Correct
突突
/ tūtū /
Strokes
Definition
(onom.) beating of the heart/pitapat/pulsation of a machine
Example
As an Onomatope
［sound of a running engine］ chug
1
Fādòngjī
发动机
tūtū
突突
de
地
fādòng
发动
qǐlai
起来
le
了
。
The engine started, chugging.
As an Onomatope
［sound of heart beating］ pit-a-pat
2
Wǒ
我
tīngdào
听到
nā
那
xiāoxi
消息
xīn
心
tūtū
突突
zhí
直
tiào
跳
。
My heart jumped when I heard the news. / My heart went pit-a-pat at the news.