原文是一位外國網友寫信給日立抱怨怪音所得到的回覆 , 很有參考價值 !

Dear Mr. XXXXX,
thank you for your email.

Regarding your enquiry relating to the brief sound that emanates from our
drives.

I suspect that the occasional 'sound' you are hearing is the Idle Time
Function that has been introduced on our latest drive designs as a
reliability enhancement. You need not be alarmed by this,

This "sound" is due to a brief but deliberate head arm movement every so
often. This has been added to maximise the reliability of our disk drive
products.

This function is invoked if an extended period of inactivity is detected,
so has no impact on active performance. [It is bad to leave the heads
hovering over the same data track unnecessarily].
Even after a period of time of activity the Idle Time Function can be
implemented as the Idle Time Function is a cumulative function.

The level of sound emitted may vary from one drive to another and as such
this should not give rise to concern or be considered an impending failure.

Please be assured that this drive design is one of the quietest drives, at
this data density, in the industry.

I trust this information will be of use and help you to resolve your
problem.


Regards

Catrin Schoening

Hitachi Global Storage Technologies

http://www.google.com.tw/search?q=c...+noise&hl=zh-TW

原文大意是 : 所謂的噪音是日立為了強化可靠性所引起的 , 稱為 "Idle Time Function " , 這個噪音是硬碟在偵測硬碟閒置時移動讀寫頭的聲音(因為在不需要使用的時後將讀寫頭盤旋在固定的磁盤上是對硬碟不好的) , 這個怪音並非是日立的疏失而是為了強化硬碟可靠性所造成的 , 而且在硬碟全速運作時不會影響正常工作(有時候全速時仍會施行 Idle Time Function , 因為這是累增的功能) , 噪音的大小每顆硬碟都不一樣 , 但這都是正常的 , 所以請不用太在意 !
最後 , 這顆硬碟一定是目前工業技術中同密度硬碟裡最安靜的 !
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以上是我大致翻譯的結果希望對於看不懂英文的網友有所幫助 , 綜合以上的結論是 : 噪音人人都會有 , 若你聽不到表示你的PC本身噪音就很大 ; 而因為這是正常的現象所以看來日立也不打算提供 firmware 來修正 , 對於網路版的修正噪音 firmware 也許會破壞掉日立設計之初為了要強化硬碟可靠性的美意 , 所以我是建議不要更新 !
按照 HGST 的回覆若你聽不到此噪音表示 "Idle Time Function " 已經被關閉 , 隨之而來的就是讀寫頭會一直盤旋在固定的磁盤上 , 對於硬碟的壽命和可靠性會有所影響 !

以上文章對於所有網友好奇噪音的產生應該可以釋疑了 , 看來 IBM 那種給伺服器和工作站專用的純正血統仍然存在 , 因為在那種環境下噪音是最不被重視的 , 可靠性的提升才是唯一考量 !