Geminate speech sounds are exactly the same and one is said immediately after the other.

geminate consonants 双辅音，长辅音，重叠辅音

Geminates are speech sounds that are exactly the same, and one is said immediately after the other.

the analysis of initial geminates in a language 对一个语言最初的双音的分析

to repeat a speech sound

The middle consonant can be geminated. 中间的辅音可以发重叠音。