The science · Solfeggio
528 Hz, explained
528 Hz is the best known of the nine solfeggio values, often called the love tone. That is its popular name, not a description of an effect. The set was first put forward in the 1970s. In Sonor, 528 Hz is a carrier pitch: it changes the note you hear, not the band.
What the research says
The numbers were derived in the 1970s by Joseph Puleo from a pattern of verse numbers in the Bible's Book of Numbers, and reached a wide audience through the 1999 book Healing Codes for the Biological Apocalypse (Science Feedback, 2022). A popular story says medieval monks sang these pitches. There is no evidence for that. A fact-check found no scientific or clinical evidence that any solfeggio frequency regenerates the body or removes toxins.
DNA repair. No peer-reviewed study was located that tested whether hearing a 528 Hz tone repairs DNA. There is no scientific or clinical evidence that it does.
Akimoto 2018. One study of nine healthy adults is the one most often cited. Akimoto and colleagues played five minutes of soothing piano music, once in standard 440 Hz tuning and once retuned so that a 528 Hz note is in the scale. They tested retuned piano music, not a 528 Hz tone. They measured salivary cortisol and oxytocin before and after each condition. Stress hormone levels were lower after the retuned music and showed no significant change after standard tuning. The comparison was before and after each condition, each against its own baseline. It was not a direct test of one condition against the other. The study has not been repeated, and its authors write that the effects ascribed to the solfeggio frequency have no scientific basis.
Other human studies. Several more recent studies used recordings described as 528 Hz. Each either tested music or chanting rather than a plain tone, compared against silence or no sound, bundled 528 Hz with other differences such as singing bowls, or was observational. In none of them can an effect be attributed to the pitch itself. None tested a pulsing 528 Hz carrier like Sonor's.
Animal studies. Rats exposed to 528 Hz at 100 dB, far louder than background listening, showed changes in brain testosterone and behaviour. Zebrafish embryos exposed to 528 Hz showed no overt malformation. These do not show an effect in listeners.
Overall, the review found no brain response specific to a 528 Hz pitch, and weak evidence for any listener outcome attributable to it.
How Sonor uses it
528 Hz is a named carrier pitch for the isochronic tone. Choosing it changes the note you hear. The pulse rate, and so the band, stays the same. What you hear is a pulsing tone, not music, which matters because the studies above mostly tested music. Sonor applies a loudness correction so 528 Hz is not much louder than the default carrier. See What are carrier frequencies? for what a carrier does.
You can hear Sonor's tones on the listen page.