I have read about a distinction between loudness and volume for sound.
Is there a real difference? What is it?

Hi fred211,

Yes, there is a difference. In laymans terms, using a stereo as an
example, if you want to listen at a low volume, sometimes certain
frequencies need to be boosted (made more audible) in order for the
music to sound "full." Imagine the LOUDNESS button on a stereo. It
makes the sound full without increasing the volume. It may sound
louder, but in reality, certain frequencies have only been made more
audible. You get a sensation of more loudness because the sound is
fuller, but in reality, it is the same volume.

Here's the long version of this concept:

Fundamentals of Audition
http://psych.hanover.edu/classes/sensation/chapters/Chapter%2010.doc

Here's the same link with these words highlighted so you can scroll to
relevant parts:

loud perception volume sensation 
http://64.233.187.104/search?q=cache:TbihXKdVzxgJ:psych.hanover.edu/classes/sensation/chapters/Chapter%252010.doc+loud+perception+volume+sensation&hl=en

If this is unclear to you, or if you would like a different link,
please ask via the "request for clarification" feature.


~~Cynthia


Search terms used at Google:
loud perception volume sensation

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Request for Answer Clarification by fred211-ga on 14 Jun 2005 11:10 PDT

This is not clear - certainly explaining the distinction between
"loudness" and "volume" by reference to the knobs on stereos  marked
"loudness" and "volume" is hardly helpful, nor is the unexplained term
"full" very helpful; moreover saying increasing the  loudness makes
the sound "more audible" does  not really make this clear to me. The
link is not particularly helpful to the layman, albeit one with a Ph.D
from Oxford in the philosophy of science!. The volume of the sound is
correlated with the square of the amplitude of the sound wave -what is
the loudness correlated with? I guess certain frequencies affect the
ear diffedrently and their volume is not correlated to subjective
responses to sound in the same way, but if this is the relevant
information, it needs to be explained clearly and in detail.

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Clarification of Answer by cynthia-ga on 19 Jun 2005 01:34 PDT

fred211,

So sorry you copuldn't wait for my reply. I work full time away from
Google, and my personal life has been very busy this past week.

I'm glad you were able to get a better explanation from a Commenter. I
would have continued my search for an online explanation for you, to
your satisfaction, had you waited, --regardless of the price.

You can tell if a researcher is "ignoring" you by entering their user
name into the Google Answers search area. Had you entered mine, you'd
see I was not here for 4 or 5 days.

Rating and closing a question very soon after a clarification request
doesn't give Researchers time to respond to you! Most researchers work
at other jobs and do this part time.  You can read the FAQ's and Help
& Tips links, on the bottom of every page to find out more about how
the service works.

~~Cynthia

Answer was poor and suggested request for clarification produced no
response. A (free) comment produced a more understandable explanation,
though my understanding is not free of confusions: assumming loudness
"boosts" certain frequencies, say high and low (as my son's physics
professor has suggested), does this not mean that the volume (sorry,
intensity) of these frequencies is also increased ? Would not the
total intensity or voulme of the  over-all sound be greater in this
case; perhaps this is why the two concepts  of loudness and
volume/intensity are easily confused.

I agree that this Answer is weak, but then, what were you expecting for 2 bucks?

Here is my opinion on the matter, from a physics perspective.  For the
purposes of a scientific discussion, I do not like the word 'volume'. 
It doesn't have a clear definition.  You claim it is proportional to
the square of the amplitude of the wave, but I think a better word to
use would be intensity, which power per unit area.  That has
unambiguous units, say watts per square meter.  Volume doesn't clearly
have units associated with it (well, liters is a unit of volume, but
you know what I mean...).  Intensity is definitely proportional to
amplitude squared, no need to squabble about definitions.  Loudness
doesn't have any clear units either, but you can't get around that by
just switching words, because loudness is a psychological quantity,
not a physical one.  I think it is pretty clear that loudness depends
on human perception.  A sound cannot be loud if you can't hear it, so
a sound with a frequency below the lower threshold of human hearing
(or above the top one) is less loud than one that can be heard, even
if it has a greater intensity.  So the question of the difference
between intensity and loudness basically boils down to: how does the
sensitivity of the human ear vary with frequency?  Probably not all
human ears are exactly the same in this respect, so likely there is no
precise answer to this question.  However, I have seen it written many
times that the peak sensitivity is around 1000 Hertz (that's near the
B above the C above middle C).  So a monochromatic sound of a given
intensity sounds loudest if its frequency is around 1000 Hz, quieter
both above and below that frequency.

Searching for "psychoacoustics" will give you a lot of information on
the definition and measurement of loudness.

Ian G.