Response Times

All speed menus at a glance

Every user-facing control that offers Fast / Normal / Slow (or similar) presets:

Two layers on the spectrum

Before the tables: the analyzer draws two independent level traces when Peak Hold is enabled:

Peak Hold also affects IN/OUT level meter peak ticks and numeric peak readouts. Those use the same Peak Hold Response menu (hold time before fall), not Release Time.

What applies in Average vs Peak

Settings → Spectrum Level chooses how each new FFT frame is turned into the live trace. It does not change phosphor (goniometer only).

Attack Time

Settings → Attack Time · Average spectrum level only

Controls how quickly the live spectrum trace rises when level increases at a frequency. Implemented as an exponential time constant τ (see Under the hood).

In Peak spectrum level, the live trace snaps upward immediately on each hop; only Release Time smooths downward movement (reduces Hann-window sidelobe flutter). The Attack menu choice is kept in state (so it returns when you switch back to Average) but ballistics force instant attack — changing Attack in Average then switching to Peak does not apply that Attack in Peak.

Release Time

Settings → Release Time · active in both Average and Peak spectrum level

Controls how quickly the live spectrum trace falls when level decreases. Same menu, same τ values in both modes — only the direction differs (Peak ignores attack, not release).

Tip. Release Time does not control the white Peak Hold overlay. That uses Peak Hold Response below.

Peak Hold Response

Settings → Peak Hold Response · enabled when Peak Hold is on (root analyzer menu)

After a new peak is captured, the white hold markers (and level-meter peak ticks) stay frozen at that peak for the selected hold time — then fall at a fixed rate. This is not the drop speed; it is how long the marker remains at the peak before it starts falling.

After the hold expires, markers fall at a fixed 20 dB/s on the spectrum (and a matching fixed step on level-meter ticks). Choose Infinite Hold in the root menu to keep peaks frozen until Reset Peak Hold or a metering reset.

Disabled in Spectrogram display mode (menu entry greyed out).

Level meter peak ticks

The same Peak Hold Response hold times apply to the white peak tick on IN/OUT level meters and to the numeric peak readouts. After hold expires, meter ticks fall at a fixed linear step per UI refresh (not tied to the menu selection).

Phosphor Decay

Goniometer right-click → Settings → Phosphor Decay

Controls how many history frames are blended into the cyan phosphor trail on vector goniometer modes (Lissajous, M/S, Polar, Dot, X/Y). Phosphor is always on. Greyed out in Balance-O-Meter mode (no phosphor trail there).

Duration ≈ frames × 512 ÷ sample rate (each goniometer frame is a 512-sample buffer).

Phosphor Decay is independent of spectrum Average / Peak level and from analyzer Attack / Release / Peak Hold Response.

Balance Response (Balance-O-Meter)

Goniometer right-click → Mode → Balance-O-Meter, then Settings → Balance Response

Smooths how quickly the RMS balance triangle widens, narrows, or returns to the centre (mono line) when stereo balance changes. Each update uses one 512-sample goniometer frame (see frame period below — typically ~11 ms at common project rates).

The triangle apex stays fixed at M (Mid). The base expands toward L / R for stereo width and pan — Balance Response only controls how fast that shape moves, not the underlying RMS math.

Menu is greyed out unless display mode is Balance-O-Meter. Phosphor Decay is greyed out in that mode (no phosphor trail on the triangle).

Smoothing per frame: smoothed += coeff × (target − smoothed) where coeff is the rise or fall value depending on whether the triangle is expanding or contracting. Approximate τ values use τ = −1 ÷ ln(1 − coeff) frame periods × 512 ÷ sample rate.

Under the hood

FFT hop period (spectrum)

Attack and Release are applied once per FFT hop, not per audio sample. Hop length depends on FFT size and overlap:

hop period = FFT size ÷ overlap ÷ sample rate

Factory default. FFT 8192 with 8× overlap (analyzer right-click Settings) → hop = 1024 samples → ~21.3 ms @ 48 kHz · ~23.2 ms @ 44.1 kHz. That is why Release → Very Fast (5 ms τ) snaps on the first hop at default settings — one update step is already longer than τ.

Larger FFT sizes use higher overlap so the hop stays ~21 ms at 48 kHz — finer frequency resolution without proportionally slower display updates.

Live trace ballistics (exponential)

Each frequency bin, each hop:

• If the new level is higher than the previous smoothed value → use Attack τ (Average mode only; Peak uses instant rise).
• If the new level is lower → use Release τ.

Smoothing formula (per bin):

smoothed = coeff × previous + (1 − coeff) × new
coeff = exp(−hop period ÷ τ)

τ is the Attack or Release time constant from the tables above. This is a standard hop-synchronous envelope follower on the dB trace.

Peak Hold (hold, then linear dB fall)

When a new peak arrives, the hold marker freezes for the selected Peak Hold Response duration. While the hold timer is running it does not fall. After the timer expires (and while the live level stays below the held peak):

ΔdB = 20 dB/s × hop period

per spectrum update (or a fixed step per UI tick on level meters). It never rises except when a new higher peak arrives (which also restarts the hold timer).

Goniometer frame period

Phosphor Decay and Balance Response advance once per goniometer audio buffer. The buffer is always 512 samples, so the frame period depends only on your project sample rate:

frame period = 512 ÷ sample rate

Supported rates. Axis Utility is designed for 44.1–192 kHz (Specifications). The formula works at any rate in that range — we list common project rates above. Phosphor trail duration ≈ frames × frame period; Balance Response τ values scale the same way.

Peak vs Average measurement

Quick reference (defaults)