All,
I’m considering buying a small bore D chanter to make my incessant practicing a bit more bearable for my spouse (she’s a good sport and very supportive, but everyones got limits). My question is, are the small bore chanters really that much quieter?
In a word, no. They’re different. Somewhat easier to reed, and they have smaller toneholes. They’re different to play, but not a whole lot quieter.
Lower pitch narrow chanters can be quieter than D, but the one narrow D I’ve had (Rogge) was only slightly quieter than a wide-body D.
Stuart
I did hear one of those Rogge narrow Ds this past summer and have to say I was impressed. It was louder than I expected but very nice-sounding, better than most wide Ds. Of course, Noel Carberry was playing it, so I’m sure he had a lot to do with the quality of the sound, too, but he seemed to like it well enough. He did have someone else put a reed in it though, I think it was Kevin Thompson. Memory’s a bit fuzzy now…
Consider a C chanter. Definitely quieter.
Yeah, seriously, C, B, or Bb is the best way to go if you want to decrease your risk of being smothered with a pillow in the middle of the night. 
The Rogge “narrow bore” D is really more of a medium bore, narrower than the big bores but not as narrow as say a Wooff or Angus quite narrow bore D chanter, which are quiet and more like a C chanter. Note that there are larger and smaller bore variants of all the pitches with varying volumes as well. There is nothing generic about the UPs.
Ted
You should have thought of that before you married her.
Royce
(Just say no to narrow D)
Well, I suppose I could divorce her…naaah, cheaper by far just to buy a quieter stick.
Would a narrow bore C chanter be OK, Royce?
unionpiper,
my narrow bore D chanter is much quieter than my concert
by far, at least half the volume. all the best stew. 
Don’t guess. I’ve posted some readings taken with a decibel meter.
Even more than the bore is the reed, though. And granted, a narrowER reed tends to work better in a narrowER chanter, but you can put a stiff reed in some pretty small-bored flat chanters and make them louder.
No, there’s no quiet UP. But I’d have to agree that there are some good flat-pitch specialists who make quietER stuff (reed plus chanter).
Stuart
I’ve an Angus narrow D, and it’s a good deal quieter than my concert pitch chanter, even with the rushes in the bore (the CP chanter, that is). The difference between concert and flat or narrow is that I can’t hear the phone ring when I’m playing the CPs. Possibly an advantage, that…
Kevin, what is the actual difference in the bore sizes? I can’t remember if you have posted that info before.
Since this question of large vs small bore seems to come up regularly, pehaps a separate FAQ would be in order. Opinions, anyone?
djm
I’d say yes, but won’t this turn into another conversation like the one I started about Coyne vs. Kenna vs. Harrington vs. . . ?
If there’s nothing in the FAQ which talks about flat vs. concert, maybe we should add something; but any comments will be sweeping generalizations.
Stuart
If you’se guys can help me with the essential issues, I’ll try and write something up for the FAQ. Here’s what I’ve deduced re: narrow and wide bores, but wouldn’t know where to begin with flat sets.
Anything else?
-gary
Snoogie, not only is the bore narrower, but quite often the tone holes are smaller too. Narrow bores are intended to be quieter than wide bores, but some narrow bores are not that much narrower, and some people deliberately increase the volume of their narrow bores by opening up the reed apperature.
I’ve a dustpan, just in case. 
djm
See the Craig Fischer article (Flat Sets: Vive la Difference!) on the Cumann na bPiobairi website. He provides a few measurements for comparison.
According to Craig, the classic narrowbore chanters from the 19th century typically have a throat diameter of about 4mm, sometimes more, sometimes less. Fischer cites the example of a Coyne with a 3.7mm throat, for instance. Exits would be about 11mm or so, give or take a few tenths. Rowsome style concert Ds are about 5mm, often as much as 5.4 or 5.5, with exits in the 12-12.5mm range. I have a Kennedy (Cork) D with a 13mm exit. So they could go even larger.
These differences may seem subtle until you hear both types in person and you try playing them.
Kevin’s anecdote about not being able to hear the phone ring while playing a concert pitch chanter is about right. I can hear the phone while playing my B set, chanter, drones, regs all at once, but I can’t hear anything when playing my CP chanter alone.
i went out wandering in den bergen last month and payed andreas rogge a visit.
i ordered a narrow bore, loved that sound. it’s the same boresize on the outside than the concert, but the holes are smaller.
andreas told me i wouldn’t be heard in a session, but he would consider a making a medium bore (he proposed this himself).
so i can still change my mind.