What exactly is louder?

[soggybag]

If I have a signal that swings from +1v to -1v and I feed this into a transistor that outputs a +3v to -3v signal is that louder? What happens when this signal runs past two clipping diodes? It should now be clipped at +0.7v and -0.7v. Is this louder than the input signal? Or does it just sound louder because of the clipping?

What about multiple transistor stages. It seems like the four stages in the BMP get pretty loud. These are common emitter stages, so the maximum gain is only 1/2V+. Could you build a louder BMP using emitter followers?

What makes something louder electronically?

[R.G.]

"Louder" has no meaning for a voltage signal. Louder happens in the human ear. And although it's related to the pressure variations in the air, it is not directly related to those variations. This is why a 100W amp is not ten times as loud as a 10W amp. It is only apparently twice as loud.

If I have a signal that swings from +1v to -1v and I feed this into a transistor that outputs a +3v to -3v signal is that louder?

No. But it is bigger. If you put a 1V peak (which is the same as +1V to -1V or 2V peak-to-peak) signal into an amplifier and a 3V peak signal into the same amplifier, and the amplifier (a) did not overload on either signal internally, and (b) drove a loudspeaker without either the amplifier or speaker being driven outside their linear limits, the 3V peak signal would product a greater loudness to a listener. But not a three-times louder difference.

What happens when this signal runs past two clipping diodes? It should now be clipped at +0.7v and -0.7v. Is this louder than the input signal? Or does it just sound louder because of the clipping?

A 1V peak signal clipped by 0.7V diodes is usually perceived to sound louder by most listeners. But both the peak voltage and the peak sound pressure (air pressure) levels will be smaller. The human ear interprets distorted signals in different ways, and there is a difference in the apparent loudness of equal-sound-pressure sounds depending on frequency. Google "Fletcher-Munson".

What about multiple transistor stages. It seems like the four stages in the BMP get pretty loud.

They do not get loud at all. But they do have a lot of voltage gain.

These are common emitter stages, so the maximum gain is only 1/2V+.

Actually, no; the maximum output voltage is V+ peak to peak, or V+/2 peak. That's not the same as loudness, only voltage level. And voltage level out is not the same as gain, which is a ratio of the output to input.

Could you build a louder BMP using emitter followers?

No. First of all, a BMP has no loudness, only voltage gain and maximum output level. Emitter followers have no voltage gain.

What makes something louder electronically?

Nothing. There is no way to do that. What makes things bigger electrically, which can be translated by a power amplifier and speaker into air pressure waves, which can be interpreted by the human ear as loudness, is voltage gain in most of the circuits normally used.

[Mark Hammer]

RG is absolutely correct.  Amplitude is electronic, but "loudness" is psychoacoustic.  It is a perception, and like any perception, will depend on a variety of characteristics and circumstances.

The relationship between objectively measurable amplitude and perceived loudness is generally (and I mean generally) given by Stevens' Power Law ( http://en.wikipedia.org/wiki/Stevens%27_power_law ), conforming to a general principle that applies to virtually every stimulus you can sense: touch, taste, sound, smell, etc.  The general principle is that the more intense any stimulus is, the more change is required in that stimulus to make it seem more intense.  That's why volume pots are always log.  It is easier for you to taste the difference between 1/4 and 1/2 teaspoon of salt in an 8oz glass of water than it is for you to taste the difference between 1tsp and 2tsp.

But of course, it is one thing to examine and define the amplitude-to-loudness correspondence in the lab under tightly controlled conditions, and another to examine it in the real world where there are other concurrent sounds and distracting stimuli, and perceived intensity is as much a function of what else is going on as the specific sound stimulus in question.

One of the things that determines perceived loudness is attention, and attention-getting properties.  In the same way that crisply focussed images against a blurry surround leap out at us when it comes to vision, clearly defined sounds are heard more (and attended to more) than ill-defined ones.  Insomuch as harmonic content and its proper alignment make a sound more "defined", that's one of the reasons why a decent buffer, and its ability to retain full bandwidth, can make a signal seem louder.  Granted, shaving off treble reduces the overall amplitude in an objective manner, the actual added signal, when full bandwidth is retained,  does not add THAT much more amplitude.  Rather, it is the improved opportunity for us to do the aural equivalent of "focussing" on a sound that helps to make it seem louder.

One might propose that, in evolutionary terms, since few sonic spaces permit high frequency energy to travel very far before it is damped, sounds with more harmonic content grab our attention because we have evolved to "hear" them as closer and more significant.  So, not surprisingly, even if you turn the fuzz volume down a lot, when you switch back and forth between bypass and distortion, the distortion feels louder and more in-your-face.  I would contend there is an evolutionary influence at work there.

At another level, consider that what it takes for you to hear a sound as "louder" when compared against itself with the volume pot turned down a notch, is not the same as what is required for you to hear the sound as "louder" when played against several other concurrent, and loud, sounds.  It might take very little tweaking to think it is much louder, when on its own, but a whole lot more tweaking the volume/gain to hear it as louder when it is competing for your attention with other sounds.

If there IS a correspondence between objective signal qualities and perceived loudness, I would say it is that when any two identical-amplitude signals are compared, the one with greater harmonic energy, and especially more sustained harmonic energy (i.e., it doesn't die out right away) will be heard as louder.

[MikeH]

If a tree falls in the woods and no one is there with a dB meter, is it loud?

[Mark Hammer]

No, but the tone is.....amazing.

[kungpow79]

11.  Its one louder. 
http://www.youtube.com/watch?v=EbVKWCpNFhY

[petemoore]

  The word is so messed up, we should discover a new one for what "Loud" means:
  "quiet, but ugly" [a quiet band with say..cheep speakers].
  "A type of guitar sound" [we'll try distorted for this one].
  "A high shrill voice" [slightly off-pitch helps].
  The ears of the person saying it's too loud experiencing a treble tone that bothers their ears to an amazing degree [but no-one elses].
  A word used to express pretty much anything involved with sound which is percieved to require a bad review.
  Enough with the mis-definitions [you want more? I got 'em...].
  I don't think I'm throwing garbage in the pot already filled with plenty of ingredients that make one complex stew, describing how a clipped signal of lower average power can sound louder [technical definition: bigger-volume, sorry best I can muster for a technical definition of 'loud':
 First word "Accelleration/de-accelleration" [ok, two words].
 with a smoother wave, the accellerations and deaccelerations of the speaker and ear and the related pressure levels rise and fall more steadily.
 Once clipped by diodes, as the pressure rises evenly [as the wave moves from 'middle point' upward] until it voltage level reaches the diode threshold, at which point the upward rise in pressure is leveled...this equates to the speaker cone drive toward foreward excursion is very suddenly halted as voltage stays at that threshold, cause a spike in pressure at the coil to cone, this wave-bump travels through the air and the quick de-accelleration is percieved as 'louder' because there's a higher peak amplitude associated with the sudden pressure change.
 The average 'power' is less, consider the tops and bottoms of the wave are chopped off.
 

[CynicalMan]

For a constant waveform, the acoustic loudness is best measured by root mean square.
So, here's a decent measure of loudness for a continuous function (or waveform) f(t) (in volts) defined over the interval T1 ≤ t ≤ T2 in decibels relative to 1Vrms:


Good luck 

[StephenGiles]

  The word is so messed up, we should discover a new one for what "Loud" means:
  "quiet, but ugly" [a quiet band with say..cheep speakers].
  "A type of guitar sound" [we'll try distorted for this one].
  "A high shrill voice" [slightly off-pitch helps].
  The ears of the person saying it's too loud experiencing a treble tone that bothers their ears to an amazing degree [but no-one elses].
  A word used to express pretty much anything involved with sound which is percieved to require a bad review.
  Enough with the mis-definitions [you want more? I got 'em...].
  I don't think I'm throwing garbage in the pot already filled with plenty of ingredients that make one complex stew, describing how a clipped signal of lower average power can sound louder [technical definition: bigger-volume, sorry best I can muster for a technical definition of 'loud':
  First word "Accelleration/de-accelleration" [ok, two words].
  with a smoother wave, the accellerations and deaccelerations of the speaker and ear and the related pressure levels rise and fall more steadily.
  Once clipped by diodes, as the pressure rises evenly [as the wave moves from 'middle point' upward] until it voltage level reaches the diode threshold, at which point the upward rise in pressure is leveled...this equates to the speaker cone drive toward foreward excursion is very suddenly halted as voltage stays at that threshold, cause a spike in pressure at the coil to cone, this wave-bump travels through the air and the quick de-accelleration is percieved as 'louder' because there's a higher peak amplitude associated with the sudden pressure change.
  The average 'power' is less, consider the tops and bottoms of the wave are chopped off.
 

I always remember a request from a musician on stage at a gig when he asked for his monitor to be turned down to "deafening"!

[Nasse]

I was at concert and the band played too loud, above treshold of pain. Me and many more complained about it to the band, so did those who had paid for the band and hired it there. They just ignored and kept playing loud as hell. Since then I never have bought records of that band or any bandmembers, because I think they are assholes

[Mark Hammer]

Then there is that phenomenon I am all too fond of reminding people about: the wavelength of very low frequencies and the relationship between loudness and distance.  IN the case of ultra-low stuff the relationship is opposite to what you'd think - it sounds louder the farther away you are.

[petemoore]

  Whew OT...but since it's rant time:
  Buy it and try it...no need to understand it, that'd only give it a chance to work 'right'. There is no right...only plenty of compromises and some definitive 'wrongs':
  4 open back guitars amps in a corner with a glasswall.
  2 of those guitars L/R handed strats forming an X cross.
  1 of the guitarists/amps making a 100% intelligible noise that the other 3amps effectively destroy so that all are brought to very near 0% intelligibity.
  ...thats' just the guitars, the ''simple'' part...
  Every week, same 4 geetar-guys at jammnight...lol, nice amp, too bad it has a nice amp right next to, and another adjacent to it, to cancel everything out.

[Gordo]

Since then I never have bought records of that band or any bandmembers, because I think they are assholes

Hmmm, now I'm worried.  Most bands just aren't loud enough anymore.  Is it the years I spent in front of my Marshalls every night?  Or am I an asshole?  My wife is always telling me I'm full of crap...now it's all starting to make sense...

[Nasse]

It was more than 25 years ago when it did happen, I had long hair and had Marshall with big cabinets then  and was used to play loud and our practice room was small and I standed next t crash cymbal, so I don´t complain for little inconvenience. I´m used to construction work with lots of noise tools and in the army I learned how tho use TNT and many more

I only wanted to tell that I just think that this too loud band´s attitude then was very very bad and stupid. We just asked them drop the volume just a bit so that everybody´s ears stop hurting all the time and for every note in every part of the concert room. In deed I like to hear a rock band loud, but not that loud, 130 dB is too much imho

But it was me again giving off topic comments, perhaps the original question was something else, interesting question and many good answers

quote "My wife is always telling me I'm full of..." Obviously she loves you very much, my wife does the same