I know the formula RT60=(.049)V / Sa to calculate the reverb times of a room but does anyone know where the (.049) comes from and how it fits into the equation?

Its a constant. But I do not know where it derives from.

Most likely the constant is experimentally derived. Meaning some scientists had the basic equation worked out and did a bunch of experiments, and found the best constant.

i know that it is a constant but i was taking an acoustics class last semester and the book you mentioned was the book we used. but we could recieve extra credit if we figured out where it came from...

i never figured it out.

I'm also doing an acoustics module as part of my degree course and we use that same book, along with Acoustics and Psychoacoustics, by Howard Angus. No mention of where that constant comes from here either...

Regards,

Neil.