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Schumann 4th Harmonic
The pulse here is quick enough to read as a flutter in the tone rather than a beat you could count. Under it sits the same steady low hum as the other Schumann files, one tone to each ear. The fourth resonance itself measures near 27.3 Hz, an electromagnetic mode of the cavity between the Earth and the ionosphere, and nothing a speaker can turn into sound.
Ready to play
Stack this under rain or a fire, keep the blend, and play it with your screen off. Slo, on iOS, Android and Mac.
What the loop contains
A low hum at 217 Hz that never changes level, with no events across the loop and no top end to speak of. The other three Schumann harmonic files here hum within a few hertz of that, so the speed of the flutter is what tells them apart. The 27.3 Hz figure exists only as the gap between the two tones, and at that rate the gap is too fast to hear as separate beats, so it reads as roughness in the sound.
Take the headphones off and most of that goes with them. Both ears then receive both tones, and what is left is the hum.
Where the number comes from
Winfried Otto Schumann predicted these modes in 1952 by treating the space between the ground and the ionosphere as a resonant cavity, and measurement later confirmed him. Lightning powers them, on the order of fifty flashes a second across the planet, so the resonances strengthen and weaken with worldwide thunderstorm activity through the day and across the seasons. The frequencies themselves shift by a few tenths of a hertz as ionospheric conditions change.
A fixed audio file cannot represent any of that. This one plays the same difference tonight as it did last week, whatever the ionosphere is doing. If you came here expecting a live link to the planet, there is not one, and no site offering these tones has one either.
What it is worth listening to
The geophysics is settled and the listening claims are not supported. No clinical guideline or systematic review addresses what happens when a person listens to a tone named after a Schumann mode, and the wider binaural-beat literature is inconclusive, as the Schumann Fundamental page sets out. It is a steady low tone; judge it as one.
If you want a plain pitch instead, the 396 Hz tone and the 174 Hz tone are both single sine waves with no beat in them. The sound library index lists everything, and the Schumann fourth harmonic and brown noise blend in the free sound mixer puts a broadband layer underneath it.
Frequently asked questions
What is the fourth Schumann resonance?
The fourth mode of the cavity between the Earth’s surface and the ionosphere, measured near 27.3 Hz. It is an electromagnetic oscillation, not a sound.
Does this file track the real resonance?
No. It is a fixed recording. The real modes drift by a few tenths of a hertz and vary in strength with global lightning activity; the file does neither.
Can I hear 27.3 Hz?
Not from ordinary speakers or headphones. What you hear is a low hum; the 27.3 Hz figure is the difference between the tone in one ear and the tone in the other.
Is there any proven benefit?
None that holds up. No clinical guideline or systematic review supports the effects claimed for listening to Schumann tones.