Audio geek questions re: volume doubling

[Dave Bryce]

I’m trying to figure out how volume doubling works in decibels.

 

It seems to be commonly held that +3dB doubles power, but it takes +6dB to double perceived volume/loudness (although I’ve also read that it takes +10dB to double perceived volume/loudness as well).

 

First question: do you agree that it’s +6dB?

 

Second question: if +6dB doubles perceived volume/loudness, how much does +12dB raise it? Or +18dB?

 

My inquiring mind wants to know… 🤔

 

dB

 

 

[jazzpiano88]

15 minutes ago, Dave Bryce said:

I’m trying to figure out how volume doubling works in decibels.

 

It seems to be commonly held that +3dB doubles power, but it takes +6dB to double perceived volume/loudness (although I’ve also read that it takes +10dB to double perceived volume/loudness as well).

 

First question: do you agree that it’s +6dB?

 

Second question: if +6dB doubles perceived volume/loudness, how much does +12dB raise it? Or +18dB?

 

My inquiring mind wants to know… 🤔

 

dB

 

 

For sure, 3dB doubles power.  Doubling volume is subjective because it is perceived different by different people. I read that psycho acoustics studies go with 10dB for doubling volume.  It would be nice if there was a definitive relationship between pressure wave intensity at the ear drum and perceived volume.  
 

If that’s the case then 20 dB would double the double, or 4x volume and 30dB would double the double the double, or 8x volume.  
 

I too would like some experts to chime in to agree or correct this.  

[KuruPrionz]

Bearing in mind that scientific analysis of sound waves is profoundly different than human hearing, it is impossible for a system that can accurately measure all frequencies and combinations of said frequencies to predict the huge variations in human hearing (including a wide range of deafness and other afflictions).

As a species, we lack the same consistency that lab equipment possesses. 

If we add the vast array of listening situations to the equation, it's truly impossible to say much beyond "These charts are these charts." 😇

[Finale]

Perception is pointless to analyze, since a 1kHz sinewave is a lot more annoying to hear than a 60 Hz or 12 kHz one of same volume. So go with simple facts.

 

In Wavelab, you can either select % or dB to apply changes in signal amplitude and here are the equivalents :

 

50% = -6 dB

25% = -12 dB

200 % = +6 dB

400 % = +12 dB

[Philbo King]

dBw (power) is different than dBv (voltage).  +3 dB is a doubling of power.  +6 dB is a doubling of voltage. 

 

Perceived volume is not really measurable, at least not until Elon perfects his computer/brain interface.

[PianoMan51]

The measurement Bell (and the decibel dB) was invented by Bell Labs scientists who were studying the physical nature of sound with emphasis on making efficient telephone networks. Back in the 20s when they also invented the amplifier and electric microphone. And then researched vocoders, transistors, microwave background measurements, lasers, and on and on.
 

It was they who explored the logarithmic nature of our hearing. The ‘+10dB equals a doubling of perceived sound volume’ was a convenient averaging of many test subjects. Move from 10dB to 1 Bell (it’s the same) and you realize that the whole measurement scheme was based around human hearing.

[Dave Bryce]

All good info so far….thanks!

 

I’m trying to figure out how to say how much louder +12dB is, even if it’s approximate…

 

…or do y’all think the +3dB power spec is the more relevant spec as far as dB increase?

 

dB

[PianoMan51]

The logarithmic nature of our hearing is always confusing. 
 

We think adding a second powered speaker on stage will double the volume. No, it adds 3dB of volume, which slightly increases volume, but gives us the opportunity to spread the volume over a wider expanse. 
 

I worked in  telecommunications test firm for 20 years. Rather than pull out a calculator, I ended up just using a handful of useful short cuts. 
 

Here’s one…

 

Ten times the power = two times the volume.

Or, +10dB doubles perceived volume.

 

An example is, 

 

If you want to double the volume of 10W amp, you need 100W. (All other things being equal.)

 

 

[Audiofreq]

On 4/17/2024 at 10:22 AM, Dave Bryce said:

All good info so far….thanks!

 

I’m trying to figure out how to say how much louder +12dB is, even if it’s approximate…

 

…or do y’all think the +3dB power spec is the more relevant spec as far as dB increase?

 

dB

The first Bell would double the perceived output on an 'average ear.'
The last two dB would not really be noticed since it takes ~3dB of change for most to perceive a change.
12dB would be louder than 10dB but by exactly how much? Exactly 2dB  

[RABid]

On 4/17/2024 at 12:22 PM, Dave Bryce said:

I’m trying to figure out how to say how much louder +12dB is, even if it’s approximate…

Say it in terms of pure physics. Clarify it with a statement that not all humans perceive volume changes in the same way.

[Dave Bryce]

4 hours ago, RABid said:

Say it in terms of pure physics. Clarify it with a statement that not all humans perceive volume changes in the same way.

 

Not so easy to do in a way that most people can relate to - the physics approach can tend to make the average person’s eyes glaze over. 

 

Lots of discussions/marketing materials rely on the dB spec to express loudness without saying how that translates to real life sonics.  It’s kind of like referring to frequency response on studio monitors without addressing what the cone materials and speaker topology do to the actual sound - 40dB low end frequency response spec does not usually sound the same on a paper woofer as it does on a Kevlar one, and sealed boxes do not sound the same as ported ones.

 

dB

[Delaware Dave]

From what i remember it takes a 10 db increase in power to produce a 3db increase in perceived volume. 30 db in loudness is twice the perceived loudness as 27 db.  Pianoman51's post above FTW ....

 

In order to achieve the 3db increase in loudness it takes 10x the power (given no other variables are changing) to achieve the 3db increase in perceived loudness.

 

 

[Dave Bryce]

7 minutes ago, Delaware Dave said:

From what i remember it takes a 10 db increase in power to produce a 3db increase in perceived volume. 30 db in loudness is twice the perceived loudness as 27 db.  Pianoman51's post above FTW ....

 

In order to achieve the 3db increase in loudness it takes 10x the power (given no other variables are changing) to achieve the 3db increase in perceived loudness.

 

So, you’re agreeing with the POV that 10dB is double audible loudness…which is the spec that makes the most sense to me as well.

 

If so, would +20dB be triple the original volume, or double the +10 dB boost (4x original volume)? Or…?

 

dB

[The Real MC]

From a BTEE degreed engineer who knows audio engineering (me):

 

A doubling of power is a +3dB change.  Power is a dual unit system because it is the product of voltage and current.

A doubling of singular unit such as voltage or audio volume is a +6dB change.

 

dBu, dBV, dBm etc are all scales of dB systems with different reference points and unit scales.  Reference points of 0dB is not the same voltage or volume between scales.  However, changes of (x)dB that double the unit is consistent across the different scales.

 

Yes, the dB system can be confusing.  But before Bell Labs proposed the dB system, it was even more confusing.

 

Another interesting fact: doubling the power of an amplifier results in only a 3dB increase in volume, while doubling the drivers results in a 6dB increase in volume.

[jazzpiano88]

9 hours ago, Dave Bryce said:

9 hours ago, Delaware Dave said:

From what i remember it takes a 10 db increase in power to produce a 3db increase in perceived volume. 30 db in loudness is twice the perceived loudness as 27 db.  Pianoman51's post above FTW ....

 

In order to achieve the 3db increase in loudness it takes 10x the power (given no other variables are changing) to achieve the 3db increase in perceived loudness.

 

So, you’re agreeing with the POV that 10dB is double audible loudness…which is the spec that makes the most sense to me as well.

 

If so, would +20dB be triple the original volume, or double the +10 dB boost (4x original volume)? Or…?

 

Yes!

 

Too many units flying around here.  Don't talk about 3dB increase in loudness!  

 

dB calculations are only mathematically relevant to voltages and power. 

 

Power increase of P2 to P1:      dB = 10 log (P2 / P1)

 

Voltage (intensity) increase from V2 to V1:     dB = 10 log (P2 / P1)  = 10 log ((V2^2 /R ) / V1^2 / R) ) = 20 log (V2 / V1)

 

Loudness:   Empirically 2x Loudness = +10db Power = +20dB Voltage.

 

So to your question:   +20 dB power would be 2x ( 2x ) = 4x loudness   To quote Ed McMahon,  "You Are Correct, Sir".  (with all caveats in mind on perceptive differences and frequency dependent, but total spectral average).