As technology has advanced over the years, so has the way society has viewed its media. In the world of audio and radio communications, “viewers” listen to media rather than watching or reading it. To improve the listener’s ability to hear music, news, talk radio, or other sources of entertainment and communication, noise canceling headphones have been invented. This article will help the reader understand what noise canceling headphones are and how they work by examining some of the basic aspects and types of sounds.
Transverse Waves
Transverse waves are the type of waves that most people are used to seeing. For instance, ocean currents are transverse waves. Transverse waves have crests and troughs, with the crest being the top part of the wave and the trough being the bottom part. A wavelength is the distance between each crest or trough. An amplitude is the height between the crest and the trough. Frequency is measured by how many crests or troughs pass by a specific point in a certain amount of time.
Longitudinal Wave
Longitudinal waves are similar to transverse waves but differ slightly. It is important to know the differences between longitudinal waves and transverse waves because sound only travels in longitudinal waves. Instead of having crests and troughs, longitudinal waves have compressions and rarefaction, with compressions being tight pockets of air molecules and rarefaction being loose, spread out air molecules. Amplitudes, wavelengths, and frequencies still apply in longitudinal waves with the frequency making up the pitch and the amplitude deciding how loud the sound is.
Electrostatic Forces
Electrostatic forces refer to the phenomenon associated with static electricity and electrons in general. When an atom gains electrons, it is negatively charged; when an atom loses electrons, it is positively charged. Opposite charges attract each other while like-charges repel each other. Electrostatic headphones use these forces to create sound. In an electrostatic speaker or a pair of electrostatic headphones, a thin piece of paper or metal (called a diaphragm) is suspended between two electrodes. As electricity is applied to the electrodes, the diaphragm is repelled and attracted to the electrodes in various areas. As the diaphragm moves through the air, it creates sound waves.
Electrodynamic Forces
Electrodynamic forces are similar to electrostatic forces: electrodynamics relies on attraction and repulsion of atoms. Electrodynamics also relies, however, on the fact that when an electric current is passed through a coil, a magnetic field is created. Electrodynamic headphones and speakers use these two principles to create sound. In the device, a voice coil and a permanent magnet are placed on one end of a paper or metal cone that acts as a diaphragm. The voice coil acts like an electromagnet when an electric current is applied to it. Because the voice coil is attached to the cone and the permanent magnet is not, the permanent magnet causes the voice coil to be attracted to and repelled from it. This movement causes the diaphragm to move the air and create sound waves.
Destructive Interference
Destructive interference refers to the way that noise-canceling headphones work. While noise-canceling headphones are packed with a lot more material to block out external noises, they also destructive interference by generating their own noises that are exactly 180 degrees out of phase with the external noises. This cancels out the external noise so that the listener only hears what is coming out of the headphones.
