The law of reflection says that the angle both rays make with the reflecting surface are equal. Use the equations above to calculate the wavelengths of several different frequencies and discuss it with the students in terms of what types of sounds will be easily reflected. The law of reflection applies to curved surfaces like cones and parabolas. Include some curved surfaces in your demonstration. Horn shapes have been used for a very long time to improve the radiation or reception of sound waves.
Effective horns have very hard, smooth walls that absorb as little sound energy as possible.
A simple horn is not an extremely effective way to locate sounds because it is open to capture sounds from so many directions. Devices like the one shown in figure 7 have been used as directional sources and receivers of sound. Only the sound waves entering from a direction parallel to the tubes do not cancel each other out at the other end. When two waves from a source take two paths, one could get ahead of the other and would be called out of phase. In a tube, the phase velocity of a sound wave is practically equal to free sound speed, therefore all components of the sound wave through the tubes arrive in phase.