Module 5 - Electroacoustics

Electroacoustics  ::  Electricity  ::  Filters  ::  Microphones  ::  Recording  ::  High-Fidelity Sound

Recording

The mechanical recording of sound was invented by Thomas Edison in 1877. His idea for it's possibility came while he was trying to invent a better way to record telegraph messages on some form of paper or foil. He noticed when he used the foil that it would create a indentation as the needle moved back and forth. This caused him to wonder if he could have sound waves cause a needle to make different levels of indentation in correlation with the frequency. These indentations would be a "recording" that could be played back. It worked, and thus was born the Edison phonograph.

Vinyl records, popular until CDs came along, used these very same principles for recording and playback. The only difference is that the needle on modern record players move horizontally instead of vertically as they did in Edison's phonograph.

During the web activity of this module, you will have the chance to listen to several examples of early disc recordings.

To successfully complete this chapter you should...

• Read chapter 21 in your text book (pages 419-366).
• Carefully study the important concepts about recording sound as you read the chapter.
• Be able to describe the basic principles of disc recording, and magnetic tape recording.

Important Concepts

Disc recording
Dynamic range
Phonograph pickups
Stereophonic discs

Magnetic tape recording
Tape speed and frequency response
Bias and equalization
Tape noise
Multiple tracks

Digital tape recording