Reflected Sound: Friend or Foe

Sound-reflective surfaces are everywhere in natural environments. Objects, walls of a room, even our own bodies are all examples of sound-reflecting surfaces. What we hear in natural environments from a source of sound is therefore a complex combination of sound that reaches our ears directly from the source and sound that has been reflected from one or more surfaces. The trouble is, what if we only are interested in the direct sound? Then reflected sound is unequivocally viewed as a contaminant. This is true for many situations, from measurements of loudspeaker responses to understanding speech in natural environments. In other situations, however, reflected sound can provide valuable information about the listening environment that can enhance sound quality and improve abilities to localize the sound source. The purpose of this article is to discuss the many ways in which reflected sound contributes to our listening experiences, both positive and negative. Although the focus is largely on humans listening in air, many of the topics discussed have parallels in other species and through other media.