To provide the distance information of a sound source in virtual audio space, we must have some information about effective distance cues and there must be some way to handle them properly. It is well known that the conventional cues comprise loudness, spectral information, reverberation and binaural information. Some research works have shown that most of these cues can give listeners only limited distance information. Among these cues, reverberation can give listeners effective distance information, but the implementation using this cue is not a simple problem because there are no well-defined parameters and methods. This paper discusses methods to control the perceived auditory depth with the reverberation cue. A two-stepped linear envelope method and an artificial reverberator, which can control the early reflection slope of an impulse response but does not alter the reverberation time, are proposed as solutions. To validate these methods, subjective assessment was performed.

Over the last twenty years, 3-D audio technologies have advanced significantly despite the difficulties in implementing them. However, their performance in providing information, especially about the distance of a sound source, remains imperfect. Therefore, more researches on distance cues are indispensable to achieve more effective technology. In this paper, we try to show how the conventional cues change as the distance of a sound source varies, by means of measured impulse responses using the swept-sine method and modeled impulse responses using CATT Acoustics. It is well known that the conventional cues comprise loudness, spectral information, reverberation and binaural information. Among these, we focus on the reverberation cue to describe the distance of a sound source. Some researches have shown that reverberation can give listeners absolute distance information, but the implementation using this cue is unfeasible because there are no well-defined parameters. In this paper, we also try to validate reverberation as a feasible distance cue by suggesting early decay time (EDT) and clarity index, C80, as the parameters for controlling the perceived distance with the reverberation cue.