The signal is too bad — I can't make out what you're saying.
Tips
grammar
Potential complement structure: 听 ('hear') + 不 + 清 ('clear') = 'unable to hear clearly'. The positive form is 听得清 ('can hear clearly'). Same pattern as 看不清 (can't see clearly) and 听不懂 (can't understand).
usage
The go-to phrase on bad phone connections, in noisy rooms, or on video calls. Often paired with 信号不好 or a request: 你能再说一遍吗?
