The term “critical distance” refers to the distance from a loudspeaker in an enclosed space at which the reverberation is equal in strength to the direct sound from the speaker. Beyond this distance, the reverberant energy tends to mask the direct sound. In truth, because reflected sound loses energy to boundary absorption (and also travels a longer path to the listener, thus incurring greater air absorption losses), the reverberant energy from a discrete pulse sound stimulus can never equal the direct sound on an instantaneous basis. In highly reflective environments, however, the steady-state reverberation strength can easily exceed that of the direct sound at many locations in the space. This degrades the signal-to-noise ratio and destroys intelligibility. Return to