What’s that ringing in your ears? - Marc Fagelson

譯者: Lilian Chiu 審譯者: Yi-Ping Cho (Marssi)

Arriving home after a long day, you settle in for a quiet evening alone.

過完漫長的一天之後回到家，

你安頓下來準備獨自 渡過安靜的夜晚。

But instead of the sound of silence, you hear a constant ringing—

但你聽到的不是一片寂靜， 而是不停的鳴響——

even though there’s nothing making any noise.

即使沒有東西製造任何噪音。

What you’re experiencing is called tinnitus,

你經歷到的就是所謂的耳鳴，

the perception of a noise like ringing, buzzing, hissing or clicking

察覺到像鳴響聲、嘈雜聲、 嘶嘶聲，或卡嗒聲之類的噪音，

that occurs without any external source of sound.

卻不是來自任何外部的聲源。

Tinnitus has been bothering humanity since Ancient Babylon,

打從古巴比倫時代開始， 耳鳴就開始煩擾人類了，

plaguing everyone from Leonardo da Vinci to Charles Darwin.

從達文西到達爾文都是受害者。

Today, roughly one in seven people worldwide

現今，全世界大約有七分之一的人

experiences this auditory sensation.

正在經歷這種聽覺感知。

So where does this persistent sound come from?

所以，這種持續的聲音來自何方？

When you normally hear something, sound waves hit various areas of your ear,

你通常會聽到聲音是因為

聲波擊中你耳內的各個區域，

creating vibrations that displace fluid inside the cochlea.

造成震動，

使耳蝸中的液體移動。

If the vibrations are large enough,

如果震動夠大，

they elicit a chemical response that transforms them

便會引發化學反應，

將震動轉變成為生物電訊號。

into bioelectrical signals.

These nerve impulses are then relayed through the hearing pathway to the brain,

接著這些神經衝動（脈衝）

會透過聽覺路徑傳遞到腦部，

where they result in the sounds we perceive.

在腦部就會產生我們察覺到的聲音。

However, in the vast majority of tinnitus cases,

然而，在大部分的耳鳴案例中，

the nerve signals that produce these mysterious sounds

產生這些神秘聲音的神經訊號

don’t travel through your ear at all.

完全不會經過你的耳朵。

Instead, they’re generated internally, by your own central nervous system.

反之，它們是由 你自己的中樞神經系統

在你體內生成的。

Under usual circumstances, these self-produced signals

在一般的情況下， 這些自行產生的訊號

are an essential part of hearing.

是聽力很重要的一部分。

All mammals demonstrate on-going neural activity

所有哺乳類動物的整條聽覺路徑上

throughout their hearing pathways.

都會一直有神經活動。

When there are no sounds present,

當沒有聲音出現時，

this activity is at a baseline that establishes your neural code

這種活動就處於基線，

基線代表寂靜的神經編碼。

for silence.

When a sound does appear, this activity changes,

一旦出現聲音，這種活動就會改變，

allowing the brain to distinguish between silence and sound.

讓腦部可以區別出 寂靜和聲音的差別。

But the auditory system’s health can affect this background signal.

但聽覺系統的健康有可能 會影響到這種背景訊號。

Loud noises, diseases, toxins, and even natural aging

巨大的聲音、疾病、

毒素，甚至自然老化，

can damage your cochlear cells.

都可能會損害你的耳蝸細胞。

Some of these may heal in a matter of hours.

有些細胞在幾小時內就會癒合。

However, if enough cells die, either over time or all at once,

然而，如果太多細胞死亡，

不論是逐漸死亡，或一次同時死亡，

the auditory system becomes less sensitive.

聽覺系統都會變得比較不敏感。

With fewer cochlear cells relaying information,

當傳遞資訊的耳蝸細胞減少，

incoming sounds generate weaker nerve signals.

進來的聲音所產生的 神經訊號就會比較弱。

And many environmental sounds can be lost completely.

許多環境聲音還會完全遺失。

To compensate, your brain devotes more energy to monitoring the hearing pathway.

為了補償，你的腦部

就會用更多能量來監視聽覺路徑。

Just like you might adjust the knobs of a radio,

就像你可能會去調整收音機的旋鈕，

the brain modifies neural activity while also tweaking the tuning knob

腦部也會修改神經活動， 同時微調旋鈕，

to get a clearer signal.

以取得更清楚的訊號。

Increasing this background neural activity is intended to help you process

增加這種背景神經活動的目的

是要協助你處理較弱的聽覺輸入。

weak auditory inputs.

But it can also modify your baseline for silence—

但這麼做也有可能會 修改你的寂靜基線——

such that a lack of sound no longer sounds silent at all.

導致「沒有聲音」 聽起來完全不像是寂靜。

This is called subjective tinnitus,

這就是所謂的「自覺性耳鳴」，

and it accounts for the vast majority of tinnitus cases.

大部分的耳鳴案例都屬於這一種。

Subjective tinnitus is a symptom associated with

幾乎所有已知的耳朵相關疾病

practically every known ear disorder,

都會有自覺性耳鳴的症狀，

but it isn’t necessarily a bad thing.

但那不見得不好。

While its appearance can be surprising,

雖然自覺性耳鳴的出現 會讓人感到驚訝，

subjective tinnitus has no inherently negative consequences.

但它本身並沒有負面的影響。

But for some, tinnitus episodes can trigger traumatic memories

但對某些人來說，耳鳴發作會觸發

創傷性的記憶或讓人苦惱的感受，

or otherwise distressing feelings,

which increase the sound’s intrusiveness.

因而增加聲音的煩擾程度。

This psychological loop often leads to what’s known as “bothersome tinnitus,"

這種心理迴圈會導致

一般所知的「困擾性耳鳴」，

a condition that can exacerbate the symptoms of PTSD, insomnia,

這種病症會讓創傷後壓力症候群、

失眠、焦慮，及憂鬱的症狀加劇。

anxiety, and depression.

There’s no known cure for subjective tinnitus.

自覺性耳鳴目前沒有已知的療法。

So the most important thing doctors can do

所以，醫生能做的最重要的事，

is help people understand this auditory event,

就是協助患者了解這種聽覺狀況，

and develop neutral associations with these often-distressing sounds.

並針對這些讓人煩擾的聲音 發展出有中和作用的關聯性。

For example, sound therapy uses noises like rain, birdsong, or music

比如，聲音治療會使用噪音，

如雨聲、鳥鳴、音樂，

to mask tinnitus and reduce stress.

來遮蔽耳鳴並減少壓力。

One form, called informational masking, uses soothing, complex auditory signals

有一種形式叫做資訊遮蔽，

用讓人寬心、複雜的聲音訊號

that distract the brain from the tinnitus sound.

來讓腦部分心，不去注意耳鳴聲。

Another, called energetic masking,

還有種形式叫能量遮蔽，

uses sounds with the same frequency as the patient’s tinnitus

採用和患者耳鳴同頻率的聲音，

to occupy the neurons that would otherwise deliver the tinnitus signal.

來佔據本來會傳遞 耳鳴訊號的神經元。

Practiced alongside counseling,

這些介入治療方式再搭配諮詢，

these interventions allow people to re-evaluate

能讓患者重新評估 他們和耳鳴的關係。

their relationship with tinnitus.

Losing the sound of silence can be troubling to say the least.

再怎麼說，失去寂靜的聲音 都會讓人感到煩擾。

Tinnitus reveals that your brain is constantly analyzing the world around you,

有耳鳴就表示，

即使你的腦部無法過濾掉 它自己的內部噪音時，

even as it fails to filter its own internal noise.

也仍然不斷地分析你周遭的世界。

In a sense, experiencing tinnitus

在某種層面上，聽到耳鳴

is like eavesdropping on your brain talking to itself—

就像是偷聽到你的腦部 在跟它自己說話——

though it may not be a conversation you want to hear.

不過那可能不是 你想要聽見的對談。