40 Hz tone
Deep sub-bass at the edge of feeling — test what your system does down low.
40 Hz
Stopped
Nearest note: D#1 · 49 cents sharp (38.89 Hz)
What 40 Hz sounds like
Press play and 40 Hz arrives less as a note and more as a pressure wave: a slow, thick throb that you feel in your chest on capable speakers and barely detect on a phone. The closest standard pitch is D#1 at 38.89 Hz, and this tone sits 49 cents sharp of it — nearly a quarter-tone high — so against a bass instrument it sounds distinctly out of tune rather than matched.
That near-miss is normal. The bottom octave of hearing has wide spacing between semitones in hertz but narrow spacing to the ear, so fixed test tones like this one rarely align with played music. Think of 40 Hz as infrastructure sound: the rumble under kick drums, the lowest pipe-organ pedal territory, and the region where home subwoofers prove whether they genuinely reach down or merely claim to on the box.
Putting 40 Hz to work on your system
Run this tone to map your bass response. Play it at a modest level and walk slowly around the room: corners will boom while the middle may nearly vanish, revealing standing waves your room builds at long wavelengths. If the tone is silent on small speakers but appears on headphones, you have found your speakers cutoff point rather than a fault.
Use short bursts instead of long drones, since sustained sub-bass at high level stresses small drivers and tired ears alike. Compare 40 Hz with the 60 Hz tone and the 100 Hz tone to hear the climb from felt pressure into audible bass body and warmth.
More frequencies
Frequently asked questions
Can most speakers play 40 Hz?
Many cannot. Small bookshelf speakers and soundbars typically fade out between 50 and 80 Hz, so 40 Hz may sound faint or vanish entirely. Headphones usually reproduce it, and a dedicated subwoofer should play it firmly. Silence on tiny drivers is a normal physical limit, not a defect.
What note is 40 Hz closest to?
The nearest equal-tempered pitch is D#1 at 38.89 Hz, and 40 Hz sits 49 cents sharp of it — almost a quarter tone high. It falls between D1 and D#1, closer to D#1, which is why it clashes audibly against a bass guitar low E at 41.2 Hz.