Questions and Problems

Author: N.H. Crowhurst

1. Why is a microphone needed in an electrical amplifying system, and

what are its two basic actions?

2. What is the essential feature of a dynamic microphone? Indicate which of the following types can be called dynamic: moving-coil, ribbon, condenser, crystal, carbon.

3. Explain the reason for the construction of a moving-coil microphone with special reference to (a) the shape of the magnet, (b) the shape of the coil, (c) the requirements of the diaphragm,

4. All the following designations may correctly be applied to the same microphone; however, some of them may also be applied to other types to which the remaining designations are not applicable; dynamic, ribbon, bidirectional, velocity, pressure gradient; explain these differences.

5. What feature do the ribbon and condenser type microphones share in common? In what respects do they differ?

6. What operation similarity is there between a condenser microphone and a carbon microphone?

7. How does a crystal microphone work, and what steps are taken to make its sensitivity comparable with that of other types?

8. What are the three basic directional characteristics of microphones?

9. What is meant by (a) pressure and (b) velocity microphones? Do these methods of operation have any connection with directional pattern? If so, into which group would you classify a cardioid pattern?

10. If someone asked for a "directional" microphone, what types could be intended? Explain.

11. Give two reasons why the type of microphone used for telephones does not need electrical amplification.

12. Would you expect a small moving-coil loudspeaker to make a good or bad microphone? Explain.

13. Why does any high-quality microphone need amplification?

14. When a ribbon microphone whose resistance is .05 ohm is used with a 500:1 step-up transformer, it produces 500 times the voltage output for a given sound wave. What is the effective resistance of the equivalent microphone with its transformer?