[Translation from Japanese to English ] The lens you are using and the lens you returned have different capabilities....

Original text

あなたが利用しているレンズと返品したレンズは性能が違います。

あなたのレンズはフルタイムマニュアルで超音波モーターを利用しており、モーター音がほとんど発生しない品質、機能です。

しかし、返品したレンズはオートフォーカスを働かせる際、モーターがギアを介して動作します。
したがってこのレンズはギアを介するために音が発生します。
これはこのレンズの性能です。このギアの音を消すことはできません。

また、あなたのレンズとこのレンズはモーターの大きさも異なります。

Translation / English

The lens you are using and the lens you returned have different capabilities.

Your lens is a full time manual using ultrasonic motor, so it can function with little to no motor sound.

However, if you use the lens you returned in auto focus mode, the motor will operate through gears.
This lens produces sound because it operates using gears.
This is this lens's function. It is not possible to remove the gear sounds.

The size of the motor of your lens and this lens also differs.

Translation / English

The performance of the lens that you are using and the returned lens are different.

Your lens uses the ultrasonic motor full-time, one feature is that the motor sound rarely occours.

However, the returned lens in case that it's working using auto focus moves the motor's gear.
Therefore this lens in order to assist the gear, it produces a sound.
This is the ability of this lens. You can not eliminate this gear's sound.

Also, the size of this lens and the one you have is different.