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Message: [QUOTE="Bombastus, post: 91995, member: 2178"] Across fifty measured living rooms, average reverberation time fell from 0.69 seconds at 125 Hz to 0.40 seconds at 8 kHz. A room can therefore have one quoted RT60 and still decay very differently from bass to treble. RT60 is useful, but the single figure often hides the part you actually hear as tonal character. Low frequencies may hang around after the mids have cleared, while upper frequencies can disappear much earlier because surfaces, furnishings, people, and air do not absorb every band equally. The same idea sits behind [B][URL='https://goldmidi.com/community/resources/reverb-damping-explained.46/']high-frequency absorption in reverb tails[/URL][/B], but room measurements expose the behavior from the other direction. Instead of turning a damping control and hearing the result, you measure how long separate frequency regions take to lose energy. [HEADING=2]Octave-band RT60 reveals the real decay shape[/HEADING] Room-acoustics software commonly reports reverberation time in octave or one-third-octave bands rather than as one broadband trace. Each band gets its own decay curve, so 125 Hz can tell a very different story from 500 Hz, 1 kHz, or 4 kHz. A single published value is often a mid-frequency figure. In practical measurement systems, the 500 Hz and 1 kHz results may be averaged as T Mid, which is useful for comparing spaces but does not describe what the bass or top end is doing. This matters when two rooms carry the same midband RT60. One can have a stubborn 125 Hz tail that makes kick drums and bass notes overlap, while another can lose low-frequency energy quickly and keep a longer upper-mid decay. The headline number matches, but the rooms do not behave alike. The older [B][URL='https://www.sciencedirect.com/science/article/pii/0003682X72900308']domestic-room reverberation measurements[/URL][/B] make the point with actual band data. Average living-room decay shortened steadily across the measured spectrum, while the kitchens in the same survey showed a different frequency profile despite also becoming shorter toward the top end. Reading an RT60 graph by frequency therefore tells you more than asking whether the room is simply live or dead. You can see where decay starts stretching, where it collapses early, and whether the spectral balance changes smoothly or lurches between neighboring bands. [HEADING=2]Low-frequency decay needs a different reading[/HEADING] Bass creates a complication because small rooms stop behaving like a diffuse reverberant field at low frequencies. Individual room modes can dominate instead, producing narrow resonances whose decay depends on frequency, room geometry, source position, and microphone position. A long 63 Hz or 80 Hz tail may therefore be modal ringing rather than a useful broadband RT60 description. Moving the microphone can change the apparent low-frequency decay because a room mode has peaks and nulls in different places, so one measurement position can exaggerate or understate what the room is doing elsewhere. This is where a waterfall plot or spectral-decay view becomes more informative. Instead of reducing bass behavior to one value per band, you can watch narrow frequency ridges persist over time and separate a broad reverberant tail from one resonant note that refuses to die. T20 and T30 add another wrinkle. They estimate a 60 dB reverberation time from shorter measured sections of the decay, which is useful when the noise floor prevents a clean full 60 dB drop, but a crooked or double-sloped decay can make the extrapolated value less representative of what you hear. Small-room bass deserves caution for exactly this reason. If one low-frequency mode rings far longer than its neighbors, averaging it into a neat RT60 number can hide the fault you were trying to identify. [HEADING=2]Frequency-shaped decay changes how reverb feels[/HEADING] Band-dependent decay is not only a measurement issue. Synthetic reverbs deliberately reproduce it because a tail that keeps every frequency alive for the same duration often sounds less convincing than one whose spectrum changes as energy fades. A bright hall can preserve upper frequencies longer, while a softer room can shed them sooner. Low bands can also be shortened to keep the tail from becoming woolly, or extended for weight when the arrangement leaves enough space. When you compare reverb time by frequency, listen for balance rather than chasing a perfectly flat graph. Real rooms are not spectrally uniform, and deliberate variation can sound natural. Trouble starts when one region hangs on so much longer that it masks notes, blurs rhythm, or makes the apparent size of the space change with pitch. For mixing, the useful move is to separate overall decay time from spectral decay. Set the main tail for the musical space you want, then adjust high- or low-frequency decay only where the return overstays its welcome. A four-second reverb does not need every band to remain a four-second reverb. [/QUOTE]

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