Levels & Loudness / Audio Reference

01 / WAVE

The Waveformraw sound, before any meter

Amplitude

Size of the pressure swing. Heard as loudness. Quoted peak, peak-to-peak, or RMS.

sine RMS = peak / √2

Frequency f

Cycles per second. Heard as pitch. A4 = 440 Hz.

f = 1 / T

Period T

Time for one cycle. 1 kHz = 1 ms.

T = 1 / f

Wavelength λ

Length of one cycle in air. c = 343 m/s at 20°C. 100 Hz ≈ 3.4 m.

λ = c / f

Phase °

180° apart cancels; in phase sums +6 dB.

180° = cancel

Crest Factor

Gap between peak and RMS. Low = dense, high = dynamic.

peak − RMS (dB)

02 / LOG

The Decibela ratio, until you name the reference

Power & Intensity

Power, energy, intensity use a factor of ten.

dB = 10 · log₁₀(P/P₀)

Amplitude & Voltage

Amplitude, voltage, pressure use twenty. Power goes as amplitude².

dB = 20 · log₁₀(A/A₀)

+3 dB

Double the power.

×2 power

+6 dB

Double the amplitude. One extra bit.

×2 level

+10 dB

About twice as loud to the ear.

×2 perceived

−6 dB / +1 dB

−6 dB halves amplitude. +1 dB ≈ smallest audible step.

6.02 dB / bit

03 / ZERO

Reference Scalesevery dB scale hangs off a different zero

dBFS digital

0 = the ceiling. Everything below is negative. Cross it, you clip.

0 = full scale

dBTP true peak

dBFS oversampled to catch inter-sample peaks.

ceiling -1 dBTP

dBu analog

0 dBu = 0.775 Vrms. Pro line level, +4 dBu nominal.

0 dBu = 0.775 V

dBV analog

0 dBV = 1 Vrms. Consumer gear, -10 dBV nominal.

0 dBV ≈ +2.2 dBu

dB SPL acoustic

0 = 20 µPa, threshold of hearing. The scale ears feel.

0 = 20 µPa

VU alignment

0 VU aligns to -18 dBFS (EBU) or -20 (SMPTE).

0 VU = -18 dBFS

04 / BS.1770

LUFS & Meteringloudness the way the ear weighs it

LUFS = LKFS

Loudness vs Full Scale. ITU-R BS.1770, K-weighted. The two names are identical.

1 LU = 1 dB

Integrated I

Gated average over the whole program. The number platforms read.

the target

Short-term S

Sliding 3 second window.

3 s

Momentary M

Sliding 400 ms window.

400 ms

LRA range

Spread of quiet to loud, in LU. Low = dense, high = dynamic.

measured in LU

Why not RMS

K-weighting + gating track perceived loudness; flat RMS does not.

K-weighted

05 / DELIVERY

Loudness Targetsintegrated LUFS platforms normalize toward

Destination	Integrated	True Peak	Notes
Spotify	-14 LUFS	-1 dBTP	user -19 / -11 modes; -2 dBTP if above -14
Apple Music	-16 LUFS	-1 dBTP	Sound Check
YouTube	-14 LUFS	-1 dBTP	turns down, never up
Tidal	-14 LUFS	-1 dBTP
Amazon Music	-14 LUFS	-1 dBTP	sometimes cited -13
Deezer	-15 LUFS	-1 dBTP
SoundCloud	~ -14 LUFS	-1 dBTP	varies by player
Apple Podcasts	-16 LUFS	-1 dBTP	-19 for mono
EBU R128	-23 LUFS	-1 dBTP	EU broadcast, ±0.5 LU
ATSC A/85	-24 LKFS	-2 dBTP	US broadcast, CALM Act
Club / loud	-8 to -10	-1 dBTP	streaming turns it down

Universal master: near -14 LUFS with a -1 dBTP ceiling translates safely everywhere. A hotter number just gets turned down at playback, so mix for dynamics and let normalization do the rest.

06 / MATH

Conversionsnumbers worth memorizing

Bit Depth → Range

16-bit ≈ 96 dB, 24-bit ≈ 144 dB.

6.02 N + 1.76 dB

Rate → Bandwidth

Capture up to half the rate. 44.1k → 22.05k.

f max = SR / 2

Ratio → dB

Amplitude: ×2 = +6, ×10 = +20, ×√2 = +3. Power halves those.

20·log = amplitude

Distance → SPL

−6 dB per doubling of distance (free field).

−6 dB / 2× dist

Peak vs RMS

A sine sits 3.01 dB under peak. Real material peaks harder.

RMS = peak − 3.01

dBFS ≠ SPL

Maps to real loudness only after monitor calibration.

calibrate the room

06b / SPL

SPL LandmarksdB SPL in the wild

0 dBThreshold of hearing

30 dBQuiet room, close whisper

60 dBConversation

85 dBRisk over 8 hours (OSHA / NIOSH)

100 dBLoud club, risk in ~15 min

120 dBThreshold of pain

130+ dBJet up close, instant damage