In short, neither is better as they answer different questions. RT60 is the standardised design metric, whereas EDT provides guidance on how humans perceive the acoustics.
RT60 is how long it takes for sound to fully die away in a room after the source stops, while EDT focuses only on the very beginning of that decay — making it much closer to what your ears actually perceive. A room might look identical on paper with the same RT60, but feel completely different to sit in, and that’s where EDT catches the difference. Think of RT60 as the room’s overall personality and EDT as your moment-to-moment experience of being inside it.
| RT60 (Reverberation Time) | EDT (Early Decay Time) | |
| What it measures | Time for sound to decay 60 dB, extrapolated from the later decay curve — typically T20 (−5 to −25 dB) or T30 (−5 to −35 dB) | Derived from the first 10 dB of decay (0 to −10 dB), scaled ×6 to be comparable to RT60 |
| What it indicates | The late, diffuse reverberant field — the room’s overall, statistically averaged decay | Early-arriving energy that dominates perceived reverberance and clarity. |
| Strengths | Standardised (ISO 3382), reproducible; basis for Sabine/Eyring calculations, design targets and code compliance; good for sizing absorption | Correlates far better with the subjective sense of “how reverberant does the space sound”; reveals local, position-dependent problems RT60 averages away |
| Weaknesses | Ignores the first 5 dB, so it can miss what a listener actually perceives in a given seat | More variable; less suited to single-number design targets |
| Best used for | Designing or specifying a room, calculating absorption, checking compliance | Predicting how the space actually sounds, diagnosing clarity/intelligibility and seat-to-seat variation |
Rule of thumb: Use RT60 to design the space, and EDT to judge how it sounds.
In a perfectly diffuse room, the two converge. Where RT60 and EDT diverge, it tells you the late and early sound fields are behaving differently (e.g. strong early reflections, coupled spaces, or uneven diffusion).
