It's Author Fun: Audio Terms

As I'm coming to a close on the first draft of my first novella in my first series "White Noise", I'm realizing that my working title (The Tower) is descriptive of a major plot point, but its coming across like a thriller (which its not). The cover too, is coming across like it's a horror film.

Time to re-group the idea. I still like a black on white cover, but maybe I can change the title and image to fall into the Audio Terms I was using for the scene list.

Before

After

Here are some audio terms I found (full list here) that could be used to job my memory.

Terms::

Acoustic suspension - a sealed or closed box speaker enclosure. Also referred to as an infinite baffle. Acoustic suspension speaker systems are generally less efficient than Bass Reflex or Transmission Line designs, but may offer greater accuracy with respect to bass tightness and reproduction.

Acoustics - the science or study of sound.

Alternating (AC) Current - currents that have a harmonic time dependence.

Ampere (A) - the unit of measurement for electrical current in coulombs per second.

Amplifier - an electrical circuit designed to increase the current or voltage of an applied signal.

Amplitude - the relative magnitude of a signal.

Attenuation - the reduction of an electrical signal.

Audio frequency - the acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20 kHz.

Baffle - a board or other planar surface used to mount a loudspeaker.

Bandwidth - the range of frequencies reproduced by an amplifier or transducer.

Capacitor - a charge storage device made up of two metallic plates separated by a dielectric, with equal but opposite charges. The AC impedance of a Capacitor is (1 / jWL) and acts as an open circuit in DC applications.

Circuit - a complete path that allows electrical current from one terminal of a voltage source to the other terminal.

Clipping - a form of distortion caused by cutting off the peaks of audio signals. Clipping usually occurs in the amplifier when it's input signal is too large or when the voltage rails of the power supply cannot deliver the necessary voltage to the power amp.

Crossover Frequency - the frequency at which the driver's roll off at - usually when response is down -3dB. See Roll-off.

Current (I) - the flow of electrical charge measured in amperes.

Decibel (dB) - (1) a logarithmic scale used to denote a change in the relative strength of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. Using the logarithmic relationship for power PdB = 10*log[Pout/Pin] , a doubling of electrical power only yields an increase of +3 dB. Increasing the power tenfold will yield an increase of +10 dB and is a doubling of perceived loudness. The decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2) SPL (sound pressure level) can be measured in dB. 0 dB represents the threashold of normal human hearing, 130 dB represents the threashold for pain, 140 dB causes irreparible hearing damage, and 150 dB can cause instant deafness, anything greater than about 192 dB can kill you.

Diaphragm - the part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of a cone or dome.

Diffusion - The scattering of sound.

Direct Current (DC) - current in only one direction.

Diffraction - a change in the direction of a wave that is caused by the wave moving past or hitting an obstacle.

Dispersion - the spreading of sound waves as it leaves a speaker.

Distortion - any undesirable change or error in the reproduction of sound that alters the original signal.

Driver - a loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet and voice coil.

Dynamic range - the range of sound intensity a system can reproduce without compressing or distorting the signal.

Enclosure - a box that contains the driver(s).

Equalizer - electronic device that acts as active filters used to boost or attenuate certain frequencies. Farad - the basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of charge with one volt across it.

Filter - any electrical circuit or mechanical device that removes or attenuates energy at certain frequencies. See Crossover Network.

Flat Response - the faithful reproduction of an audio signal; specifically, the variations in output level of less than �1 dB which is the threshold of human hearing sensitivity.

Free Air Resonance - the natural resonant frequency of a driver when operating outside an enclosure.

Frequency - the number of waves (or cycles) arriving at or passing a point in one second, expressed in hertz (Hz).

Frequency Response - the frequency range to which a system, or any part of it, can respond.

Group Delay - The group delay of a filter is a measurement of the average delay of the filter as a function of frequency. It is the negative first derivative of a filter's phase response.

Harmonic - the multiple frequencies of a given sound, created by the interaction of signal waveforms.

Harmonic Distortion - harmonics artificially added by an electrical circuit or speaker, and are generally undesirable. It is expressed as a percentage of the original signal. See THD.

Hertz (Hz) - a measurement of the frequency of sound vibration. One hertz is equal to one cycle per second. The hertz is named for H.R. Hertz, a German physicist.

High-pass Filter - an electric circuit that passes high frequencies but blocks low ones by acting as a large impedance to those frequencies. See Band-pass and Low-pass filters.

Hiss - background audio noise that sounds like a Rattler snake. Just hope it is an audio source causing it and not a Rattler snake for your sake!

Hum - audio noise that has a steady low frequency pitch.

Imaging - it is the speakers ability to localize different instruments playing simultaneously. See Soundstage.

Impedance - dependent on frequency, it is the AC equivalent of resistance in a DC circuit.

Inductance (L) - the capability of a coil to store energy in a magnetic field surrounding it. It produces an impedance to an AC current (jwL) and acts as a short circuit to DC. Inductors are commonly used in audio as low pass crossovers. See Le.

Infinite Baffle - a flat surface that completely isolates the back wave of a driver from the front.

Infrasonic (Subsonic) Filter - a filter designed to remove extremely low frequency usually between 8-25Hz or lower, noise from the audio signal. Useful for Ported box designs.

Input - connection from signal source.

Low-Pass Filter - an electric circuit designed to pass only low frequencies and act as a high impedance to frequencies out of the filters passband. See Band-pass and High-pass filters.

Octave - a range of tones where the highest tone occurs at twice the frequency of the lowest tone.

Ohm - a unit of electrical resistance or impedance.

Ohm's Law - a basic law of electric circuits. It states that: the current [I] in amperes in a circuit is equal to the voltage [V] in volts divided by the resistance [R] in ohms; thus, I = V/R.

Out of Phase - when your speakers are mounted in reverse polarity, i.e., one speaker is wired +/+ and -/- from the amp and the other is wired +/- and -/+. Bass response will be very thin due to cancellation.

Phase - Refers to the timing relationship of two or more signals or soundwaves. It's especially important to be sure that your stereo speakers are playing "in phase." This means that the drivers (cones and domes) of your right and left speakers are moving in and out at the same time. If your speakers are "out of phase" you'll hear significantly less bass, and instead of producing a strong center image, the sound tends to stay localized at the speakers.

Phase Coherence - the relationship and timing of sounds that come from different drivers (subs, mids, tweets) mounted in different locations in the vehicle.

Phase Distortion - a type of audible distortion caused by time delay between various parts of the signal; can be caused by equalizers.

Polarity - the orientation of magnetic or electric fields. The polarity of the incoming audio signal determines the direction of movement of the speaker cone. Must be observed when wiring speakers, so that they are "in phase". See Out of Phase.

Resonance - the tendency of an object to vibrate most at a particular frequency.

Resonance Frequency - the frequency at which the speaker tends to vibrate most at a certain frequency.

Resistance (Re) - in electrical or electronic circuits, a characteristic of a material that opposes the flow of electrons. The higher the gauge of wire, the less cross sectional area contributing to DC series resistance (DCR).

Signal-to-noise (S/N) - the ratio, expressed in dB, between the signal and noise.

Sine wave - the waveform of a pure alternating current or voltage. It deviates about a zero point to a positive value and a negative value. Audio signals are sine waves or combinations of sine waves.

Sound Pressure Level (SPL) - the loudness of an acoustic wave stated in dB that is proportional to the logarithm of its intensity.

Standing wave - a buildup of sound level at a particular frequency that is dependent upon the dimensions of a resonant room, car interior, or enclosure. It occurs when the rate of energy loss equals the rate of energy input into the system. This is what you hear when you listen into a sea shell.

Surround (suspension) - the outer suspension of a speaker cone; holds the diaphragm in place but allows it to move when activated. Usually made of foam or rubber.

Timbre - The quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature -- why a trumpet and a saxophone sound different when they play the same note.

Total Harmonic Distortion (THD) - the RMS value of the harmonic components of the output signal, excluding the fundamental, expressed as a percentage of the RMS of the fundamental.

Transient Response - the ability of a speaker to respond to any sudden change in the signal without blurring (smearing) the sound. A speaker that can react quickly to rapid changes in sound has "good transient response".

Treble (highs) - the upper end of the audio spectrum reproduced by tweeters, usually 3 - 4 kHz and up.

Volt (E) - a unit of measurement used to measure how much "pressure" is used to force electricity through a circuit.

Watt - a unit of electrical power. A watt of electrical power is the use of one joule of energy per second. Watts of electrical power equals volts times amperes.

Wavelength - the length of a sound wave in air. It can be found for any frequency by dividing the speed of sound in air (1120 feet per second) by the frequency of the sound, or: WL = 1120 / Freq.