railway RRB JE (CBT I + CBT II) Mock Test 2024 Analog Electronics Power Amplifiers and 555 Timer and Voltage Regulators
In any function where microphone, amplifier and speakers are used often one would hear a humming sound, which increases in volume gradually. This is due to:
1
Positive feedback between microphone and speaker
2
Negative feedback between microphone and speaker
3
Inadequate frequency response of amplifier
4
Noise pickup (50 Hz) from power supply