Some Technical References for the propagation of sound in ducts and acoustic filters are:

• "The Propagation of plane sound waves in narrow and wide circular tubes, and generalization to uniform tubes of arbitrary cross-sectional shape," M. R. Stinson J. Acoust. Soc. Am. 89, 550-558 (1991) (and references therein).
• "Propagation of sound waves in ducts," F. Jacobsen, Acoustic Technology, Ørsted•DTU, Technical University of Denmark, Note no 31260, 2006. (71 pp.) ("Lecture Notes").
• "Active Impedance Control for One-Dimensional Sound," D. Guicking and K. Karcher, Trans. ASME: J. Vibration, Acoustics, Stress, and Reliability in Design, Vol 106, 393-396 (1984).
• "Acoustic Wave Filters," G. W. Stewart, Physical Review 20, 528-551 (1922).
• "Nonlinear oscillations of a gas in a tube," M A Ilgamov, et al., Appl. Mechanics Rev. 49, 137-154 (1996).
• Plus see general references.

This is not intended to be a complete list, just one to get started.