Square wave audio out from the hearing device!

[alec_t]

Your output transistor is being driven into saturation. Try increasing R9 (sim shows distortion becomes significant when R9 < 100Ω).

 

[audioguru]

1) Your class-A output amplifier is clipping because its input level is too high.
2) Its load resistance is much too low for it to have a 220 ohm collector resistor. 40 ohms is dynamic (coil and magnet) not ceramic.
3) Its gain is too high so its distortion is also high.

The output capacitor value is much too low so it passes mostly distortion harmonics.

I fixed it but since it is a simple class-A transistor its distortion is fairly high. A properly designed class-AB output will have distortion that is so low it cannot be heard.