performance
Detecting space conditions
from phase-contrast by using sine waves and a gate on various sounds
minoru sato (m/s) + toshiya tsunoda
Dec.1997 at uplink factory in Tokyo
Sound, from the point of physics, as a
wave/vibration phenomenon, propagates in any space where medium (matter)
exists. In the propagation process, for example, in a space with elements
(such as; walls, a floor, a ceiling and so on), some reflection and diffraction
of the sound will arise. These effects appear as a phase-contrast and
are, of course, observable in the space. The phase-contrast is generated
by 1) the difference in the distances between a direct course from the
sound source and several courses via reflection & diffraction, 2)
the phase change which depends on any fluctuation of boundary conditions
of the elements when the reflection or diffraction arises. The contrast
mostly appears as any fluctuation of amplitude (changes in the loudness
of the sound). Even the loudness of a sine wave from an oscillator changes
with any motion of the elements. For this reason, observing the phase-contrast
at a fixed location becomes an index to dynamically measure the conditions
of a space.
In this work, the volumes of the sine waves (from the oscillators) are
fixed and played in the performance space. At the same time, the sound
waves in the space are recorded at a particular location in the space.
Later on, the recorded sound is played back through a custom-made gate
modulator. When the amplitude of the sound passes through a particular
gate level, only parts of the recorded sound can pass through the gate.
If we hypothesize that the elements have no movement, then the recorded
sound becomes a fixed amplitude. If so, it is either possible or impossible
for the sound to pass through as a whole. When the space condition changes
(some movement of the elements, as well as, the movement of observers/audience),
the change effects the phase-contrast. In a way, when the change is comparable
to the motion of the sine wave from the oscillators, some fluctuation
also affects the recorded sound.
What we can find, in this way of detection of the condition of a space,
is that it might make clearer, how we are concerned with a space and its
components (elements, such as walls, etc), each as a function and an activity
of the conditions of a space. Finally, in the result, we can hear the
whole activity of a given space. (text by m/s)
ここでは、空間内にある一定の時間、一定の音圧の発振音を放つ。その波動を２つのマイクロフォンを用いて、２点間にて記録する。記録された２点間における音声信号を比較可能にするため、振幅ゲートモジュールを用いて、ある振幅値を越えた信号のみを取り出し、再生する。 一定の音が一定の空間内を伝搬するとき、その空間内の諸要素が「運動をしない」と仮定すれば、記録された信号の振幅変化は一定となる。つまり、ゲート値を如何なる値に設定しても、再生される信号はある一定の振幅を保つ。空間内の状態が変化したとき、つまり何らかの運動 -この場合、観測者自身の運動や発音行為により励起された諸要素の運動をも含めなければならない- が生じたとき、その変化は２点間の位相差に影響する。もし、この運動が発振音の波動運動に対して十分な大きさであれば、振幅ゲートモジュールを通して取り出される信号も、大きく変化する事になる。
このような空間の状態の検出方法より、何が窺えるのであろうか？恐らくこのパフォーマンスでは、空間の諸要素としてその空間に参入する私達が、如何にその空間の性質として機能し、そして如何にその空間の状態として活動しているのかが、明確になるのであろう。その結果、私達は、私達が関わる空間に関する、空間全体の活動を聞くことになるのである。(text by m/s)