Audio Components

Audio components are a wide variety of devices that are found in audio systems. This includes transducers that convert between acoustical energy and electrical signals. Microphones convert air pressure fluctuations into an electrical signal. Speakers and other output devices convert an electrical signal into a mechanical motion to create sounds. Transducers differ in design and construction depending on the principle of operation employed.
Common types of microphones include: condenser/electrostatic, piezoelectric, moving coil and MEMs. Electrostatic microphones utilize capacitive changes brought about by pressure variation. Piezoelectric microphones utilize the acoustic pressure variation to stress piezoelectric material to create a voltage. MEMs microphones are typically based upon vibration mechanically changing the capacitance of a sensing element. An example of a microphone available in all these types is the ‘Throat Mic’, or Laryngophone. This is a special contact microphone that sits against a wearer’s throat and directly couples speech vibrations and able to work under extreme noise conditions.
Speakers are available in a wide variety of power levels, shapes and types. They are specified by their series impedance that can range from 3Ohms up to over 6kOhms. They are rated for a continuous power level, a maximum power level and a frequency range. The mechanical characteristics impact the linearity of the speaker. Non-linearity produces parametric oscillations and harmonic distortion that reduce the fidelity of the sound conversion. This distortion is usually expressed as a % of power output based upon a sinewave stimulus. Any diaphragm or acoustically vibrating surface will tend to have non-linear areas at its boundaries and in the case of a moving coil, at the extremes of movement. Piezoelectric speakers tend to have poor low frequency performance due to their low air volume displacement.
The directionality of a microphone is a measure of its sensitivity to acoustic signals that it receives from different angles referenced to its central axis. For example, an omnidirectional microphone detects sound from any direction, but a bi-directional microphone is unable to detect sound originating from the sides of its diaphragm. Directional speakers are available that use large arrays of ultrasonic transducers. The transducers pump out modulated frequencies above audio range that demodulate when they hit a solid object (like a person) to produce the original audio. This process is called ‘parametric interaction’ and speakers that work this way are sometimes referred to as parametric speakers. They can work in extremely noisy environments and are available to work over 500m range.