5 ms·
Read for content. I wasn't talking measuring 0-60 time in cars. I was talking about measuring steady 60mph. No one does that, because it's useless (although it
by beat 9y ago
Read for content.
I wasn't talking measuring 0-60 time in cars. I was talking about measuring steady 60mph. No one does that, because it's useless (although it would be easy to measure). 0-60 time would correlate somewhat to impulse response in audio, which is a useful measurement, and much more rarely seen.
I'm reminded of an experimental example a professor showed us in my college audio recording class. He hooked a square wave generator up to both analog tape and digital recorders, and recorded the square wave. Then he played back both sources on an oscilloscope. The tape had a sharp lead spike followed by a shrinkage on the tail of the square, from compression. The digital recording had a rippled top, from frequency-related distortion. Both were inaccurate, but they were inaccurate in very different ways.
- mrob 9y agoInaccuracies visible on an oscilloscope might not be audible to humans. Try applying a 10Hz high-pass filter to some music and comparing the waveforms. There's obvious visible changes but it sounds identical.
- beat 9y agoTrue. And it certainly doesn't explain "better" or "worse". But it explains why music recorded on tape sounds different from music recorded digitally. And it puts a torch to the claims that digital is somehow "accurate", and all we like about analog is just evil bad naughty distortion.
- astrange 9y agoSquare waves are impossible to reproduce because they have infinite numbers of frequencies, but you don't listen to square waves. You listen to music with all its content below 20KHz and anything above that doesn't matter. The only non-ideal thing about music is that it's not band-limited because time matters - that's why compressing music with a lot of cymbals etc smears it across time.
- jjgreen 9y agoMore simply, square waves are impossible to reproduce since they would require infinite velocities
- evilDagmar 9y agoWhat, you don't like it when your speakers cones blow a hole through the wall and possibly the neighbor's roof on their way to Saturn?
- aidenn0 9y agoThis is why you low-pass audio before quantizing. If you put the square-wave through a low-pass filter before recording it digital and on high-quality tape, the digital recording will be more accurate than the tape.
- beat 9y agoThis was a digital recording onto a professional digital system. It was put through a Nyquist filter. Then again, is "accurate" in some mathematical sense the right term? Which one sounds more like music? Among audio professionals, there's a broad consensus that tape sounds better - enough so that there is a strong market for digital plug-ins that emulate the (mis)behavior of tape.
- aidenn0 9y agoIf a pure-digital master can emulate tape, then isn't it superior to tape? (I know that many analog systems have soft-rolloff allowing you more leeway in setting your headroom, but modern ADCs have so much dynamic range that it's a poor operator who doesn't allocate themselves sufficient headroom).
- semi-extrinsic 9y agoYou can't accurately reproduce a square wave by using a Fourier series even mathematically in the infinitely wide frequency response limit, ignoring all physics: https://en.wikipedia.org/wiki/Gibbs_phenomenon https://en.wikipedia.org/wiki/Gibbs_phenomenon
- apenwarr 9y agoWhy are we talking about Fourier series? Uncompressed digital audio doesn't need them, it just records the raw voltage level samples. You still can't produce a perfect square wave, but there's no reason you shouldn't be able to reproduce whatever wave was provided as input (which by definition was produced by something), other than hardware limitations of the playback system.
- wl 9y ago> Why are we talking about Fourier series? Because all real systems are bandlimited.
- krastanov 9y agoYou are quite wrong about that statement. As the other comment mentioned, both analog and digital systems are bandwidth limited and can not reproduce infinite slopes like in a square wave. Fourier expansions are one of the easier ways to study bandwidth, even if there are other formalisms.
- apenwarr 9y agoBut that's the analog system which is band limited, not the digital! The problem is poor analog components after the digital decode phase in this case. A time domain digital representation absolutely can represent a perfect square wave. (There are other waves it can't represent.) That's completely different from a digital encoding that causes ringing in the square wave.
- cnvogel 9y ago
- stcredzero 9y agoI was talking about measuring steady 60mph. Actually, this is kind of a thing: speed measurement and reliability for cruise control. We can get close enough to be useful and quite comfortable. However, most cars don't directly measure their own speed anymore. Instead, it's inferred from other measurements.
- twhb 9y agoI realize you weren't talking about 0-60 time, it was an analogy I introduced. Not meant to be technically similar, only a similar fraction of the whole. I think "driv[ing] in a straight line at 60mph" is a smaller fraction of car performance than frequency response of headphone performance, and 0-60 time more similar.