RT60 and Reverberation

What is RT60?

RT60 is the time it takes for sound to decay by 60 decibels after the source stops. It's the industry-standard metric for describing how "live" or "dead" a room sounds.

A room with a long RT60 has lots of reflective surfaces—think of a cathedral or gymnasium. A room with short RT60 has absorptive surfaces—like a recording studio vocal booth or a room with heavy carpeting and curtains.

Graph showing sound decay over time with RT60 marked

RT60 measures the time for sound to decay 60 dB from its initial level

How RT60 is Measured

Sounn measures RT60 during the measurement process. When the MLS test signal plays, Sounn captures the impulse response—the room's acoustic "fingerprint." From this impulse response, RT60 can be calculated.

In practice, measuring a full 60 dB decay requires very loud test signals. Most measurement systems (including Sounn) use:

T20: Time for 20 dB decay, extrapolated to 60 dB
T30: Time for 30 dB decay, extrapolated to 60 dB

Sounn's RT60 Display

After measurement, check the "Room Analysis" section to see your room's RT60 across different frequency bands.

Ideal RT60 Values

The optimal RT60 depends on room size and intended use:

Room Type	Ideal RT60	Notes
Home listening room	0.3-0.5 s	Balanced, natural sound
Recording studio control room	0.2-0.4 s	Critical listening accuracy
Home theater	0.3-0.5 s	Clear dialogue, immersive effects
Vocal booth	0.1-0.2 s	Extremely dry for recording
Concert hall	1.5-2.5 s	Orchestral music benefits from reverb

Home Listening Rooms

Most home listening rooms benefit from RT60 between 0.3-0.5 seconds. Longer than 0.5s often sounds too echoey; shorter than 0.3s can sound unnaturally dead.

Frequency-Dependent RT60

RT60 often varies with frequency. Common patterns in untreated rooms:

Long bass RT60: Low frequencies decay slowly because most room materials don't absorb bass well
Short treble RT60: High frequencies are absorbed by soft furnishings, carpets, and air itself

This imbalance makes bass sound boomy and muddy while treble sounds clear. The ideal is relatively flat RT60 across frequencies.

Graph showing RT60 varying by frequency

Typical untreated room: long bass RT60, short treble RT60

What Sounn Can (and Can't) Do

Sounn can correct the frequency response at your listening position, but it cannot change the room's reverberant characteristics. If your room has a 2-second bass RT60, that reverb will still be present—correction just ensures the direct sound from your speakers is accurate.

For optimal results, combine digital correction with physical treatment (bass traps, absorption panels) to address both frequency response and reverb time.

Improving Your Room's RT60

Reducing RT60 (Adding Absorption)

Bass traps: Place in corners to reduce bass RT60
Broadband absorbers: 2-4" thick panels on walls reduce mid/high RT60
Soft furnishings: Rugs, couches, and curtains absorb high frequencies

Increasing RT60 (Adding Diffusion/Reflection)

If your room sounds too dead (RT60 below 0.3s), consider:

Diffusers: Scatter sound instead of absorbing it
Hard surfaces: Replace heavy curtains with blinds, carpet with hard flooring

Balance is Key

Over-treating a room can make it sound lifeless and fatiguing. A completely dead room is as problematic as an overly reverberant one. Aim for balanced absorption that maintains natural ambience.