In contrast, delta rhythms (0.5 Hz–4 Hz) are present during episodes of deep sleep. For example, the neural oscillations of a highly aroused and engaged individual are typically in the gamma band (30 Hz–40 Hz), reflecting neural synchronization. Different psychological states are indicated by how fast these groups of neurons oscillate, also measured as cycles per second (i.e., Hz).

Neural oscillations are rhythmic neural activity that repeat across time, and large numbers of neurons oscillating in synchrony produce oscillatory electric fields that can be measured on the scalp by EEG. When considering the so-called ‘background’ (or ‘spontaneous’) EEG, the collective behavior of groups of interconnected neurons (i.e., neural oscillation) depends on the psychological state of the individual. Since the 1920's it has been known that various psychological states correlate with unique measures of the electroencephalogram (EEG). Beyond explaining the mechanisms at the level of the primary auditory system, some have proposed that binaural beats can influence brain activity via ‘brainwave entrainment’, which refers to the use of rhythmic stimuli to produce a ‘frequency-following’ response in the brain. Research indicates that prior to the two tones arriving at the higher processing regions of the brain (i.e., the auditory cortex) via the thalamus and reticular formations, they are integrated in the superior olivary complexes in the brainstem. The perception of binaural beats results from a superposition of the afferent signals at a neural center connected to the cochlea of each ear. It is this third tone that is the binaural beat, so called because it is perceived as fluctuating or ‘beating’ in the temporal domain, and it is a tone that would not be encountered in the real world, as generally the human auditory system does not respond to tones below 20 Hz. This third illusory tone will be 6 Hz, simply the mathematical difference between the two real tones (i.e., 110 Hz–104 Hz = 6 Hz). However, the listener also perceives a third tone that is not present acoustically – hence the classification of binaural beats as an auditory illusion. For example, presenting a 110 Hz tone to the left ear (the 2nd octave of A (A2) on the piano) and a 104 Hz tone (G#2 on the piano) simultaneously to the right ear elicits sensations of both tones in the listener.

Typically, a binaural beat can be reliably produced by two pure tones both with frequencies lower than 1500 Hz (Hz), and with less than 40 Hz between them. Dichotic listening involves the simultaneous presentation of two different sounds, one to the left ear and one to the right. In psychology a binaural beat is classified as an auditory illusion that can be produced using dichotic listening tests. Commonly, musicians tune instruments by eliminating these acoustic beats. In the acoustic domain monaural beats occur when two acoustic waves of slightly different frequencies are added together, whence the resulting interference pattern creates a pulsating wave that is perceived by an individual as a ‘beating’ sound. The current study focuses on one of these alternative approach to stress reduction, binaural beats, which are being produced digitally by a number of commercial entities as brainwave entrainers that enhance quality of life (e.g., ). Beyond these evidence-based approaches a so-called “self-help” industry has also emerged, marketing numerous alternative approaches to stress reduction without supporting evidence. The clinical management of stress can be approached from different perspectives, for example pharmaceutical or psychological interventions focused on building coping skills and resilience. Because stress is considered an undesirable state that negatively impacts psychological and physical wellbeing, a global industry dedicated to stress reduction has developed. Irrespective of innate personal characteristics or social status, most individuals experience stress on a regular basis. Acute stress may be beneficial in terms of individual performance and survival, but chronic stress is linked to cardiovascular morbidity and mental illness.

Stress describes the internal state of an individual experiencing strain or pressure from external (i.e., stressors) or internal (i.e., negative emotions) events that demand resources beyond the individual's coping capacity.

Binaural beats arousal frequency