Reverberation time—commonly called RT60—is the length of time it takes for sound to decay by 60 decibels after the source stops producing sound. In practical terms, it measures how “live” or “dead” a room sounds. A room with a short RT60 (under 1 second) absorbs sound quickly and feels dry and controlled. A room with a long RT60 (2–3 seconds or more) bounces sound around, creating a lively or echoey character.
RT60 is the standard metric in acoustics and audio engineering for quantifying the acoustic character of any enclosed space—from a recording studio to a concert hall. Understanding it helps you choose reverb settings in a mix, treat a room for recording, or evaluate whether a space is suitable for recording drums, vocals, or acoustic instruments.
How RT60 Is Measured
Measuring RT60 requires sound level data over time. Ideally, a technician plays a burst of sound (an impulse or swept sine wave) in the space, records the reflections, and graphs the sound pressure level as it decays. The RT60 value is the time between the moment the sound stops and the moment it drops 60dB below its initial level.
In practice, measurement is often done at multiple frequencies because RT60 is frequency-dependent. Low frequencies decay slower than high frequencies in most rooms. A room might have an RT60 of 0.8 seconds at 1kHz (mid-range) but 1.2 seconds at 125Hz (bass). Professional measurements report RT60 across the full frequency spectrum.
For home studios or rough estimates, acoustic software and room acoustic analyzers can estimate RT60 by analyzing impulse responses. These are less precise than lab measurements but useful for identifying problem areas.
The Sabine Formula: Predicting RT60
The Sabine formula is the foundational equation for predicting RT60 in a room before it’s built or treated:
RT60 = 0.161 × (Volume in cubic meters) / (Total absorption in sabins)
In English units: RT60 = 0.049 × (Volume in cubic feet) / (Total absorption)
Here’s how it works:
- Volume is the cubic footage of the room
- Absorption is calculated by multiplying the square footage of each surface by its absorption coefficient at a given frequency, then summing those values
The formula shows that larger rooms have longer RT60s (more space = more reverb), and rooms with more absorptive material have shorter RT60s. It’s a prediction tool; real rooms deviate due to geometry and mode behavior, but Sabine is reliable for initial planning.
Why RT60 Varies by Frequency
Bass frequencies reflect off walls differently than high frequencies. In most rooms, low frequencies (below 200Hz) have a longer RT60 than mids and highs. This is why untreated rooms often sound boomy—bass hangs around for 2–3 seconds while snare cracks disappear in 0.5 seconds.
Professional acoustic treatment accounts for this. Broadband absorbers work across frequencies; bass traps target low-end specifically. A well-treated room has relatively flat RT60 across the frequency spectrum, typically 0.8–1.2 seconds at all frequencies.
To understand how to measure and optimize RT60 in your room, explore the room acoustics guide.
Typical RT60 Values by Room Type
Small bedroom: 0.4–0.8 seconds (very dead, lots of soft furnishings)
Living room or home office: 0.8–1.2 seconds (average)
Untreated basement: 1–2 seconds (hard surfaces, longer decay)
Small recording studio: 0.8–1.2 seconds (goal)
Medium rehearsal room: 1.2–1.8 seconds (still fairly controlled)
Concert hall: 1.8–2.5+ seconds (intentionally live for acoustic instruments)
Bathroom or tile room: 2–3+ seconds (very reflective)
Studio and Mixing Standards
For recording and mixing, the target RT60 is 0.8–1.2 seconds across most frequencies. This range provides enough acoustic detail to capture natural instrument tone while controlling reflections that can muddy recordings. Vocals sound clear, drums don’t get washed in reflections, and the room doesn’t dominate the sound.
Music production styles vary:
- Tight, deader rooms (0.6–0.8s) suit rock and hip-hop, where dry, controlled sound is valued
- Balanced, medium rooms (1–1.2s) suit pop and electronic music
- Livelier rooms (1.5–2s) are sometimes used intentionally for jazz, classical, and singer-songwriter work where acoustic warmth is desired
Relating RT60 to Reverb Settings
When you add reverb to a mix, you’re electronically creating reverberation time that may not exist in your actual recording space. If your voice was recorded in a dead booth (0.5s RT60) and you want it to sound like it was recorded in a concert hall (2.5s RT60), you add a reverb with a 2–2.5 second decay time to simulate that hall.
This is why understanding RT60 is useful when mixing. If your mix sounds too washy and unfocused, the reverb decay is probably too long—lower the reverb time or decay. If everything sounds dry and upfront, add more reverb decay or use a longer reverb time.
Use the RT60 calculator to compute expected decay times and experiment with parameters.
Frequently Asked Questions
What’s the difference between RT60 and early decay time (EDT)?
Early decay time measures how fast the first 10dB of decay occurs. It’s useful because early reflections affect how a space sounds more than the later decay tail. RT60 is the full 60dB decay, which is easier to calculate mathematically.
Why does my untreated room sound bassy?
Low frequencies have longer RT60 values in untreated rooms. Bass reflects off walls and accumulates, creating boom and muddiness. Bass traps and broadband absorption fix this.
Can I achieve a concert hall RT60 in a small bedroom?
Electronically, yes—add reverb with a long decay. Physically, no—you’d need to remove material to make reflections last longer, which is impractical.
What RT60 is best for vocal recording?
0.8–1.2 seconds is ideal. It’s close to the natural acoustics of a professional vocal booth or small studio, keeping the vocal clear and present while sounding natural.