Microphone pick up close and far. How?

Question

Some equipment such as tap recorders, video cameras, other stuff can pick up sounds far away. Other equipment such as public address and other you have to get up close to pick up sounds. How that be possible?

Answer 1

The difference is twofold. One, microphones in video cameras, tape recorders, etc. are omnidirectional. They will record sound from any angle AND the sound is only being recorded or used internally. In the case of a PA (public address) system, the microphones are usually cardioid pattern pickup. Meaning they pick up their sound from a smaller angle. Since they are usually amplifying the sound and sending it out to speakers, they must be used in relatively close range. The reason for this is the sound coming back from those speakers will re-enter the microphone again, is re-amplified and sent out over the system again. This causes what is called a feedback loop that can have very shrill piercing sounds.

Microphone types and placement is a whole topic of discussion in many places. There are many ideas and types of microphones in use. They are engineered with specific purposes in mind. The level of amplification is specific to the particular application for which it is being used.