## 1 Introduction
### Brainwaves and Sound Field  
In view of earlier studies on continuous brainwaves (CBW) [1; 2; 3; 4; 5; 6; 7; 8; 9], we shall begin our discussion from the fundamental concept of the initial time delay gap (ITDG) in a sound field, which is the time difference between the arrival of the first reflection and the direct sound [6]. We regard ITDG as the most sensitive psychological factor for listening to music. In other words, when a faint reverberation is present in a sound field, the brain is able to distinguish whether a listening target is interrupted by excessively delayed reflected energies. This creates a noticeable change in the CBW frequency within the interrupted and uninterrupted regions. We propose that this is entirely caused by changes in the firing frequency of signals transmitted between the relative neurons of the cranial nerves located in different regions of the cortex. For instance, [PERSON] and [PERSON] [10] categorized external stimuli as rational or sensible and used each type of stimuli to explore how the left and right hemispheres of the brain responded to a specific characteristic of sound. [PERSON] and [PERSON] [11] found that the peak amplitude of N1 increased alongside pitch strength. When we investigated through CWB recordings how the ITDG in a sound field affected the vestibulocochlear nerve and then compared the differences, we suggested that this was a result of psychological reactions manifested in our preference for or dislike of something [12]. This study investigated the threshold effect of psychological judgment, and therefore the most obvious responses to ITDG on the cerebral cortex should be classified as a CBW and an auditory-evoked potential (AEP), which is a response that occurs within 500 ms after the arrival of an auditory stimulus [8; 9]. Most of these responses are manifested in the transmission potential responses of nerves along the auditory pathway, that is, a sound enters from the ear canal, passes through the eardrum and ossicles, and is then converted into electronic signals (nerve impulses) at the cochlea and transmitted to the two cerebral hemispheres, where a response occurs. [PERSON], [PERSON], and [PERSON] [13] studied the AEP in terms of the slow vertex response (SVR) and revealed that the latency of the N2 peak of an SVR increased in response to changes in the magnitude of the interaural cross-correlation (IACC). They deduced that changes to the IACC caused by auditory nerve signals through the lateral meniscus on the auditory pathway would produce a latency in the N2 peak. The N2 peak was the most distinguishable peak, produced around 200 ms after a signal entered the ear canal. N1, N2, P1, and P2 were dips and peaks of the waveform in AEP responses, which were suggested by [PERSON] [9], as shown in Figure 1. In addition, [PERSON], [PERSON], and [PERSON] [14] found that, within an ideal first reflection of a sound in a sound field, the N2-latencies of SVR were prolonged in both hemispheres, while the P1-N1 amplitude in the left hemisphere was also increased. However, in this study, the continuous cueing method was used for auditory stimuli; hence, we believe that, by using the reflected energy and reflection time difference, \"reaction\" and \"non-reaction\" threshold responses can be observed for exceeding 500 ms after a stimulus through CBW recordings.