Concerning ‘sound’; it is defined as one among several wave/vibration phenomena dependent on the natural scientific theory. This means physical wave/vibration phenomena where the motion follows the dynamics described by wave-equation formula in physics. As the phenomena assembled under this concept concern the general dynamics described by ‘wave/vibration’ we may find it a bit odd to name all ‘wave/vibration’ phenomena ‘sound’. Because the term ‘sound’ usually refers to wave-phenomena propagating in air, and the term also includes the physiological meaning where the wave phenomena are in an audible frequencies area as the condition on auditory sense. Anyway whether the physical definition or the physiological definition, we are able to regard any definition as a criterion of sound. Still, we could regard the physiological definition as a bit vague compared to the physical definition. Strictly speaking it is difficult to distinguish between a perception of wave/vibration phenomena through the auditory sense or any other sense organs. Also it might be possible to discover that some wave/vibration phenomena, which are not air vibrations, can be heard as sound. In this sense, we could say that the physical definition is the most normalized criterion of demarcation for ‘sound’.

There is a system that translates ‘sound’, as defined above, into other physical phenomena, that are more transportable/conveyable - in order to attempt to reappear in different situations of time and space. We have acquired the technology for this and usually call it ‘audio transmission system’. This system transposes sound and enables a high possibility of reappearance and transportability. According to this transposition the concept of ‘sound’ maintained by physics vanishes. In a way, sound in the process of audio transmission is no sound. Moreover, when it reappears it happens under some limitation. And we may face the problem whether we can call this process reappearance’ or not. Finally we can talk about the specific limitation of the reappearance, seen from the aspect of physical phenomena. In our personal work we reflect this relation between sound as a physical vibration and the special features brought about by the audio transmission system.