Just because the author is ignorant of the context doesn’t mean that the engineers working in those fields are. They use it because it all makes sense in context.

Sure, but the author is wrong.

“How old is your son?” “He’s 3.”

Clear in context. People write things like dB SPL (A-weighted) in spec sheets because spec sheets benefit from being unambiguous. Most of the time it’s really clear, like you’re talking about insertion loss or amplifier gain and there’s only one reasonable way to interpret it.

I mean it's always a little bizarre when the default unit used to measure something is dimensionless. Why not set a default (like STP) that's assumed to be the baseline unless otherwise specified? It would be like if Celsius had no reference point and every time you said water boils at 100 degrees Celsius people came out of the word work to smugly correct you "Only if you first say 0 degrees C is when water freezes, which you can't assume. What if 0C is actually absolute 0?"

Many scientific measurements are entirely contextual. e.g. What is 0 V? Ground? Is ground across the globe always at the same potential? Nope. What's ground on a space station? Ground potential is whatever we want it to be. You don't need to define what ground potential is in, say, a computer, relative to some global standard for things to work.

How about velocity? What's 0 m/s? What does it mean to be absolutely still? All motion is relative, and being still is entirely a matter of perspective. You might be sitting still on a train, but traveling very quickly relative to a cow standing still while you blow by.

Bels are a relative measure that confuse some because they pop up in different contexts that seem unrelated. However, they are useful when dealing with quantities for which most pertinent relationships are exponential. e.g. They work for sound because humans perceive exponential increases in volume in a linear fashion. Something that is 3dB louder is twice as loud in terms of pressure levels, but we only perceive it as a little bit louder. Sound pressure levels are both relative measures and an attempt to reflect human perception . That makes them, necessarily, a bit odd.

It's a power ratio. 1dB always means a power ratio of 1.26. That might mean a voltage or current ratio, say, of 1.12, but that is because the relationship between voltage ratios and power ratios is a simple square.

I have a feeling that a lot of people here haven't read the article. There's lots of "Its just a dimensionless ratio" comments

This sounds more like a problem with the 'real' world then.

In the "real world", techically competent people understand decibels just fine.

But this is not arcane knowledge only known by a priesthood. Since you are clearly confused about what a decibel is and how and why it is used, you can read

https://en.wikipedia.org/wiki/Decibel

and all will be revealed.

Can I get 3 M&Ms? Obviously I mean 3 serving sizes, how else would you measure M&Ms?

And before doing any of that, get it tattooed onto your own forearm.

If you want 0 = no sound, then you can’t use a logarithmic scale. You end up with sound being measured as Pascals in the micro to unit range.

“0 dB SPL” is 20 micro pascals which is roughly the threshold of hearing. A loud rock concert at 120 dB SPL is 20 pascals (no micro). The dB figures are a lot more convenient to work with.

It’s intuitive for 0 to be silent and 100 to be full, but if you work with audio you learn that dB are more convenient. Long-term convenience for experts tends to win out over short-term intuition for non-experts. This is why musicians continue to use sheet music and all of its seemingly ridiculous conventions—and likewise, decibels only seem ridiculous to people who don’t work in audio.

I don’t know what more usable alternative there would be, to decibels.

> volume sliders start at 0 dB and then go down to negative $MUCHO, until complete silence at -Infinity. And then this same unit is also used to measure how loud my coffee machine is.

They're not the same unit, at all.

The audio software is a skeuomorphism from an analogue mixing console that is applying a change to a signal. 0 is unity gain and deviation from this describes an amplitude variation. This is important, as it means you are either discarding information by lowering the level and reducing dynamic range, or interpolating new information (/ decreasing SNR) by applying gain. This is less important today with floating point, but has strong historical reasons for existence across both analogue and digital domains.

If you look at an audio power amp, you will likely have some form of positive number as this is applying gain. Depending on the context this may have some specific meaning or it may be a screen print of a Spinal Tap logo and the numbers 1..11. These are all just UI decisions and part of doing that well is presenting coherent information for the target user group.

When you're talking about an acoustic noise source this is dB SPL which is a quantifier against a physical reference. That reference level quantifier is omitted a lot, which leads us to a lot of the angst in this post and the comments here. These are precise measurements, with very specific meaning. Their expression is often sloppy, but the units aren't to blame.

(excuse me while I got "full HN" here - I appreciate the irony in this response noting your first few sentences)

The reason people respond strongly to comments like this (or those about Git, or Rust) is because details matter. When you immerse in a domain, you learn the reason for those details. That does not mean things can't be improved, but this also does not imply those details can be removed or are wrong. A lot of the world, particularly when working outside of the bounds of a computer, depends on necessary complexity.

> As an example, it makes no sense to me that eg in audio software, volume sliders start at 0 dB and then go down to negative $MUCHO, until complete silence at -Infinity.

This one doesn’t bother me. Those sliders, and especially the real analog sliders they’re modeled after, don’t have an absolute scale — they are attenuators that reduce voltage. So 0dB is the same as no slider at all, -20dB reduces voltage by a factor of 10, etc.

Ok, I bite. Please come up with a mapping of 0 to 100 to -inf dB to 0 dB attenuation.

And then put two in series. Is there a simple formula to calculate the total attenuation?

This works flawlessly with dB. Just add. And it doesn't matter how you break it: -20dB and -20 dB in series is the same as -40dB and 0dB.

It makes perfect sense that the sliders start at 0dB and go down to -inf. Maybe you don't understand it, but it definitely makes sense. Everyone who uses dB has also tried a % scale with 100% as 0dB, and then later made a conscious choice to figure out how dB work.

Maybe they're all in a conspiracy to make things needlessly complex. But that's not the only possibility.

There is no such thing as full volume, and there is not such thing as zero volume.

dB is always relative, even when it appears to be an absolute unit. The 0 dB marking at the top of the volume slider on pro audio gear (more likely +3 or +6 or something similar to leave some headroom) means "0 dB relative to the maximum rated power level." In pro gear this will be an absolute industry standard of some sort, likely one where the load impedance is also defined. 1 milliwatt into 600 ohms or something like that. The distinction between voltage and power is always going to confuse people, but that's not the dB's fault.

A major reason decibels are used is to make it easy to assess the overall gain or loss of an entire chain of processing stages: you simply add the numbers. The equipment's output can only go down from 0 dB, so the rest of the scale is negative.

As for sound pressure levels in dB, those are given relative to a 0-dB point that corresponded originally to the faintest sound people were generally considered capable of perceiving. These days "0 dB" refers to a specific amount of acoustic power, which I don't know off the top of my head, and that might or might not be near the threshold of perception for a given listener. But the reasoning still applies: amplification or attenuation of power levels is a simple matter of addition when expressed in dB. Arbitrarily defining a system's reference level to be 100 dB instead of 0 dB would be of no use to anyone.

"I was doing 70 down the highway" is absolutely the sort of thing people say. From context (this conversation takes place in the US, most highways have a speed limit somewhere around 60-70mph) people understand that you are talking about miles per hour.

KSP measures funds in some unitless value, it drives me nuts. Everything else is almost (but not quite) perfect.

Maybe you can say "6 dbm/s"