Audio Engineering: From Sound to Finished Mix

Frequency

The number of wave cycles per second, measured in hertz (Hz). It strongly relates to perceived pitch.

Wavelength

The distance occupied by one complete wave cycle. At a fixed sound speed, lower frequencies have longer wavelengths.

Amplitude

The size of a wave's variation. In air, greater amplitude corresponds to greater sound-pressure variation.

dB SPL

A logarithmic measure of sound-pressure level relative to 20 micropascals in air.

Phase

The relative position of a wave within its cycle compared with a reference wave.

Polarity

The direction or sign of an audio signal. Inverting polarity flips the waveform vertically.

Input

A point where a device, bus, or track receives an audio signal.

Output

A point where a device, bus, or track sends audio to its next destination.

Insert

A processor placed directly in a channel's main signal path, so the full signal passes through it.

Send

A control that routes a copy of a channel's signal to another destination, often an aux effect bus.

Bus

A shared audio pathway used to combine, route, process, or distribute one or more signals.

Aux Return

A channel that receives audio from an auxiliary bus, commonly an effect such as reverb or delay.

High-pass filter

A filter that attenuates frequencies below a selected cutoff while allowing higher frequencies to pass. Commonly used to reduce rumble.

Low-pass filter

A filter that attenuates frequencies above a selected cutoff while allowing lower frequencies to pass. Useful for reducing fizz, hiss, or excessive brightness.

Bell filter

An EQ shape that boosts or cuts around a center frequency. Its Q control determines the width of the affected region.

Shelf filter

An EQ shape that boosts or cuts a broad range above a high-shelf frequency or below a low-shelf frequency.

Q

A control for filter bandwidth. Higher Q means a narrower bell or notch; lower Q means a wider, gentler curve.

Slope

The rate at which a high-pass or low-pass filter attenuates beyond its cutoff, commonly measured in dB per octave.

Threshold

The level at which a dynamics processor begins acting. In a compressor, audio above threshold is reduced.

Ratio

The amount of level change after threshold is crossed. A 4:1 compressor turns 4 dB above threshold into about 1 dB above threshold.

Attack

How quickly processing begins after the threshold is crossed. Fast attack catches transients; slower attack can preserve punch.

Release

How quickly processing stops after the signal falls below threshold. Poor release timing can cause pumping or prolonged gain reduction.

Knee

How abruptly compression starts around threshold. Soft knee is gradual; hard knee is more abrupt.

Limiter

A compressor with a very high ratio used to contain peaks below a set ceiling.

Pre-delay

The time between a dry sound and the start of its reverb. It can preserve clarity and make the source feel forward.

Decay time

The time a reverb tail takes to fade away. Longer decay generally suggests a larger or more sustained space.

Feedback

The amount of delayed output fed back into the delay input. More feedback produces more repeats.

Chorus

A modulation effect that mixes subtly changing delayed copies with the dry signal, creating thickness and width.

Flanging

A short, changing delay effect, often with feedback, that creates a strong sweeping comb-filter sound.

Auxiliary send

A routing control that sends some of a track to a separate effect return, allowing shared processing and independent wet-level control.

Channel strip

A set of controls for one signal path, typically including input, processing, sends, pan, routing, and fader.

Insert

A processing point placed directly in a channel's signal path, such as an EQ or compressor plug-in.

Send

A copy of some channel signal routed to another destination, often a reverb, delay, or headphone mix.

Bus

A routing path that carries one or more audio signals to another destination, such as a submix or effects return.

Submix

The combined output of related tracks, such as drums feeding a Drum Bus.

Clip gain

A level adjustment applied to an audio clip or region before the channel fader and most channel plug-in processing.

Phantom center

The perceived center location created when similar signals reach the left and right speakers at equal level and nearly the same time.

Pan law

A level compensation rule used by a DAW or console as a signal moves across the stereo field, helping avoid an unintended loudness change at center.

Mono compatibility

How well a stereo mix retains its balance, tone, and essential musical information when left and right channels are summed to mono.

Comb filtering

A pattern of frequency boosts and cancellations caused when a signal combines with a delayed version of itself.

Polarity inversion

Flipping a waveform's positive and negative orientation. Identical opposite-polarity signals can cancel strongly when summed.

Mid-side (M/S)

A stereo representation with Mid as common left-right information and Side as the difference between left and right information.

Early reflection

A sound bounce from a nearby surface that arrives shortly after direct sound and can alter tone or stereo imaging.

Comb filtering

A pattern of frequency boosts and cuts created when similar signals arrive at slightly different times and combine.

Room mode

A low-frequency standing-wave pattern in a room that causes bass buildup or cancellation at different positions.

Nearfield monitor

A studio speaker intended for close listening, where direct sound is relatively stronger than room reflections.

Bass management

The routing and crossover integration of low frequencies between main monitors and a subwoofer.

Reference track

A familiar, professionally finished recording used to understand how known audio behaves on your listening system.

Static balance

The initial relationship of track levels, pan positions, clip gain, and routing before detailed automation. It tests whether the arrangement works at its foundation.

Headroom

The available level space before digital full scale (`0 dBFS`). Headroom helps prevent clipping and leaves room for later processing or mastering.

Mix bus

The main stereo path receiving the combined mix before export. Processing here affects the entire mix and should be used deliberately.

Level matching

Comparing processed and unprocessed signals at similar perceived loudness so that louder is not mistaken for better.

Automation

Time-based changes to parameters such as level, pan, send amount, mute, or plugin controls. It creates intentional movement across the song.

Mono compatibility

How reliably a stereo mix translates when left and right channels are combined. It is checked by monitoring in mono and listening for losses or tonal changes.