The Missing Fundamental | Hacker News Reader

The Missing Fundamental

hatsunearu.github.io

66 pointshatsunearu13 comments

Hey, this is my first blog post--I got motivated to write one because of all the cool stuff I find on HN.

I wanted to write a single blog post on bass boost (as mentioned at the end), but I wanted some early feedback on my writing so I split the original blog idea into two.

Obvious points for improvement are the code (playing more than N seconds, etc) and writing some CSS for it, but I'm looking for some readability issues in writing if there are any.

Thanks for reading!

Well, it was an awesome blog post. I have actually lost sleep pondering how itty bitty iems manage to have bass response. Thanks.

IEMs can have pretty good bass response just because they don't need to generate much volume. Hold them about an inch from your ear and turn the volume up high enough to hear from that distance. Very little base at that point.

It's not just the low volume - it's the airtight seal. A very low frequency sound wave is a slow sequence of low- and high-pressures. With an airtight seal, it's much easier to sustain pressure differences from 1 atmosphere from a long time. With no seal, the high or low pressure leaks away from the region near the ear.

This is also why open-ear headphones tend to have lower bass response than closed-ear headphones. For example, compare these frequency response curves:

http://graphs.headphone.com/index.php?graphID%5B0%5D=853&gra...

The open-ear Sennheiser HD650 has around 10-12 db lower bass response than the closed-ear Fostex.

Even more dramatic, look at the dynamic response to a 50hz square wave - the Sennheiser's amplitude drops completely to zero before the next jump of the square wave, while the Fostex manages to maintain about 1/3 of the original air pressure in the headphone cup by the end.

http://graphs.headphone.com/index.php?graphID%5B0%5D=853&gra...

id suggest you find an example where a familiar melody is played using only overtones. that really hammers home the idea that your brain fills in the fundamental.

Nice! Might be helpful to label the harmonics in the sliders.

Excellent post!

Maybe my headphones aren't too good (airpods), but when I remove the fundamental I hear octaves, thirds, and fifths of the fundamental as chords instead. I also have a bit of musical training as well, so that might be helping me distinguish.

EDIT: If I turn the last four sliders all the way up (5-1-3-5), I can barely? hear the tone of the root below the first 5 (the second slider). I can't hear any tones of the very first slider, possibly because there aren't any tones between that and the jump to the next octave.

Maybe I don't understand exactly what I'm supposed to be listening for, or maybe my ears are bad, but I don't think I can hear the missing fundamental unless it's actually being played.

I also don't quite follow how arbitrary harmonics can result in a specific note--is the idea that if you conjoin any 2 or more harmonics of Note X, their pitch will sound like the pitch of Note X even though it is not technically being played?

I have a device that does this (among other things). It's a discontinued product called the Boomcloud Boomstick. It really does make mediocre headphones sound like they produce deep bass.

There have been other similar devices, particularly the SRS Wow! Thing is still popular among musicians, and commands high prices on eBay.

I bought the Boomstick for a DIY BT speaker project, that I had to put on hold. I may pull myself together and actually finish it now :-)

> It is as if the brain knows that the harmonics are related to the fundamental in integer multiples, and calculates the fundamental all subconsciously.

Isn't this fundamentally (no pun intended) how overtones work?

Overtones are another name for harmonics. The only thing that's different is the naming scheme: the first overtone is the second harmonic, and the Nth overtone is the N+1th harmonic.

I like the writing a lot, perfect balance for people without musical training (and an interest for sound). Well done!

Side note: the JS to play sounds throws an error in Safari TP, works fine in FF.

This is really cool!

I was able to hear the fundamental with its slider turned all the way down and the harmonics up using decent in-ear headphones

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