Introduction:
In the context of electric motors, there are different types of induction motors available, including capacitor-start induction motors, split-phase motors, and permanent split capacitor (PSC) motors. Each of these motors has its own characteristics and advantages. When comparing these motors, it is important to consider factors such as efficiency, cost, noise, and power factor.

Explanation:
1. Efficiency:
- Efficiency refers to the ability of a motor to convert electrical energy into mechanical energy.
- Permanent split capacitor (PSC) motors generally have lower efficiency compared to capacitor-start induction motors or split-phase motors.
- This is because PSC motors have a fixed capacitor that remains connected during the motor operation, resulting in a constant current flow through the auxiliary winding.
- This constant current flow creates additional losses and reduces the overall efficiency of the motor.

2. Cost:
- When it comes to cost, permanent split capacitor (PSC) motors are generally more cost-effective compared to capacitor-start induction motors.
- PSC motors have a simpler design and require fewer components, which helps in reducing the manufacturing cost.
- On the other hand, capacitor-start induction motors require additional components such as a starting capacitor and a centrifugal switch, which can increase the overall cost of the motor.

3. Noise:
- Permanent split capacitor (PSC) motors are known for their quiet operation.
- The fixed capacitor used in PSC motors helps in improving the motor's starting torque and reduces the noise generated during the motor operation.
- In contrast, capacitor-start induction motors or split-phase motors may produce more noise due to the use of additional components like a starting capacitor and a centrifugal switch.

4. Power Factor:
- Power factor is a measure of how effectively a motor utilizes the electrical power supplied to it.
- Permanent split capacitor (PSC) motors generally have a lower power factor compared to capacitor-start induction motors or split-phase motors.
- This is because the fixed capacitor in PSC motors creates a leading power factor, which results in a reactive power component in the motor's current waveform.
- On the other hand, capacitor-start induction motors or split-phase motors may have a better power factor due to the use of additional components that help in improving the power factor.

Conclusion:
In conclusion, a permanent split capacitor (PSC) motor has lower noise compared to capacitor-start induction motors or split-phase motors. However, it has lower efficiency and power factor compared to these motors. On the other hand, PSC motors are generally more cost-effective due to their simpler design. Therefore, the correct answer is option 'C' - noise.