## 1 Introduction  
In daily life, we often need to interpret speech that is interrupted or accompanied by other sounds. Various studies have been performed to investigate how humans are able to interpret speech when it is spoken in a noisy environment [1; 2], or under reverberation [2; 3]. A wealth of research has particularly been performed on temporal aspects of speech processing, by using speech in which parts of the signal were segmented or omitted. An early study on the perception of distorted speech employed speech in which 50-ms portions were alternately played and silenced [4]. Surprisingly, despite the silent gaps, listeners could still extract some meaning from the signals. Further studies on such \"gated speech\" showed that even if the 50-ms silent gaps were removed and the remaining speech portions were contracted, the speech could still be intelligible [5; 6]. Besides periodically interrupted speech, processing of distorted speech has further been investigated with speech that was temporally smeared [7; 8] or temporally reversed [9; 10]. Of particular interest is the perception of locally time-reversed speech. In locally time-reversed speech, speech was segmented into short portions of, for example, 50 ms. Following this, each segment was reversed in time, connected again, and presented to the listener [11; 12]. Studies have shown that the intelligibility of locally time-reversed speech was near zero when the segmented portions were about 100 ms or longer. For shorter segments, however, intelligibility sharply increased and became very high (>90%) for segments of about 40 ms or shorter, if the speech rates were normalized [13; 14]. A study with \"pixelated speech\" also showed that when speech is divided into segments of 50 ms or shorter, almost the same intelligibility can be obtained as for the original speech [15]. During the last decades, auditory neuroscience research has added new insights into temporal aspects of speech processing, by proceeding from speech units based on phonetic segmentations [16], articulatory features [17], or syllables [18]. Especially the importance of neural oscillations in cortical speech processing has been stressed, in particular of those with a modulation frequency-range around 30-50 Hz [19]. Neural oscillations with this modulation frequency are thought to be engaged in phonemic processing [20]. Interestingly, the modulation frequency of these neural oscillations corresponds to a temporal window of around 20-33 ms [21], which corroborates the idea that the human auditory system processes speech in relatively rough time segments. Both neuroscientific studies and studies based on psychophysical methods on locally time-reversed speech thus suggest that the duration of these time segments is about 40 ms or shorter. Recently, a new type of speech stimulus, called \"mosaic speech\" [14] has been developed to further study speech processing in general and its temporal aspects in particular. One of the purposes of using \"mosaic speech\" was to provide an alternative to locally time-reversed speech, because local time-reversal can leave some unintended cues, as well as distortions, about the spectral content of the speech signal. By performing listening experiments with mosaicized Japanese speech, in which the frequency resolution was as fine as a critical bandwidth, [PERSON] et al. [14] found that intelligibility was near-perfect (>95%) at shorter block durations of up to 40 ms, similar to the results of studies with locally time-reversed speech. Intelligibility decreased dramatically at longer block durations, from 80 to 320 ms [14]. Although the intelligibility of locally time-reversed speech and the intelligibility of mosaic speech were similarly dependent on segment duration, mosaic speech, for which intelligibility was systematically higher, is considered as more suitable than locally time-reversed speech to investigate the temporal nature of speech perception. In locally time-reversed speech, the content of each reversed temporal segment is never static.