My wife's grandmother owns a pug. Same deal when she visited. My dad used to bird hunt. Same deal as getting a dog used to the shotgun. Just give it time.
The trick will be getting the dog to lament in harmony to your tuba playing!
When a dog is in its puppy stage (birth to about 6 months) it will accept most anything with just a sniff, but as it gets older the acceptance gets harder to find. I remember the first time my dog saw a person with a hood on...he wouldn't stop barking! In order for me to get him used to it I had to spend hours training him to accept a hooded person. To do this I would start wearing one around the house or putting a cap on outside. He knew I wasn't going to hurt him, but he couldn't understand why there was a suspicious looking thing on my head. Eventually he learned to accept it. That might be what you have to do. Since your dog is unfamiliar with tubas just start playing it in another room or setting it out in the middle of the room and walking around as if it's furniture. Maybe put him outside while you play so he can hear it but not see it. Eventually he should accept it. BUT all dogs are different so you never know if he'll ever fully accept it.
When Lucy was a pup, she sniffed the horn, watched me pick it up, then barked when I played. 5 years later, she still follows me upstairs and "accompanies" me when I practice. However, when my wife plays her trumpet, Lucy throws her head back and really howls, especially from high C and above.
I had the same problem: terrified dog. The moment I picked up my mouthpiece, the dog would run and hide.
I took advantage of how much the dog loved treats. I tried feeding the dog treats out of the mouthpiece in my hand. (Depending on one's views on sanitation, one might consider washing the mouthpiece either before or after.) That seemed to reduce the fear of the instrument itself.
Then, I started giving the dog a treat immediately after I finished practice. After a while, the dog figured out that tuba practice meant a treat was going to follow. Now, the dog camps out just outside my practice room, so it can be ready for the treat when practice is done. I like to think that the dog's musical taste has improved.
Don't dwell on it, just let the dog get used to it.
It may or may not happen--but you're not going to change things much either way. We fostered a dog who was scared to death of wastebaskets. One of our dogs was terrified by the vacuum cleaner. Given time, the dog will find some way to cope.
Just be happy you don't have a cat that hates tubas.
My neighbor's dog started coming over when I practiced music on anything. Now I can't get rid of her. It could be the baloney my wife slips her when our cat isn't looking.
I put some cat ears on my head that my grandson got on halloween. The cat was terrified. He musta thought I was turning into a really big cat.
Our Dixieland group rehearses here on Saturday mornings. Both of my cats hang around until the music starts... then they retire into hiding. As soon as rehearsal is over, they come back out. Must be something to do with overtones!
Dan Schultz
"The Village Tinker" http://www.thevillagetinker.com" target="_blank
Current 'stable'... Rudolf Meinl 5/4, Marzan (by Willson) euph, King 2341, Alphorn, and other strange stuff.
I'm reminded of an anecdote of a famous NYC violinist who used to give lessons in his home. He had a dog that would howl whenever his students would hit wrong notes. One day as a favor to an old friend, he started teaching a beginning student, who didn't play a correct note. Yet during the lesson the dog remained silent. Upon investigation, he discovered his dog had died.
Seriously, you might look at some dog training books for beagles, especially sections dealing with gun shy beagles. You might find some suggestions there. Being patient and encouraging like others have suggested, might also help.
Then again, I've had 8 dogs in my life - all who would run away and hide at the first sound of a vacuum cleaner. What's the harm if the dog chooses to go into another room and hide while you practice? Unless of course he gets so scared and physically ill when you play that you are concerned about the welfare of the dog - that's not good for you or the dog.
One of my dogs was beagle. She was one of the most lovable and most stubborn dogs I ever had. Good Luck!