钟摆声 Sound of a pendulum

最近早上完成一系列收拾活动后坐在桌边放空一分钟的时候总是会听到类似时钟的秒针转动的声音。但这一定不是时钟的声音：我的桌上（和我的房间里）并没有时钟，除了一个电池已经消耗殆尽的电子钟以荧幕空白的方式出现在床边柜上。那这是什么声音呢？我刚才将这种吸引了我注意力的微弱声音纳入观察范围的主要原因是他似乎有一种规律性，这种规律性也是我刚才做出“听到类似时钟的秒针转动的声音”这个猜测的依据：还有什么比时钟的秒针的运动要更规律呢？但这个声音的规律会突然被打乱，从与秒针运动间隙差不多的规律逐渐变快，变密集。在密集的程度几乎要达到一种连贯的、无间隙的单频率音调时就停止了。我把耳朵贴在桌面上观察着这个声音的来源。我找到了：是刚盛满热水的水杯底部的轻微凹陷处残留的热水在其与桌面这个平面形成的狭小密闭空间里受挤压而发出的（或许是气泡尝试离开）的声音。

I always hear the sound of a clock’s second hand ticking when I stare blankly at my desk for a minute after a series of morning clean-up activities. It must not be the sound of a clock: there is no clock on my desk (and in my room), except for an electronic clock with a dead battery that appears on the bedside table with a blank screen. What is the sound?  The main reason I just brought this faint sound that caught my attention into the range of observation is that it seems to carry a rhythmic pattern; such regularity is also the basis of my previous speculation of “hearing the sound of a clock’s second hand ticking”. What could be more regular than the movement of the second hand of a clock? But the precise rhythm of this sound will suddenly be disrupted, from a movement similar to that of a clock to one that gradually becomes faster and denser. When the intensity is about to perform a coherent, seamless pitch of a single frequency, it stops. I moved closer and put my ear on the table to look for the source of the sound. I found it: it was the sound of hot water left in the slight indentation at the bottom of a glass cup just filled being squeezed (perhaps it is the air bubbles trying to leave) in the small, enclosed space between the glass and the flat surface of the table.