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Room resonance test: find your room modes with a frequency sweep

Stack 40, 60, 80, and 120 Hz sines and walk the room. Spots where one tone booms and another vanishes are standing-wave modes - move the seat, not the sub.

Room resonance, also called room modes, is the standing wave pattern that forms in any enclosed space at low frequencies. Each room dimension (length, width, height) has a fundamental mode and harmonic modes above it, and they all reinforce or cancel each other depending on where you sit. The cleanest way to find them is to play pure tones across the bass band and walk the room - peaks and dips that sound like a subwoofer problem are actually a seating-position problem.

By TechCompare · Updated

Oscillators
2
2 stacked tones
Frequencies
40 Hz + 60 Hz
Waveform
Sine
Per-oscillator lanes

Calculator

Frequency Generator

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Preset A
4 oscillators - 40 + 60 + (muted) + (muted)
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How this is calculated

The lowest axial mode of a room dimension is at 343 m/s divided by twice the length, so a 5-meter (16-foot) room has its first length mode around 34 Hz. Each dimension generates its own mode ladder, and the combined set of modes is what makes bass response unevenly distributed through the room. Stacking discrete tones at 40, 60, 80, and 120 Hz lets you hear each mode separately instead of being averaged out by a sweep, because a sweep can't isolate a single modal peak from the time it takes to sweep through it. Listen for tones that are louder at one wall and quieter at others - that's a mode you can address by moving your seat or subwoofer.

Verdict

Room modes are a position problem, not a speaker problem. A few minutes with stacked low-frequency tones and a walk around the listening area tells you exactly which frequencies are peaking and dipping where. Move your seat out of a null and your sub out of a corner before you buy a new sub or a DSP unit.

More Frequency Generator scenarios

Subwoofer test
30 Hz
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Headphone rattle
250 Hz
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Hearing test
8 kHz
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Frequently asked questions

What is a room mode?
A room mode is a standing wave that forms at a frequency where the room's dimensions match a multiple of the sound's half-wavelength. At a modal frequency, certain spots in the room have maximum pressure (peaks) while others have minimum pressure (nulls), causing booming or thin bass depending on where you sit.
How do I calculate my room's first mode?
The lowest axial mode of a dimension is 343 m/s divided by twice the dimension's length. A 5-meter room has its first length mode near 34 Hz. Width and height generate their own mode ladders at the same formula.
Should I add bass traps or move my seat?
Move your seat first. Moving out of a null can recover 10 to 15 dB. Bass traps help by reducing the mode's Q, but they need significant depth to work at low frequencies, and they don't fix a bad seating position.

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