How Does Audio Tape Work?

Introduction

The modern-day audiocassette tape was invented in 1963. The portability, ease of playback and ability to instantaneously record audio was a giant leap forward for the home-recording and commercial music industries. However, the technology behind the cassette tape was actually invented in Germany way back in 1928. This technology, known as magnetic tape, is the key to the cassette's success, and has proven to be a remarkably simple, yet effective, way to record audio.

How It Works

The magnetic tape found within a cassette casing is coated in a layer of ferric oxide powder. Ferric oxide benefits from a feature known as ferromagnetism, which results in a permanent magnetic imprint following exposure to a magnetic field. Transforming audio sound into an electromagnetic field and applying it to the magnetic tape can exploit this feature. This is done through the use of an audio recorder, which houses a small electromagnet. This electromagnet is essentially an iron core wrapped in wire. During recording, this electromagnet is is depressed against a small point of the tape. As the cassette plays (and the tape moves along the recorder's head), the electromagnet transfers the unique electromagnetic footprint of the audio to the magnetic tape. When playback is desired, the head of the recorder reads the magnetized data and transfers it to audio speakers.

Creating New Recordings

One of the key benefits of audio tape is the ability to overwrite previous data with new audio. This is possible because the electromagnetism of magnetic tape can be easily altered. The simple introduction of the tape to a new magnetic field causes the unique magnetic imprint of the tape to change. This can be repeated dozens of times, although audio quality will eventually deteriorate as the ferric-oxide powder begins to degrade over time.