How Tone Generators Work

If you were to ask two different people about tone generators, the likelihood is that you would receive at least two different answers — and any or all of them could be correct. You can find them in multiple disciplines from music to electronic troubleshooting or even pest control. Each application utilizes tone generators differently and sometimes requires different technologies to function. Despite this variance, the basics of all tone generators work on the same principles.

A tone generator, also called a signal generator in some applications, is an electronic device that artificially creates sounds frequencies — usually, but not always by a primarily electrical means. The device creates an electrical signal and converts it into sounds. The sounds a tone generator creates vary depending on the need of the application. Electronic pianos and organs utilize simple tones based upon set frequencies in the musical scale. Electronic devices such as signal testers utilize sounds from simple atonal frequencies to complex assortments of frequencies such as white noise.

The source of the electronic signal for a tone generator varies with the type of application. A classic Hammond organ creates electric signals by sending electric current through vacuum tubes, which cause the current to oscillate. This current is modified by synchronized mechanical elements that keep the signals proportional with one another. In portable testers, the source for the electronic signal is a DC current modified by integrated circuits. Even your personal computer can create tone signals using a digital representation of the sound.

All tone generators convert electrical signals into an audible compression wave in virtually the same way that your home stereo system accomplishes the same task. The electronic signals pass through a coil that produces a magnetic field when it receives a current. The coil is located in proximity to a permanent magnet and connected to a flexible membrane (usually made of paper or plastic). When the electrical signal passes through the coil, the magnetic field changes rapidly, forcing it to be either attracted to or repelled from the fixed magnet, which causes it and the membrane attached to it to vibrate quickly. These vibrations cause compression waves in the air that are known as sound.

You can find tone generators in many applications. Aside from the obvious use in common musical instruments such as organs and pianos, tone generators provide sounds for instruments such as the theremin and create the basis for digital bass and guitar sounds. Cable television companies often use tone generators and electronic induction probes to track down faults in wire shielding. Sound technicians often use tone generators to soundproof rooms used for recording music. Some pest control devices utilize them to create frequencies that repel pests such as mosquitoes and rodents.