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The scientific “unit” we call the decibel

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Re: The scientific “unit” we call the decibel

#251

Post by klodolph »

skrebbel wrote: post #207
lambdaone wrote: post #187

It's a bit like hating numbers, and saying "What do you mean by 'three'; what is it - three volts, three amps, three metres? Clearly 'three' is meaningless, and we should stop using it and all the other numbers besides." decibels are simply a dimensionless ratio, used as a multiplier for some known value of some known quantity. In every context where decibels are used, either the unit they qualify is explicitly speci…

To be frank, your comment just reads to me as a "stockholm syndrome" type reaction to a needlessly complex unit that you're intimately familiar with. You see the same in HN threads where people complain that eg Git or Rust are needlessly complex, there's a swath of people who are so emotionally invested in how well they understand the ins and outs of Git resp Rust that any suggestion that maybe things could be better…

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.

Re: The scientific “unit” we call the decibel

#252

Post by lxgr »

lambdaone wrote: post #187

It's a bit like hating numbers, and saying "What do you mean by 'three'; what is it - three volts, three amps, three metres? Clearly 'three' is meaningless, and we should stop using it and all the other numbers besides." decibels are simply a dimensionless ratio, used as a multiplier for some known value of some known quantity. In every context where decibels are used, either the unit they qualify is explicitly speci…

> It's a bit like hating numbers, and saying "What do you mean by 'three'; what is it - three volts, three amps, three metres?

No, it’s a bit like saying “for chocolate M&Ms, 3 obviously means 9, to compensate for the fact that they’re much smaller than the peanut ones”.

Re: The scientific “unit” we call the decibel

#253

Post by sgarland »

rusk wrote: post #84
svara wrote: post #62

Earlier quoted context omitted.

> makes me really doubt that the OP has any practical experience about the things they're talking about. Maybe not, but you can get used to many odd things given enough experience. I totally share the authors view. I don't usually have trouble grasping the definition of a unit, but dBs are just hilariously overloaded. The same symbol can literally mean one of two dimensionless numbers, or one of who knows how many ph…

dB for sound in particular aligns with human experience. The (10 -) 1-10 on a volume knob typically aligns with a logarithmic scale because we hear differences in loudness at an order of magnitude. A linear volume knob would be frustratingly useless as you would have to crank it many many many times the higher up you want to go. Presumably hundreds of times. A traditional pot couldn’t do that of course but maybe you…

Sure, but a. IME, volume controls with 1-10 are nowhere near log b. many manufacturers don’t even do this. A lot of car manufacturers seem to use 0-40 for the stereo volume, which seems completely arbitrary. I’m assuming they decided that’s a good balance between granularity and annoyance, but c’mon… couldn’t have at least capped it at 50? Halfway to 100 feels vaguely more intuitive.

This also doesn’t even begin to touch on frequency response curves.

Re: The scientific “unit” we call the decibel

#254

Post by lxgr »

hgomersall wrote: post #201
weinzierl wrote: post #193

Earlier quoted context omitted.

"decibels are simply a dimensionless ratio, used as a multiplier for some known value of some known quantity." Except they are not. 1 dB can sometimes mean a ratio of ~ 1.26 and other times it can mean a ratio of ~ 1.12. "In every context where decibels are used, either the unit they qualify is explicitly specified, or the unit is implicity known from the context." Maybe in university, but certainly not in the real w…

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.

That’s maybe what it “is”, but not the only thing people use it for in many fields. Very often, it’s a ratio between a measured quantity and some (implied) base unit of the same quantity.

Re: The scientific “unit” we call the decibel

#255

Post by RichardLake »

klodolph wrote: post #234
sanderjd wrote: post #200

Earlier quoted context omitted.

> In every context where decibels are used, either the unit they qualify is explicitly specified, or the unit is implicity known from the context. The author's whole point is that this is not true. To adapt your analogy, it's not like being mad at the number three, it's like being mad about people not attaching any units to the number three, arguing that it's clear in context. It isn't!

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.

That depends, the dropped unit could be either a year or a month.

Re: The scientific “unit” we call the decibel

#256

Post by arghwhat »

hgomersall wrote: post #201
weinzierl wrote: post #193

Earlier quoted context omitted.

"decibels are simply a dimensionless ratio, used as a multiplier for some known value of some known quantity." Except they are not. 1 dB can sometimes mean a ratio of ~ 1.26 and other times it can mean a ratio of ~ 1.12. "In every context where decibels are used, either the unit they qualify is explicitly specified, or the unit is implicity known from the context." Maybe in university, but certainly not in the real w…

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.

The problem isn't really the ratio, but the use in arbitrary contexts that require a lot of pre-existing knowledge. The reference value is sometimes a rather arbitrary value in an arbitrary unit, neither of which is communicated by the "dB" unit suffix.

The SI way to write `10 dBm` is to write `10 dB (1mW)`, clearly communicating both the power level and the reference point and unit. This ensures that you do not have to just memorize a bunch of decibell suffixes and their magical reference values.

Re: The scientific “unit” we call the decibel

#257

Post by lxgr »

hgomersall wrote: post #249
weinzierl wrote: post #240

Earlier quoted context omitted.

I understand that and it just reinforces my point. What 1 dB essentially means is highly dependent on a most of the time silent context.

No, it always means a power ratio. That sometimes can imply something else, but that's on you to work that out.

Yes, but that, i.e. putting the burden of disambiguating some meaning from context on the receiver instead of the sender, is just bad communication.

Re: The scientific “unit” we call the decibel

#258

Post by viraptor »

nyeah wrote: post #239
skrebbel wrote: post #207

Earlier quoted context omitted.

To be frank, your comment just reads to me as a "stockholm syndrome" type reaction to a needlessly complex unit that you're intimately familiar with. You see the same in HN threads where people complain that eg Git or Rust are needlessly complex, there's a swath of people who are so emotionally invested in how well they understand the ins and outs of Git resp Rust that any suggestion that maybe things could be better…

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.

> and then later made a conscious choice to figure out how dB work.

You're just projecting your ideas here. I've not made that choice, it's just the only option in a lot of software - I'd like my % slider back.

Re: The scientific “unit” we call the decibel

#259

Post by GuB-42 »

rusk wrote: post #218
detourdog wrote: post #162

Earlier quoted context omitted.

Nothing to do with decibels but the thermostat on the water heater might be set too high. If one lowers the overall temperature the ratio of cold to hot will balance.

You are bounded by a minimum floor for the hot water. Below a certain point you can get legionnaires. To me it seems like one of two things: external pressure between hot and cold is mismatched so a small change to one side overwhelms the weaker flow. Alternatively it might just be a broken or poor quality mixer that isn’t providing the appropriate ‘nuance’ of control, and that may indeed be expressed as some sort of…

> Below a certain point you can get legionnaires.

I know you mean legionnaires' disease, but the idea of a bunch of soldiers getting to your house because you turned your boiler too low made me chuckle. Good thing the US have the third amendment to protect against this.

Re: The scientific “unit” we call the decibel

#260

Post by nyeah »

viraptor wrote: post #258
nyeah wrote: post #239

Earlier quoted context omitted.

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.

> and then later made a conscious choice to figure out how dB work. You're just projecting your ideas here. I've not made that choice, it's just the only option in a lot of software - I'd like my % slider back.

Right. Decibels are my idea.
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