Correct

喃喃

/ nánnán / 
Strokes

Definition

(onom.) to mutter/to mumble/to murmur

Example

As an Onomatope

mumble; murmur; mutter

1
Nánnán
喃喃
bùxiū
不休

murmur endlessly

2
Nánnánzìyǔ
喃喃自语

mumble/murmur/mutter to oneself