If an AC motor is making irregular noise, it may be due to one or more of the following reasons:

1. Bearing issues: The motor's bearings may be worn or damaged, causing irregular noise.

2. Misalignment: The motor shaft may be misaligned, causing the motor to vibrate and produce irregular noise.

3. Loose components: The motor's mounting bolts, shaft couplings, or other components may be loose, causing irregular noise.

4. Electrical issues: The motor may have electrical issues such as damaged windings or a faulty starter, causing irregular noise.

5. Overloading: The motor may be overloaded due to excessive load or a mismatch between the motor and the load, causing it to produce irregular noise.

6. Mechanical issues: The motor may have mechanical issues such as misaligned or damaged rotors, causing it to produce irregular noise.