Playing a low-frequency heart rate signal through a mobile speaker

Question

I am applying the application to listen to the heartbeat. I could listen to the filtered heart rate signal through the headset, but not through the mobile speaker, since the mobile speaker does not support such low frequencies, I tried the frequency offset, but this leads to sharper tones.

I need help reproducing my output signal through a mobile speaker, but without a sharp tone.

Any help is appreciated