This book develops a theory of relativity with sound signals that might attract criticism and appreciation alike. The theory is similar in spirit to Lorentz's relativity in ether and Rosen's relativities in dielectric media. In the linear approximation, Doppler shift of sound waves should be symmetric, contrary to what is believed, and a refined test of transverse Doppler shift should confirm this symmetry. Subsonic and supersonic Lorentz transformations in still acoustic medium are derived from first principles, which are then successfully applied to problems in linearized aerodynamics and astrophysics. The book is immensely readable even by non-experts.