Archive for January, 2007
Some people have been asking for this for a while, so I’m finally writing it. I have a severe bilateral high-frequency hearing loss. What does this mean? What does it “sound like” to hear like that?
My short answer is that I really can’t tell you, because this is the only way I can remember ever hearing so there’s no basis to comparison. But I can show you quantitatively and let you figure out the rest.
First, in order to more quantitatively understand what I’m talking about, here is a picture of my audiogram. It is basically a plot of the frequency response of my auditory system; in other words, it’s a low-pass filter compared to normal hearing, and this picture describes what I can’t hear.
The purple box represents the range of volume intensities and frequencies that a normal person should be able to hear; low frequencies are to the left, low volumes (amplitudes) towards the top. The green line on top is a normal hearing profile - what normal people are able to hear. The dark pink line is my hearing profile. The shaded pink area is what most people hear that I can’t.
Here it is overlaid on some common sounds.
Amusingly, the piano (in green, my instrument of choice) straddles the line squarely between what I can and can’t hear. It means that I transpose passages an octave down when I’m practicing sometimes so I can hear if I’m making mistakes. When I was very small, I used to ask my mother to listen to me play and tell me if I was hitting the wrong notes. It also means that oftentimes I can’t hear my right hand playing because the left hand’s chords (or even the percussive impact of the key mechanism itself) drowns out the actual melody line.
I’ve also blocked in English speech sounds in red. Note the difference between the voiced consonants on the left and the unvoiced ones on the right. Vowels fall under my hearing range, consonants often don’t - which is why I have a “deaf accent” but perceive myself as speaking the same way as everyone else. I usually don’t pronouncing the high frequencies I can’t hear (I am trying to make a habit of it, but it’s easy to slip, and it feels really funny when I do it because I’m not used to the air moving that way inside my lips).
Most of my friends describe my “accent” as “fuzzy” or “dulled” - well, that’s what happens when you low-pass sound. Try talking using mostly vowels and voiced consonants (described below) and you may have a rough approximation of how I speak.
This is also one of the reasons lipreading is a pain, because - well, look in the mirror and say the words “big” and “pig.” Can you tell the difference? (Try holding your throat with one hand to feel the vocal cords vibrate.) One is voiced and one is unvoiced.
Try “key” and “gee,” “sip” and “zip”, “to” and “do” - and then take a look at this page about Japanese voiced and unvoiced consonants. It was one of the first things that struck me when I studied the language in high school. The only difference between the “t” and “d” sounds (and the other pairings above) as written in Japanese phonetics is the addition of little hash marks in the upper write of the katakana (alphabet) symbol.
Hopefully I’ll be able to post a file about what it sounds like to hear like Mel soon, if my tinkerings in SigSys go rewarded.
Sunday, January 28th, 2007 | Uncategorized | 4 Comments »
One of the great things about having engineers for friends is that they can imagine in tech - a blue sky brainstorming session about filter design makes perfect sense in the right group. So it’s David Klempner (UIUC ‘06) that I’ve got to thank for the following kick back onto my original SigSys project path, abandoned two years ago.
Simply put: Make hearing aids that don’t stink. (Or ones that don’t stink for me.)
Since the traditional “why don’t we amplify selected frequencies?” method doesn’t do much for folks with a hearing profile like mine where the upper ranges are essentially gone (I’ve heard that mine is the worst kind of hearing loss to make hearing aids for), I’d been trying to come up with ways to interpret a full normal-human-hearing frequency range of sound within my limited frequency range of hearing.
It’s like suddenly having the bandwidth of a communications channel halved, but having to transmit the same information. Fortunately, things like the English language are coded with plenty of redundancy, so there’s wiggle room that enables me able to understand speech. For more information on this, check out What It Looks Like To Hear Like Mel. Basically, I look like a first-order low pass filter.
The audiograms (graphs) in that post were generated via hearing tests, which mostly involve beeping various frequencies at different volumes into headphones and you indicating which ones you can hear (press a button, raise your hand). It’s a sort of primitive way of determining a person’s FIR, because as a kid I swore I could hear the little microphone and equipment clicks when they try to test the high frequencies. I couldn’t hear the notes, but I heard the tiny pop similar to the one that happens when you turn on a microphone hooked up to a great big speaker (not entirely sure what causes the impulse in the circuit, but the pop is the response of the sound system settling down from it).
Also, the “raise your hand if you hear” is subject to all sorts of experimental problems because people are inconsistent, easily confused, and… ah… cheat. (Hey, I raised my hand when I heard the microphone clicks, because I wanted to be “as hearing as possible.”) It would probably be more accurate to measure brain activity (which, as Raymond’s first lecture mentioned, also depends on SigSys - the stuff is everywhere). Anyhow, conversation went something like this, with my first chime-in being a laundry list of hearing aid schemas that aren’t straight amplification:
David: The obvious thing to try would be outright compressing frequencies downwards; it would make everyone sound weird but you might get more useful information out of it.
Me: A few years back I tried all sorts of funky little things [as alternative hearing aids] - compressing all frequencies down, folding higher frequencies, modulating all frequencies above a certain cutoff downwards…
David: You were, in fact, both compressing and correcting for the volume and
speed effects, right?
Me: Uh….
So David suggested this:
I’d start with whatever sampling rate your [laptop] hardware supports (presumably there’s an LPF there for anti-aliasing purposes), and then compress that down by a factor of two. Or, for that matter, maybe less than two; a 20% compression might give you a noticeable improvement without as much distorting effect. (eg, people’s voices still sound human.)
Cool - a starting point for experimentation.
Sunday, January 28th, 2007 | Uncategorized | 1 Comment »
Remember the little Echo robots that Eric, Joe, Andrew, Gui, and myself were working on?
We’re on Engadget.
And we leave for Japan to present the idea on Tuesday morning, which means that tomorrow is going to be spent in a flurry of phone calls, emails, and requests for advice. Lots of advice.
Sunday, January 28th, 2007 | Uncategorized | 1 Comment »
I’ve been quiet on this blog lately, mostly because I’m auditing Signals and Systems, starting my very cool AHS capstone which is on the ECS curriculum and soon-to-be textbook, and going mildly overboard for the MetaOlin Independent Study. Yes, all those things are separate blogs (so far). It’s going to be a fun semester and a fantastic demonstration of spiral learning; this is the 4th time I’ve attempted to learn SigSys and the 3rd time I’ve gone through ECS, and they just get more beautiful over time.
For the record, I nearly failed SigSys and ECS the first time I went through them, so my “OMG IT IS PRETTY!” may just be a symptom of things finally seeping through my thick, thick skull, and everyone else may have picked up on the prettiness the first time they went through it. I also tend to be really bad at learning things that I’m being required to learn but excellent at learning things that I’m either piddling around with or need to teach, so that may have something to do with it.
And now the actual content of this post which addresses its title. I met with my AHS capstone mentor yesterday. He is awesome for reasons I’m sure I’ll explain later. In the midst of our conversation about textbooks, he mentioned that it would be a good idea to have students work as “testers” to review draft chapters, and that it was generally a good idea to read the textbook before the lecture and have students take notes or solve problems in it, instead of after the lecture (which is what hypothetically happens in college classes) or never (which is what actually happens).
“Oh,” I said, wincing. “We tried that my freshman year in physics where we had to do this thing called WebAssign before class, and most of us hated it.”
“That’s why I’m not asking them to read the textbook before class,” he said. “I’m asking them to review it.” I must have looked confused then, because he explained that the psychological positions of the student are completely different in both cases. As a reader in the “Answer These Questions Before Class” situation, they’re placed in the tough spot of having to give The Right Answer in an area they’ve presumably never studied before. As a reviewer, they are experts; if they say an area is confusing, by gum it is confusing, and it’s the textbook’s fault, not theirs. Their questions are illuminating and helpful, not “stupid.” Some students who think they’re “bad at math” are really victims of textbooks that are “bad at teaching.”
I couldn’t help but think of Olin, where we’re supposed to be guinea pigs for experimental teaching methods and courses, and where we’re supposed to give feedback on these classes all the time. Do you learn better as a guinea pig? Are the good results we’re getting on student learning because the experiments are working, or because they are experiments?
Is being a guinea pig a valid teaching method to test? I think it might be.
Saturday, January 27th, 2007 | Uncategorized | 1 Comment »
Yesterday we did some more things with complex arithmetic, taking a look at how some simple operations result in surprising things. For instance, take 1/j . Multiply both sides of this equation by j/j and you’ll get j/j^2, or j/(-1), or -j. So 1/j = -j. Weird, if you’re used to conventional real number arithmetic.
Oh. What is j? It is the variable representing the square root of -1. You may know j better as i from your past math courses, but it changed its last name when it immigrated to EEland, since electrical engineers usually reserve i for the variable describing current. It’s used in complex numbers, usually written with the variable z, in rectangular form (z = a + bj) or polar form (z = Ae^(j*theta). You can switch between the two by plotting them on a graph and using trig identities. This is a terrible explanatory graphic. All radii (radiuses?) are 1, and the angles are supposed to be pi/4 (45 degrees), 2*pi/3 (120 degrees) and -3*pi/4 (-135 degrees); I’ll let you match them up.
Diana handed out some worksheets for us to follow along in class with. There were unsolved equations on one side and blank spots on the other, and we proceeded to go systematically through them in lecture format. I really like this teaching strategy; it gives you a map of where the lecture is going to go, the blanks give you something to participate with while you’re filling them in, and afterwards you have a nice record of what you’ve learned. A few changes I would make, though:
Scrap the lecture and just give us the worksheet. This would probably necessitate the creation of explanatory text around the formulas to deliver the content Diana did in her lecture, but we’d be working in groups at our own pace and free up the professors to wander around like they did in the latter half when we were just chugging on problems. This is how I was taught math in high school, and I absolutely loved it.
Make the worksheet in LaTeX instead of Word. Not a big deal, but the typesetting you get from TeX is typically nicer than MS Equation Editor. It’s one of those “it’s made already so it’s fine, but if I was making a new one…” little things.
For instance…
In other news, I can’t do arithmetic any more, and I’ve forgotten the exponential identities for sine and cosine. I also spent most of the lecture before last (Wednesday) trying to derive the concept of Taylor series from scratch because I’m trying to remember where Euler’s identity comes from; it’s the same thing that the formulae Ae^(j*theta) = A*sin(theta) + j*A*cos(theta) comes from and we see that ad nauseum in SigSys. I refuse to look it up in the textbook. So far I’ve been able to derive MacLaurin series, which are Taylor series with a=0, starting from just definitions (…yeah, I went back all the way through calculus and the definition of the derivative; that’s why it took the whole lecture). I can feel the rust flaking off my brain.
I wish Blogger did equations. I may switch to Wordpress or something that has a mathML or LaTeX plugin because of it.
For the record, I usually don’t listen to lectures; they provide a pleasant background noise while I plug on random problems that catch my fancy. I ought to go to them more often, though; they’re a good way for me to make sure I have time set aside for work, and being half-aware of them reassures me that I’m (probably) not missing anything, or that I can ask people about stuff in the lecture afterwards.
I’m not sure whether I would have this severe of a visual learning style if I actually had a functioning auditory pathway, but as it stands it’s easier for me to read things than to listen to lectures, which… is, as Eric VanWyk just walked through the lounge and pointed out, probably why I suggested the “scrap lectures and give us worksheets” method above. I do benefit disproportionately from it (mostly because I’m at such a disproportionate disadvantage already in lectures), but from past experience in high school I think it helps hearing people as well. I wonder if there’s a way to make textbooks and worksheets better for auditory learners. Hmm.
Saturday, January 27th, 2007 | Uncategorized | 1 Comment »
I’ve seen a variant of this diagram in every SigSys book I’ve found (a grand total of 3, but… hush).
Basically, signals go into systems, and new signals come out. When they go in on the left side, we usually call them X; the output of a system is usually labeled Y. Y? Dunno. Anyhow, signals can be functions, or they can be discrete or continuous. Discrete functions have values at certain time steps, and that’s it; continuous functions have a value at all times.
And then there’s this diagram, which you also see a lot. I’m going to be a bad engineer and not label my axes or anything. It’s a sketch.
Or in other words, equalizers (this is just a high-pass, you can generalize).
Diana opened class on the first day by playing us music (a signal) and showing us what it sounded like after passing through different filters (systems). First, the signal. (This isn’t actually the one Diana played; it’s what I had lying around. I don’t know what song either is.)
The image quality makes my eyes hurt, but you can click on the picture to see a less-awful version. The green thing on the bottom is called a spectrogram, which is basically “continuous sheet music that’s very hard to read.” See hackish overlay of notes on top. Both sheet music and spectrograms tell you what frequencies are going at any given time, how long they are going for, and how loud they sound (fortes and accents in the sheet music, bolder colors for louder notes in the spectrograms). Anyway, this is a signal. And now: signals… the filtered versions.
Roughly translated to piano, high pass, low pass, and band pass mean “play the right hand”, “play the left hand”, and “play only the notes you hit with your thumbs. (”Pass” refers to the frequencies you allow to pass through.)
In reality, it sounds more like this, especially if you have a lower-order filter. They don’t actually cut off the frequencies with perfect clean-ness, just more fade ‘em out over time. This is why the little diagram of the filters (the red and green picture above) isn’t a nice sharp step function, but a sort of funky little curve.
Another cool thing about the sheet music analogy is that the Fourier transform actually makes sense. The transform depends on the orthogonality of sines (which we had to prove in PDEs; I will see if I can dig up my chicken scratch on it) and says that you can split any signal into sine waves - or in other words, frequency components… or in other words, notes. This is a piece of music, but at any moment you can stop and say “hey, look at the keys (frequencies) I’m pressing on the piano” and break the chords down into individual notes. Fourier transforms take a signal in the time domain and transform it to one in the frequency domain, and vice versa. Kind of like saying “Ok, I can look at my music in terms of when I’m playing the notes, or in terms of what notes (frequencies) I play most often.”
We also talked about complex arithmetic, which I won’t write about now because it’s basically “do you remember how to convert between polar and rectangular coordinates?” right now.
Wednesday, January 24th, 2007 | Uncategorized | 1 Comment »
It’s about signals (streams of data) and what happens to them when they pass through systems (things that transform signals).
This might be more helpful, though.
A list of signals and systems that act upon them
- A picture and a photoshop filter.
- Music from an electric guitar and the wah pedal that bends the sound on the way to your amp.
- The bumps on the road your bike runs over and the dampening effects of the shock absorbers, tires, seats, and tubes that keep your bottom from being rattled sore.
- The flame of an erratically sputtering camping stove passing through the thick metal of your dutch oven so that your potatoes experience a slow, steady warmth.
- The retinal image you have of an initially dark classroom when someone suddenly flicks the lights on, and the actions taken by your eyes and brain so that you can see again in the blinding, blinding photon flood.
- A hungry frog watching for the fast black dot of a fly against the slow, waving background of leaves in the wind.
- This is somewhat sketchier: lots of student feedback on the recent occurrences in a course, and the winnowing and distillation process the professor needs to do with this input so they can make long-term corrections to address it.
- A piano with broken keys, so that it only plays some of the notes you press down.
Wednesday, January 24th, 2007 | Uncategorized | No Comments »
Yeah, I know, I’ve taken this class already, two years ago.
But I didn’t get it then.
And I want to get it now. Behold the power of spiral learning. I’m hoping that another pass will really make things click for me - I’ve started to see the fuzzy edges of why Signals and Systems is so awesome, but I can’t wield its tools with impunity yet.
I’ll be posting my notes here. They won’t be class notes per se, but random excursions and variations on a theme - my way of jumping off more and exploring around, since I didn’t do that the first time through.
Wednesday, January 24th, 2007 | Uncategorized | No Comments »
Some things that vaguely swim to the forefront of my consciousness once in a while, and that I’m keeping my eyes open on in case I find a way to deal with them.
First, my “deaf accent.” I know it exists, even if I can’t hear it. It makes my voice very recognizable and slightly puzzling to folks who at first can’t figure out what accent it is. I’m not ashamed of it and I don’t want to pretend to be somebody I’m not, but I want to be able to recognize, understand, and control it so I can reassure myself that the way I sound won’t get in the way of what I’m saying. Someday, I tell myself, I will go see a speech therapist. Someday when I can afford one.
The habits I’ve picked up that make me look hearing. I do them by reflex and not to deceive, but they’re still vestigial in some way. I’ll laugh when I’m in a crowd that’s laughing even if I don’t get the joke. I purse my lips and pretend to whistle when I’m dancing around the kitchen cooking, although this is absurd since I can neither whistle nor hear whistles. Nodding in agreement to complaints about crying babies, ringing phones, or middle-school flute practices in the next room that I can’t hear. Saying “beep!” at the same time the microwave chimes its “I’m done!” sound, even though I’ve never heard a beep come from a microwave. Funny, the things a kid picks up. They’ve got no apparent purpose other than being what everyone else does.
Finally, I don’t want to force everyone to adapt to my habits, but I don’t want to keep asking my mom, my roommates, my aunt, or random strangers I happen to be next to on the street to tell me what my voicemail messages say. So I’m waiting a week to make sure the decision is sane, but this is what my new voicemail message is going to be.
You’ve reached the phone of Mel Chua. Please do not leave a message after the beep unless you have to, because it’s hard for me to hear them so I may not be able to get back to you. If you could do me a favor instead and text message this number or send an email to voicemail at mel chua dot com, I’ll get back to you right away. Thanks for understanding, and remember - please don’t leave a message after the beep!
Saturday, January 20th, 2007 | Uncategorized | 1 Comment »
I sabotage myself.
It’s a stupid thing to do. It’s pointless and wasteful, like trying to armwrestle yourself; you won’t get far, but you’ll get tired fast. But I overpromise, underdeliver, waffle, baffle, perform well for a few weeks and then completely disappear. I’m undisciplined with time, space, commitment, and focus. I actively stop myself from unleashing my own potential. I make it so that other people think of me as an irresponsible idiot. Worst of all, I do it consciously.
I don’t want to be good.
Well, no. I want to be good. In predictable, standardized, measurable ways. Things that make sense on a resume. Numbers I can point to on a transcript, on a test, on a letter of reference. Unambiguous proof that I fit in and make sense according to their standards. Rest from the incessant demands of having to make my own. I desperately want to fit in that square hole, so I whittle down the round peg until it’s an inscribed shadow of its former self and rattles around loosely in the assigned slot - but damn it, it’s in there, isn’t it?
My soul is screaming as I type the previous paragraph.
I want to be quote-unquote good. I don’t want to be great. I don’t want the reputation, nor the responsibility, nor the solitude of standing at a pinnacle or blazing a new path. If I’m good at something, for the love of God don’t tell me because I will start tearing it down. Bless me with mediocrity. Let me not know, because knowing is hard. Knowing is this terrible, this beautiful monster of potential clawing out through the seams I can’t watch and can’t patch fast enough. It won’t stop, won’t be schooled, won’t be tamed; it just batters opportunity against the door until it splinters, then devours your life. Give me my life. I don’t want to use it. I just want to hold its warmness in my hands and look at what it could be, because dreaming is easy and doing is hard.
I want to be. Not of service in any way.
What if my calling ends up being somewhere I don’t want to go? Hey. Here I am. Send me… to any one of these fifteen pre-approved peer-reviewed destinations. And I expect frequent flyer miles.
And what if I stop holding myself back (because I do)? What if I accepted my lack of focus in an accepted area, grew selfish enough to puruse my own moments of flow, and allowed myself to institute the discipline needed for true creativity, external standards be hanged? If I let myself be whatever I can be, and it turns out that the best I can be isn’t really that great?
We will now take a moment as Mel puts her sane face back on.
This post has been written by a component of Mel that doesn’t often speak or wish to be acknowledged. I don’t want to admit to its existence. It’s not something I’m supposed to be. But dragging it painfully into the sunlight is the only way I’ll ever deal with it. Begone, demon.
Of course I’m gone. I’m right here.
Thursday, January 18th, 2007 | Uncategorized | No Comments »
