Yes, it is safe and is well below the level in the womb (measured at 75-92dB).
The sound on the blue level is 68-70db (at the baby’s ear). The sound on the red level goes up to ~86dB which is quieter than a baby’s own cries (~100 dB, which is actually more than twice as loud as 88dB).
Happiest Baby does not provide medical advice. Please seek the advice of your
healthcare provider if you have questions regarding a medical issue.