Room Acoustic Test — MATT Modes

A room acoustic test plays rapid tone bursts so you can hear your room ring. Bursts repeat 4 to 16 times per second at presets from 60 Hz to 1 kHz, or sweep 28 to 800 Hz in 35 seconds; when the silent gaps between bursts fill in, that frequency is ringing. Everything runs in your browser; nothing is uploaded.

How to use it

1. Choose a mode. Fixed Resonance Presets holds one frequency; the 28 Hz to 800 Hz Sweep makes a full pass. Start with presets so you can repeat a single frequency.
2. Pick a preset. 60, 100, 160, 250, 500, or 1000 Hz. Start at 100 or 160 Hz, where domestic rooms usually ring worst.
3. Set the burst rate. 4, 8, 12, or 16 bursts per second. At the default 8 Hz the cycle is 125 ms: 62.5 ms of tone and 62.5 ms of silence, with a short ramp at each edge so the bursts stay click-free.
4. Press Play Articulation Test and sit in your normal listening position. Listen to the gaps, not to the tone.
5. Compare seats. A mode that rings at one chair can be absent a metre away, so repeat from two or three positions.
6. Sweep to find the transition. The 35 second sweep covers 28 to 800 Hz logarithmically, about 7.2 seconds per octave, with the current frequency on screen. Note where the pulses blur and where they snap back to crisp pips.

What articulation bursts reveal

A steady tone fills a room and hides its own decay. Gating it on and off exposes that decay in the silence: if the room is still ringing when the next burst starts, the gap never goes quiet and the pulses fuse into a continuous drone. That blur is the audible signature of a room mode or a long decay time.

At 8 bursts per second each gap is 62.5 ms long. A resonance that rings for 300 to 800 ms cannot decay inside that gap, so several bursts’ worth of energy overlap and the articulation disappears. Drop to 4 bursts per second and the gap grows to 125 ms, which exposes longer decays; raise the rate to 16 and the gap shrinks to about 31 ms, so only very short decays stay crisp.

Reverberation time is the standard measure of this behaviour: RT60 is the time for the level to fall by 60 dB. ISO 3382-2:2008 specifies measurement methods for reverberation time in ordinary rooms. This page does not measure RT60; it lets you hear the phenomenon, so a burst that stays crisp means the room absorbs that frequency quickly, while a burst that drones means it does not.

A mode changes level as well as decay. At a pressure maximum the frequency sounds loud and rings; at a pressure null it can almost vanish, which is why one bass note can boom while the note a semitone away disappears.

Room modes, decay and the Schroeder frequency

For a rectangular room, axial modes between one pair of walls follow f = n × 343 / (2L). A 5.0 × 4.0 × 2.5 m room has first axial modes at 34.3 Hz, 42.9 Hz, and 68.6 Hz, with tangential and oblique modes filling in above them.

Above a certain frequency modes stop behaving as isolated resonances and start overlapping, which smooths the response. That transition is the Schroeder frequency, f_s ≈ 2000 × √(RT60 / V), with RT60 in seconds and V in cubic metres. A 50 m³ room with a 0.4 s decay gives f_s ≈ 2000 × √(0.008) ≈ 179 Hz. Below it the preset list matters most; above it the sweep checks broadband absorption and reflections.

Treatment follows the same physics. Porous absorbers work where air particles move fastest, a quarter-wavelength away from a hard boundary: at 100 Hz that is 0.86 m, which is why thin foam does not fix bass. Corner placement is standard because pressure peaks at boundaries.

Preset	Wavelength at 343 m/s	What it tends to excite
60 Hz	5.72 m	Lowest axial modes of long room dimensions; the deep drone zone
100 Hz	3.43 m	Sub and kick punch; second-order axial modes
160 Hz	2.14 m	Low-mid boxiness; the chest of a male voice
250 Hz	1.37 m	Warmth and mud; tangential modes start to overlap
500 Hz	0.69 m	Midrange articulation and first reflections

Accuracy, limits and troubleshooting

• This is a listening test, not a measurement. The page has no microphone input and produces no RT60 number; it makes modal ringing audible in a normal room.
• Burst rate sets what you can hear: a long gap exposes long decays, a short gap exposes short ones. If everything sounds blurred at 16 bursts per second, drop to 4 before concluding the room is bad.
• Above the Schroeder frequency the test changes meaning. Once modes overlap, decay is dominated by broadband absorption and the burst method loses its diagnostic edge, which in a typical domestic room happens somewhere between 150 and 300 Hz.
• Speaker and listener position dominate the result. A mode at one seat may be absent at another, so repeat from more than one position and move the speaker before buying treatment.
• Small speakers cannot play the low presets. If 60 Hz is inaudible on a laptop or phone, the test is working; use full-range speakers for the bottom of the list.
• Distortion can masquerade as ringing. A driver straining at high level produces its own blurred texture, so lower the volume and repeat: if the blur stays, it is the room.
• A single reflection can sound hollow rather than ringing. Comb filtering from an asymmetric side wall makes bursts sound doubled or thin, so check channel symmetry with the speaker test first.
• Processing can rewrite the decay. Receiver room correction, night mode, and loudness settings alter level and time behaviour, so disable them while you listen.
• Keep levels modest. Low-frequency bursts work a driver hard even when they do not sound loud, and sustained high-level bass heats voice coils.

Related tools

• Subwoofer Test — Find the room modes this page makes audible with discrete tones and a slow sweep.
• Speaker Test — Check channel symmetry, balance, and polarity before blaming the room.
• Room Modes and Standing Waves — The theory behind the frequencies you hear ringing here.