Terminal – 1) A point of connection between two wires including a device on the end of a wire or cable that allows attachment and the accepting point on a case of the equipment. 2) A computer keyboard and monitor that allows access and entry of information into or from a computer. 

Terminate - To have an amplifier feed a resistance (usually a resistor) that matches the output impedance of the amplifier. 

Three Way Speaker - A speaker system that has separate speakers to reproduce the bass, mid-range and treble frequencies. 

Threshold of Feeling - The sound pressure level at which people feel discomfort 50 percent of the time. 

Threshold of Hearing - The sound pressure level at which people can hear only 50 percent of the time. 

Threshold of Pain - The sound pressure level at which people feel actual pain 50 percent of the time. 

Throat - The small opening in a horn or in a driver through which the sound pressure wave passes from the driver to the horn. 

Throw - In speakers and in microphones, the amount of movement that the diaphragm can make (without restriction) to produce or pickup the sound wave. 

Tie Lines - Cables with connectors at both ends, usually run through walls or floors, so that a signal can be sent or picked up from some remote location. 

Time Code - Short for SMPTE Time Code (a standardized timing and sync signal specified by the Society of Motion Picture and Television Engineers). 

Time Code Generator - A unit that generates SMPTE time code signals. 

Tone – 1) One of several single-frequency signals at the beginning of a tape reel at the magnetic reference level that will be used to record the program. 2) Any single-frequency signal or sound. 3) The sound quality of an instrument's sound relative to the amount of energy present at different frequencies. 4) In some synthesizers, a term meaning the audio signal that will be put out by the unit which would be similar to the sound of an instrument.  

Tone Arm - The pivoting arm mounted to the base of a turntable to hold the phono cartridge and allow it to advance across the phonograph record during playback.  

Transformer - An electrical device that has two coils that are magnetically coupled. 

Transformer Matrix - A device which uses transformers to take two audio channel inputs and change them to a sum signal (a mix of the signals on the two channels) and a difference signal (the mixture of the two signals with one channel phase reversed so that any signal exactly the same in both channels will be cancelled).

Trap - A filter designed to reject audio signals at certain frequencies

Tube - A shortening of the term Vacuum Tube (an amplifying device that has elements to send and control current through a vacuum in a glass or metal tube). 

Tuned - Regarding a circuit or device, which is most sensitive to a certain frequency. 

Tuned Cavity - A cavity that, because of its physical dimensions, will resonate at a particular frequency (tend to reinforce the energy at certain frequencies of vibration).

Tweak - A slang term for calibration (a setting of all operating controls and adjustments for optimum performance of a device) especially very precise calibration. 

Tweeter - A speaker designed to reproduce the higher frequencies only. 

Unbalanced - A method of interconnecting recorders, amplifiers and other electronic gear using two-conductor cable. 

Uni- - A prefix meaning One.

Vacuum Tube - An amplifying device that is a tube.

Wave - A continuous fluctuation in the amplitude of a quantity with respect to time. 

Wave Velocity - The time it takes for one point of the waveform to travel a certain distance. 

Waveform - The shape made by the fluctuations of a quantity over time. 

Waveshape - The shape made by the fluctuations of a quantity over time. 

Wavelength - The length of one cycle (in feet, inches, etc.)

White Noise - A random energy where there is an energy distribution so that the amount of energy is the same for each cycle, causing the noise level to increase with frequency. 

Wide Band Noise - Noise that has energy over a wide range of frequencies. 

Width - Another term for Depth (the amount of change in the controlled signal by the control signal).