents at the rear of the capsule – CORRECT. Why is this answer correct? Dynamic stage microphones usually have what is called a cardioid response pattern. The response pattern, when superimposed on a microphone, looks like this: A cardioid response pattern is directional, it will pick up lots of sound from whatever you’re pointing it at, and less sound from whatever is around it to the sides and rear. In a typical live venue scenario, the foldback wedges are positioned behind the microphones, between the singer and the audience in the dynamic microphone’s “dead zone” so the sound from the wedges doesn’t get into the microphone and generate a feedback loop:

That’s fairly basic, but here’s where it gets complicated, and I’ll do my best to simplify this as much as possible (tech-boffins, know that I’m leaving out some detail on purpose). Microphones work by having a diaphragm inside their capsule that vibrates when signal is received, this vibration is then converted to electrical current. Cardioid microphones derive their directional properties from the fact that air hits the front of the microphone’s diaphragm and the rear of the microphone’s diaphragm at different times, via ports in the front and rear of the capsule.

The time difference between these two collisions creates a phenomenon known as “phase cancellation”, meaning that if sound hits the front of the microphone it passes through with no issue, but if sound hits the rear of the microphone before it hits the front, that sound gets (somewhat) cancelled out.

By blocking the air vents at the rear of the capsule, now the diaphragm can no longer receive air vibration from both the front and the rear vents – only the front. This means that now the microphone is equally sensitive in all directions, or omnidirectional, because no matter what angle the signal approaches the microphone from, there will be no cancellation, it will vibrate the diaphragm in the same way. The response pattern now looks like the red circle here:

Now it doesn’t matter anymore which direction you point the microphone in – an equally-sensitive microphone will now pick up sound from everywhere nearby, including the foldback wedge, and maybe even including those annoying fangirls in the audience too. Observant readers will have noticed by now that Jimin is partially blocking the rear vents with her hand in the picture above. Jimin, like a lot of rappers, doesn’t hold her microphone correctly. That bullshit trendy way that rappers insist on holding the microphone where they cup the capsule in their hands rather than holding it by the handle actually generates a lot of feedback for audio engineers. It’s painfully ironic that in a genre where there’s so much emphasis on “getting on the mic” nobody fucking knows how to use one, but then that’s hip-hoppers and their stupidity for you. It’s definitely the most likely explanation for the feedback.

How many readers were correct?

The correct answer was the third-most popular option, with 15% of the vote. More people thought that electrical interference of Jimin’s trademark squeaky voice might be at play.

Question 5

What does the following chart demonstrate? Pick the most correct answer.

Possible answers:

Binaural beats (difference between two waveforms perceived as a separate frequency)

Fletcher-Munson curve (patterns of hearing response at different dB ranges)

Fourier transform (capturing complex harmonic resonance in a single waveform)

Phase-shifting of AC current

Nyquist-Shannon theorem (upper physical limits of pitch sampling)

The answer:

Once again I’ll go through each potential answer individually.

Fletcher-Munson curve (patterns of hearing response at different dB ranges) – incorrect. Here’s what Fletcher-Munson curves actually look like:

These curves show that because of the physiology of the ear, as dB levels increase, apparent bass levels are boosted as the ear’s response becomes “flatter”. That’s why you always have to crank your stereo really hard to hear the deep bass.

Fourier transform (capturing complex harmonic resonance in a single waveform) – incorrect. Here’s a Fourier transform:

I won’t get into the math of it all, but the short version is that several waveforms can be combined into one complex waveform without losing any of the information. In the above diagram when the three top waveforms are combined the fourth one is the result but to the ear nothing is lost. When sound hits our ears it’s all one waveform (well, two, because we have two ears) but this waveform can be comprised of many different combined signals.

Phase-shifting of AC current – incorrect. This diagram that I stole from somewhere shows phase shifting and explains it pretty well, saving me the trouble.

Binaural beats (difference between two waveforms perceived as a separate frequency) – incorrect. The following chart shows binaural beats.

If you look up binaural beats you’ll come across tons of absolutely excretable new-age bullshit because some smelly hippies took too much LSD and masic mushrooms one day and decided that listening to binaural beats opens up the third eye and lets you talk to Timothy Leary’s ghost or some fucking crap. All binaural beats really means is that two frequencies that are close together create a third “beat frequency”, which is the difference between those two frequencies. If you’ve ever tuned a guitar by ear you’ll be familiar with this sound, the rapid pulsing “difference” frequency that becomes slower and slower as your strings become more and more in tune.

Nyquist-Shannon theorem (upper physical limits of pitch sampling) – CORRECT. This is going to require some explanation.

Okay, so again I’ll try to keep this simple and explain this with a minimum of math. Digital sampling works by taking snapshots of the waveform at certain periods of time. It’s never a “true” picture of the waveform, but a step-by-step reconstruction. Think of it like taking a photograph of a painting with a digital camera – the infinite detail of the painting is reduced to a finite number of pixels, and the more pixels, the closer it will look to the original painting. It will never look 100% like the painting, but with enough pixels, we can make it look so close to the original painting that the human eye would struggle to tell the difference. With digital audio, the more steps (samples) you have, the better the reconstruction is (the more accurate a representation it is of what’s being sampled) and with enough samples you can’t tell the difference between the digitally sampled version and the original. One sample is like a pixel, but it’s a pixel in “time” rather than “space”.

The industry standard sample rate is 16-bit 44.1KHz stereo, or two tracks of 44100 samples per second, and this is industry standard because it’s the sample rate of CD playback. This means that a CD can reproduce any sound accurately up until 22.05KHz. If sampling a waveform at 22.05KHz, you would get exactly two samples per waveform, one at the top of the waveform travel, and one at the bottom, like this:

The vertical lines show when the samples are being taken, one for each peak and trough. This is enough for the digital/analog converters in audio equipment to do their job and accurately sample and reproduce the signal. However if you try to sample a waveform above the 22.05KHz pitch cutoff, you don’t have enough samples to represent each peak and trough. That’s when you get something like the diagram in the quiz. Let’s look at it again:

The bottom graph shows a fast-moving waveform, which might be going at 40KHz (just an estimate). The top graph shows how the sample software has interpreted this waveform. The waveform completes just over one full cycle between each snapshot, the snapshot points are represented by the barbs on the top waveform. Because these snapshots line up in a different pattern due to the wave moving faster than the sampler can take “photos”, the sampler thinks that the bottom fast waveform is actually the top much slower waveform. If you want a visual parallel, think about how in films wheels sometimes look like they’re turning in reverse, it’s because the film shutter speed isn’t fast enough to accurately capture the wheel movement once it gets above a certain speed.

How many readers were correct?

This was probably the hardest question of the quiz, and only 14% of people picked the right answer. The incredible amounts of nonsensical hippie bullshit that came up when quiz participants searched up “binaural beats” on Google probably contributed to the confusion, proving that lies can be very powerful and justifying the existence of posts like this one.

Question 6

AOA’s Jimin is sad because people on the Internet have been picking on her and calling her stupid because she can’t recognise Korean historical figures. She’s been crying all night and stamping the floor in tears, it’s keeping you awake! If you and Jimin are sleeping in adjacent rooms, what would be the best material to make the wall out of to put between you and Jimin to block the sound, so you can get a good night’s sleep?

Possible answers:

10cm of solid brick

15cm of solid concrete

Two 2cm panels of plywood with a 4 cm gap between them

5cm of corrugated lead sheeting

8cm of solid plywood

8cm of solid brick, covered with 3cm of acoustic soundproof foam tile

12cm of solid concrete, painted with soundproofing paint

5cm of solid glass

1cm of cardboard

The answer:

When soundproofing a room, the most important factor is not the material used – with the exception of the cardboard (which would probably just vibrate like crazy until it fell over), all of the listed materials would be fine if used in the right way. Thickness does matter to some degree but walls have to get impractically thick before you get any benefit. The most important aspect is actually physical isolation – stopping the vibration from getting from one side of some “stuff” to another. The best way to do this is to physically decouple the different materials. Every time sound waves pass through a layer of material, they lose energy and strength, so the more different layers of material they have to pass through, the better. Professional studios are often built in physically decoupled “floating” rooms for this reason. Therefore, the correct answer out of the options presented is two 2cm panels of plywood with a 4 cm gap between them, as the sound has to pass through air, plywood, more air, and then more plywood to get to the other side (and if you stuffed the 1cm of cardboard inside the air gap in the middle, it would be even more effective!). Soundproofing paint is a gimmick that doesn’t do shit, and believe it or not neither does the tile – as the soundproofing foam tile is stuck to the concrete wall it would vibrate in sympathy with the concrete, providing no soundproofing effect. “Soundproofing foam tile” is actually an unfortunate marketing misnomer – these tiles are used for sound absorption to “deaden” reflective rooms on the inside for sound recording use and contrary to their name don’t have any special soundproofing properties when it comes to noises from the other side of a room leaking through a wall, or noise from within a room escaping to the outside.

How many readers were correct?

A bell-curve like this shows to me that there was less guesswork and more certainty with the selections – pity almost half of you had the wrong answer. It’s a very understandable mistake to believe that foam tiles can soundproof a room, and even audio industry professionals make this mistake all the time, so don’t feel too bad if you were one of the 46% of respondents who took the quiz and selected this! Maybe you should feel bad if you picked “1cm of cardboard” though… just a little. Maybe you thought it was a trick question, but Kpopalypse would never be so mean.

Question 7

What is the four-chord progression used throughout AOA’s “Heart Attack”?

Possible answers:

i-VI-III-VII

I-V-vi-IV

I-vi-IV-V

I-IV-V-IV

i-VII-VI-V

i-III-VI-VII

i-vi-V-i

I-iii-IV-V

I-IV-vi-V

i-VI-VII-III

i-VI-III-IV

I-IV-vi-V

i-V-VI-III

The answer:

The chord progression of “Heart Attack”, which never changes at any point throughout the song, is Am, F, G, C. In relative roman numerals this translates to i-VI-VII-III. It’s important to note that Am is the starting chord of the song proper (the intro is ignored, it’s only for the video), which means that the song is in a minor key and so all other chords are measured as relative to Am. Those who factored in the intro might have concluded the song was in C major with the progression C, Am, F, G which would make “Heart Attack” a song in the popular doo-wop progression I-vi-IV-V. However this doesn’t make sense when listening to the song itself as Am is the first chord heard and all the verse and chorus melodies use the Am as their beginning and end point.

How many readers were correct?

Yay! A large… well okay, a slim majority of you… well okay not even really a slim majority as 89% of you actually got it wrong… but you know what I mean. The correct answer was the most popular answer, which was good to see.

Question 8

You’re walking down the street when seemingly at random, Seolhyun comes up to you and gives you a hug. She says to you “I’m so excited! They’re going to let us re-release the AOA catalog in any sound format that we want! Now us girls don’t know much about music history, but everyone else seems to be history experts, so maybe you can help us! Given the history and technical specifications of sound recording formats, what would be the best quality sound format for us to use for the physical products which we end up selling to the public, that would preserve the integrity of our original digital master recording the most closely?”

Possible answers:

Compact disc

33 RPM vinyl

45 RPM vinyl

78 RPM vinyl/bakelite

Cassette

Wax cylinder

MP3 (lossless compression)

Minidisc

1/4″ reel-to-reel

2″ reel-to-reel

The answer:

The key phrase here is “preserve the integrity of our original digital master recording the most closely”, it wasn’t a question about the “best” format, but the one which would most closely replicate the original digital master. To preserve a digital signal the most closely (i.e ones and zeroes), you need to reproduce it digitally, using the same format, or as close as you can get. So we can immediately discard all analog formats listed, all of them will introduce extra noise and artifacts to the signal and decrease the accuracy of the content – vinyl, cassette, reels and 19th century wax cylinders all get the heave-ho. This leaves us with minidisc, which is shit (lossy compression), CD and MP3. If we’re talking about preserving a digital signal MP3 is a bad idea. CD is the minimum industry standard and CD format is pretty much the same file format as the files that come out of a digital audio workstation. These days there are lossless MP3s that play sound at above the 16-bit 44.1KHz CD sample rate that CDs are capable of reproducing, but they’re honestly pointless wank. There’s a mess of technical issues which means that high-fidelity MP3 is always equal or worse sound quality than CD even if the sample rates and bitrates are higher, and I won’t summarise the reasons (you can read a very technical essay about the issue here if you’re interested) but a lot of it basically boils down to the fact that AD/DA (analog-to-digital/digital-to-analog) converters inside modern CD players are actually quite clever and do a much better job of smoothing waveforms than high-resolution MP3s do by quadrupling the sample rate. The upshot of it all is that compact disc is still (for now) the “most correct answer”.

How many readers were correct?

I guess with lossless MP3s being the newer format, people understandably thought that they would have superior audio quality to CD, but it isn’t so. Oh gosh and don’t tell the poor inventor of the minidisc that you guys think wax cylinders is a better format to preserve digital audio! If you’d like to know what a wax cylinder recording sounds like, click this link which might prove educational (spoiler alert: fermented ass).

Question 9

What is the name of the below electronic tone control device? Pick the most correct answer.

Possible answers:

Distortion

Aural exciter

Harmonic smoother

Graphic equaliser

Reverb

Power amplifier

Stereo chorus

Multipass filter

Analog delay

Compressor

The answer:

You didn’t need to be able to read electrical circuit diagrams to figure this one out. You’re looking at a circuit for a ten-band graphic equaliser. The giveaway is the Hz column on the left of the red box, which shows the frequency for each of the ten bands, and which matches pretty closely with any ten-band graphic equaliser on the market.

How many readers were correct?

Okay, so maybe this question was a little tricky. All of the options listed are real things that you can buy that do stuff, except “multipass filter” which actually doesn’t exist and is just some shit that I made up for the quiz.

Question 10

In the following picture of important historical figures in music, who is at D4?

Possible answers:

Bela Bartok

Frank Zappa

Philip Glass

John Cage

Sergei Rachmaninoff

Anton Bruckner

Arnold Schoenberg

Edgard Varese

Nikolai Rimsky-Korsakov

Dmitri Shostakovich

Maurice Ravel

Giuseppe Verdi

Igor Stravinsky

The answer:

A nice easy one to finish the survey off, as this is one of the few questions where a Google search would have given you an accurate answer. The correct choice was of course Dmitri Shostakovich.

How many readers were correct?

Even with Google Image Search at your handy disposal, only 16% of readers recognised Dmitri. Tsk tsk. That’s really bad… this isn’t even basic knowledge, it’s knowledge so basic that you’re treated like an idiot if you don’t know him. How can you even say you graduated elementary school without knowing him? I hope you’re embarrassed. He is not someone that you could laugh over and use as a joke. Don’t think you can get away with apologizing just to make this all go away. Please really look within yourself and reflect over what you did.