Gamma waves and 40 Hz audio: what the label actually means
“40 Hz” appears frequently in neuroscience discussions and focus-audio marketing. Those contexts should not be collapsed into one claim.
Gamma activity
Gamma refers to relatively fast neural oscillatory activity. Research involving gamma-frequency stimulation is broader than consumer binaural-beat products.
Why 40 Hz appears in audio marketing
Commercial recordings may use or advertise rhythmic stimulation around 40 Hz because of its association with gamma-frequency research. That association does not establish that a particular recording improves cognition.
Consumer rule
Ask two questions: What exactly is the audio doing, and is the cited research actually testing this product and outcome? If not, treat the connection as indirect.