Research on sound and frequency in humans is busier than on the animal side — and messier. Three separate topics need to be kept apart, because they are constantly used in the same sentence while being very different things.

1. Vibroacoustic application: feeling sound rather than hearing it

Vibroacoustic application means delivering low-frequency sine tones (typically 20–120 Hz) directly into the body through a bed, chair or mat fitted with transducers. The idea is not to hear the sound with your ears but to feel the vibration in tissue. The method was named by Olav Skille in 1980s Norway.

State of the evidence: Small studies exist on fibromyalgia, chronic pain, Parkinson's and agitation in care homes, and some report positive results. But systematic reviews consistently say the same thing: samples are small, protocols differ from one another, blinding is rare and results are not reproducible. That places it in the "promising but unproven" category — which is not the same category as "proven".

Note: This method requires dedicated transducer hardware. Playing 40 Hz through a phone speaker is not vibroacoustic application; a phone speaker cannot produce 40 Hz at meaningful power in the first place.

2. Binaural beats: two ears, two frequencies

The binaural beat is a real and well-defined perceptual phenomenon. Feed 200 Hz to the left ear and 210 Hz to the right, and you perceive a 10 Hz "beat" that is physically present in neither ear. It arises during auditory processing in the brainstem. The phenomenon itself is not in dispute.

What is disputed is whether that beat pulls brainwaves toward its own frequency (entrainment) and whether this produces a useful effect on anxiety, attention or sleep. There is a lot of research and the results are mixed: some meta-analyses report a small effect on anxiety, others find no consistent effect. Effect sizes are generally small and study quality varies.

Critical technical point: Binaural beats require headphones and two different frequencies, one per ear. Played through a speaker, the two tones mix in the air and what you get is not a binaural beat but an ordinary acoustic beat — a different thing.

Rezzonix does not produce binaural beats. The app plays a single tone and does not send different frequencies to the two channels. We make this distinction because it is one of the most common confusions in the field.

3. 40 Hz stimulation: an early but genuine research line

In recent years a notable research line has developed around the effect of 40 Hz light and sound stimulation on gamma-band brain activity. Studies in mouse models reported that 40 Hz stimulation triggers particular cellular responses, and those findings have moved into human trials.

Two things need saying at once here. First: this is real research conducted at serious institutions, not something to be mocked. Second: it is early stage. Human trials are small, results are not yet settled, and no health authority recognises it as an approved treatment. Between a promising research line and a clinically proven one lie years and a great many failed candidates.

Content circulating online in the form of "listen to 40 Hz and repair your brain" skips that distance entirely. The stimulation protocols used in the studies — specific duration, specific schedule, usually with simultaneous light — are also not the same thing as listening to a tone from a phone.

So where does Rezzonix sit?

Rezzonix is not a device for any of these three:

It is not vibroacoustic hardware — there are no transducers, and a phone speaker cannot produce low frequencies.
It does not produce binaural beats — it plays a single tone.
It does not implement a 40 Hz research protocol — it is a catalog and a player.

What the app does is generate your selected frequency as a clean square wave. We claim nothing beyond that, and we wrote this article precisely in order not to make those claims.

If you are going to run your own trial

Being curious and experimenting is legitimate. But if you want to learn something from your trial you need a control, one variable at a time and a measure chosen in advance — we have a separate article on how to do that. And in every case: do not listen loudly, for long periods, through headphones. Hearing loss does not come back.