## 7 General Discussion  
The NVS scheme has been used as a cochlear implant (CI) simulator to simulate the poor spectral cue and enough temporal cues provided by a CI device [21; 22]. Since CIs are known to lack the information necessary for recognizing non-linguistic and para-linguistic information [23], the results of our study could be helpful for improving the non-linguistic and para-linguistic information recognition of CI users by increasing or decreasing specific modulation frequency components of a TAE.  
Our previous studies in which we systematically varied the number of channels in the NVS scheme and the upper limitation of the modulation frequency components [11; 12] demonstrated that the TAE plays an important role in the recognition of both vocal emotion and speaker individuality as non-linguistic information. These studies found that significant cues for perception of non-linguistic information are temporal modulation components of the noise-vocoded stimuli lower than the modulation frequency of 8 Hz. These studies also suggested that recognition of vocal-emotion and speaker individuality using the NVS scheme with NH listeners can be used to predict the response from CI listeners as CI simulators [24; 25; 26].  
In this paper, we found with experiments I and II that NVS contains features that contribute to a sense of urgency as para-linguistic information. The perception of urgency might also involve human perceptual mechanisms of amplitude modulation. Additionally, according to the results of experiment III, the modulation frequency component of a TAE that contributes to the perception of urgency is from 6 to 8 Hz. [PERSON] et al. previously showed that the modulation frequency of speech peaks near 4 Hz regardless of language [21], which suggests that the modulation frequency of linguistic information is near 4 Hz. Our own findings thus indicate that the modulation frequency component of contributing to urgency perception is higher than that of linguistic information.  
Our experimental findings indicate that even para-linguistic information might not be completely unrelated to linguistic information. For example, the results of experiment IV suggest that the sense of urgency may also be lost due to the loss of the linguistic information of speech stemming from the use of reversed speech. However, the modulation frequency components at the core of linguistic information and those important for the perception of urgency differ, as noted above [23]. Therefore, it is unlikely that the loss of a sense of urgency observed in experiment IV is related to the loss of linguistic information of speech.  
We should mention that the modulation frequency observed in experiment III was calculated in the sense of a long-time average. Therefore, if the modulation frequency component in a TAE of speech plays an important role in the perception of urgency, it should be possible to perceive urgency even in a speech where the temporal direction is reversed. The results of experiment IV suggest that this was not the case, however, which leads us to suspect that the instantaneous modulation frequency (e.g., temporal variation of modulation frequency, asymmetry of its variation pattern, the difference between rising and falling edges, etc.), as well as the modulation frequency component calculated in the sense of a long-time average, are important cues for the perception of urgency. This is our future work.