2 sentences for 沉闷 (chén​mèn — muffled)

1. 远处传来了沉闷的雷声。

   yuǎn​chù chuán​lái le chén​mèn de léi​shēng.

   Dull rolls of thunder could be heard in the distance.

   Source: Dong Chinese Dictionary

2. 他感觉自己的心口窝有一阵沉闷的疼痛。

   tā gǎn​jué zì​jǐ de xīn​kǒu wō yǒu yī zhèn chén​mèn de téng​tòng.

   He felt a dull pain in the pit of his stomach.

   Source: Dong Chinese Dictionary