VOLUME: 17
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HIGH SCORE: 0
In Pursuit of
完美寧靜空間
The
tranquility of libraries is no match for
the anechoic chamber (echo and reverberation
free) at Minnesota’s Orfields Laboratory. Measuring
at -9.4 dB (decibles), the room made its mark in the
Guinness Book of Records as the “quietest room
on Earth” and is insulated to any external sounds
by means of suspension and sound absorbing
material. To put that into perspective, the human
ear stops detecting sound at 0 dB. In fact, the lack
of noise is so intense and derailing that reputedly,
no one has ever been in the room for longer than
45 minutes. Recently, a finer sound absorbing
dev ice was cons t r ucted, g i v i ng an equal l y
promising performance with applications beyond
sound absorption.
As it turns out, too much peace and quiet isn’t
all it’s cracked up to be. The muted environment in
the anechoic chamber amplifies the feeling of the
tiniest sounds – from heartbeats to intestinal noises -
bringing disorientating acute awareness to sounds
that would otherwise not be heard. Imagine
suddenly being able to hear your own lungs or the
rush of your blood pumping. The chamber comes
equipped with a chair, because even standing
is apparently too disor ientating as your ears
subconsciously use surrounding sounds to balance.
Sound waves are essentially vibrations of an
object and can be transmitted through air, liquids
or solids. Waves are propagated by subsequent
美
國明尼蘇達州的Or fields「零回音室」內寧靜無
比。房間通過獨特設計和吸音物料，隔絕了外界的一切聲
音，室內音量只錄得-9.4分貝，贏得健力士世界紀錄中的
「地球上最安靜的房間」的稱號。要知道人類耳朵所能聽到
的最低音量是0分貝。這無聲環境讓人無法忍受及產生幻
覺。據說，從來沒有人能在房間內逗留超過45分鐘。最近有
科學家製造了一個更精細的吸音裝置，具備同樣性能且可以
應用在其它方面。
過於寧靜並不是想像中的好。在「零回音室」的靜音環
境中，心跳和腸臑動等微細聲音都會被放大，清楚感應到平
常聽不見的聲音，令人不知所措。想像一下突然能夠聽見自
己的呼吸和血液泵動的聲音時，你會有甚麼感覺？耳朵慣常
是以周圍的聲音來保持平衡，在這裏光是站立也會迷失方
向，所以房間內設有椅子。
聲波本質上是物件的振動，可以通過氣體丶液體或固體
來傳送。聲波傳播依靠分子間的碰撞，這樣解釋了聲音為何
不能在真空傳播。「零回音室」是以一層層厚厚的混凝土和
鋼材阻隔外來的聲音，但真正消除迴聲或混響的關鍵，是內
裏交叉覆蓋著有吸音功能的梯度折射率纖維。發泡材料和海
綿也常作此用途，但它們既佔空間又不耐用。
去年，香港科技大學的研究員於《自然—材料學》發表
論文，介紹一種可以完全吸收聲波的聲學超表面。薄薄的超
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Ready!
By Thomas Lee
李浩賢
