Paul Simon fans in Philadelphia are hearing the “Sound of Silence” instead of his voice this weekend … because he’s had to cancel two performances.

A post was shared to the singer-songwriter’s Instagram Saturday … letting fans know “chronic and intense back pain” required immediate attention — and, he can’t play his shows this weekend.

The statement explains the shows will have to be canceled for now … because PS simply doesn’t have the ability to reschedule them for a later date at this time.

He’s got more concerts set up for Los Angeles, San Francisco and Vancouver into early August … so, he has quite a bit of time to recover before his tour comes to an end.