![]() ![]() , who argued that spectral detail is not as critical in the reverberant sound as it is in the direct sound. Monaural cues have been shown to have limited importance by Hassager et al. Previous studies have looked into the contribution of both monaural and binaural cues to the externalisation of reverberant binaural signals. It has been suggested that this effect can be achieved even by just adding the early reflections, while the contribution of late reverberation (>80 ms) is smaller in comparison. When reproduced binaurally (e.g., through headphones), it has been shown that reverberation increases the sense of externalisation, i.e., the illusion of virtual sound sources being outside the head, when compared to anechoic sounds. showed that this assumption may not always hold and directionality should be taken into account, especially for asymmetrical spaces, such as a corridor. Although late reverberation is often modelled as diffuse and isotropic (i.e., with an even distribution of energy across directions from the listeners’ point of view). suggested that RT contributes to the perception of environment dimensions most significantly in large spaces, whereas early reflections have greater importance in small rooms. An important parameter used to define such process is the reverberation time (RT), or the ‘duration required for the space-averaged sound energy density in an enclosure to decrease by 60 dB after the source emission has stopped’, which is generally proportional to the volume of the room. At this point, temporal and spatial features of individual echoes become less relevant, and late reverberation can be characterised as a stochastic process. found that it was correlated with the perception of environment dimensions and ‘presence’-or ‘sense of being inside an enclosed space and feeling its boundaries’-while in the case of concert halls, Beranek linked it to a sense of ‘intimacy’.Īs time passes and the sound waves that emanated from the source continue interacting with the environment, the temporal density of echoes increases, and the resulting sound field becomes more diffuse. The time delay between the direct sound and the first distinct echo has also been shown to be a relevant feature: in the case of small rooms, Kaplanis et al. For example, Barron and Marshall argued that the timing, direction of arrival, and spectra of early lateral reflections contribute to the sense of ‘envelopment’-defined as the ‘subjective impression of being surrounded by the sound’. ![]() Such phenomena can alter the perception of the room on a higher level. Furthermore, they can modify the signal’s spectrum due to phase cancellation and subsequent comb filtering, as shown by Bech in his study on small-room acoustics. Nevertheless, early reflections can broaden the perceived width of the source and shift its apparent position, as shown experimentally by Olive and Toole. , the maximum delay after which a reflection is no longer ‘fused’ with the direct sound depends on the signal, being around 5 ms for single clicks and as long as 40 ms for complex signals such as speech or music. According to the so-called precedence effect, the direct sound allows a listener to determine the position of the sound source, while early reflections are generally not perceived as distinct auditory events. Thus, a listener will receive filtered replicas of the original wavefront (echoes) arriving from various directions at different times, causing the impression that the original sound persists in time. After emanating from the source, a sound wave will interact with its environment, undergoing reflection, diffraction and absorption. Reverberation results from pairing a sound source with an acoustic space. ![]()
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