Audio, hi-fi and car audio - New page on room acoustics, amplifier power, etc

In article 49df07a7.66175234@localhost, Don Pearce
wrote:
On Mon, 06 Apr 2009 18:17:32 +0100, Jim Lesurf
wrote:

Interesting article - do you think this will extrapolate to the
ultimate small room, a set of headphones? What I'm thinking about is
the interaction between what you hear and what you see. I mean, if
you are listening with headphones in large or small rooms, do your
acoustic perceptions of what you hear change as a result?

That is a somewhat different issue since - if I understand you
correctly - you are meaning being affected by what you *see*. The
analysis I did was to assess the effects in terms of perceived volume
depending on a short-term integration in human hearing, and the time
domain profile of the 'echos' in domestic rooms.

In effect I'd expect *all* 'echos' inside headphones to fall within the
integration time. Also, for in-ear or closed back the behaviour becomes
a pressure variation determined by the volume being changed by the
'speaker' movements. But this strikes me as totally different topic to
the one I considered.

Not entirely different, because this is after all about perception, and
this is a factor in that perception.

There are very many factors that affect perception. I dealt with just one
of them on an 'all else being equal' basis. That's the normal method for
explaining how one effect can produce a change. I may look at others in the
future - but you'd be welcome to do so if you prefer. :-)

I do intend assessing the effects of variying room acoustic behaviours and
loudspeaker directivities at some point. But no idea at present when the
supply of round tuits will permit this. Recently they have all been used
for production in other topics.

It is, if you like, an uncontrolled (uncontrollable) variable in your
thesis.

Not really "my thesis". My article is based on work by various other people
who have done the experiments, etc. There are indeed many other variables.
cf above.

FWIW even in basic texts like Howard and Angus you will see the explanation
that human hearing integrates over the order of 30ms to get a perception of
peak loudness of brief events. So I can't say I regard what I wrote as more
than putting two and two together and explaining the implication to
readers.

I carefully avoided more complex questions like how the perceived peak/mean
sound level might vary with acoustic, etc. Or what the late lamented John
Crabbe called a 'claustrophobic' effect for loud sounds in a small room,
presumably caused by being surrounded by multiple short-term echos. Maybe
some other time... ;-)

My main interest was to caution people who might have been lead by what
they read elsewhere into thinking they had to buy kW amps to get
'realistic' levels in typical UK domestic rooms. That may be so for
instananeous transients. But probably not in terms of the perceived levels.

Yes. I think you can expect the sensitivity, etc, of hearing to change
with time of day and many other factors. But as above I wasn't
considering that. Just what change in amp power you might need for a
change of room size when all else was equal.

OK, I see that. How much of your conclusion do you think is inductive,
and how much deductive?

As above. I am simply putting together what others have found about the
effective integration time of human hearing and the effect they report it
having on prerceived loudness with the way the time domain pattern of a
simple room varies with room scale size. No idea how you'd rate than in
terms of saying it was either of the terms you use.

So I think this probably has a great deal further to go than the
simple acoustic interaction of room size and the formation of
resonance.

Agreed. But I didn't attempt to do all things for one 3-4 page article.
No doubt these are topics for future articles... :-)

Time they gave you a whole issue, then!

Tell the editor. :-)

TBH I doubt I could fill an issue unless I spent *well* over six months
working for it. The max I've managed was 10 HFN items in a year, some of
which were just a couple of pages. Although I do also produce about 2 pages
per month for another (non audio) mag as it is another interest I have.

Afraid my workrate is generally up to about 4-6 HFN items per year that
require any significant analysis, etc. Too busy with the 'real world' the
rest of the time, and I am slower now than when I was young. ;-

And I don't really have any interest in writing 'subjective opinions'. They
are much easier to write as you just sit down and type. On that basis I
could probably do ten times as much! But there are more than enough people
doing that already for my taste. Happy to leave that to them and do items
that require me to think a bit and do some analysis, measurement,
investigation, etc.

Slainte,

Jim

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