Monaural Beats Research Articles

Pentatonic sequences and monaural beats to facilitate relaxation: an EEG study.

In two studies we investigated if specific acoustic stimulations could be more effective to induce a relaxation response in comparison to silence. Acoustic stimulations included monaural beats and musical sequences based on a pentatonic scale. In the first study, 47 participants evaluated monaural beats and pentatonic sequences presented through loudspeakers and varying along three frequencies (0.2, 2, 4 Hz). In the second study, 31 participants relaxed with their eyes closed for 10 min during a passive listening of monaural beats and a pentatonic sequence presented through loudspeakers. A silence condition was introduced as control. All auditory stimuli were designed with a temporal modulation of 0.2 Hz. Concomitant EEG was recorded with a 64-channel system and spectral analysis was performed on delta, theta, alpha, beta, and gamma oscillations to test if each of the three auditory stimulations had a significant effect on EEG spectral power in comparison to silence. In the first study, pentatonic sequences were evaluated as more pleasant and more relaxing than monaural beats. Pleasantness and relaxation were inversely related to frequency. Visual imagery and emotion induction had higher frequency and were rated with a more positive valence in pentatonic sequences than in monaural beats. In the second study monaural beats in comparison to silence strongly decreased beta and gamma oscillations in the first three minutes and strongly increased theta oscillations in the last three minutes. Pentatonic sequences increased delta, theta, and alpha oscillations in the last three minutes while decreasing beta, and gamma oscillations for the whole auditory stimulation. The results show that auditory signals with a very low temporal modulation (0.2 Hz) could be more effective than silence in inducing a relaxation response. Although 0.2 Hz monaural beats were effective in inducing a relaxation response, they tended to be perceived as unpleasant. Pentatonic sequences could be considered as a better alternative to promote relaxation by auditory stimulation.

Influence of monaural auditory stimulation combined with music on brain activity.

Recently, the increasing attention to mental states and psychophysical health has fueled the research into methods that can aid in relaxation and recovery. Traditional methods like meditation and sauna, while effective, have their limitations; thus, the need for more accessible and convenient alternatives. Our innovative approach combines monaural beats with music, attempting to replicate the relaxing effects of a sauna in the auditory domain. In comparison to normal music and silent condition, the power of the theta active band significantly increased when listening to our modified music. Furthermore, after listening to modified music, there was a significant increase in mismatch negativity (MMN) amplitude in the oddball task. Additionally, participants' subjective responses to a questionnaire indicated significant changes in body relaxation and other metrics after listening to the processed music. This state is considered similar to the "totonou" state, which manifests in physical and mental feelings of relaxation, pleasure, and mental clarity in the sauna. Thus, the present research proposes a convenient method for achieving relaxation, opening an avenue for individuals to customize their "totonou" music based on personal preferences.

A pressure therapy method: Monaural beats sonic resonance

A pressure therapy method: Monaural beats sonic resonance

Comparative evaluation of anxiety level during restorative treatment using no music, monaural beats, and binaural auditory beats as audio distraction behavior guidance technique in children aged 6-12 years: A randomized clinical trial.

Binaural auditory beat is an auditory illusion perceived when two different pure-tone sine waves with less than a 30 Hz difference are presented to a listener dichotically. Monaural beat stimulation is achieved by the superposition of amplitude-modulated signals of nearby frequencies to both ears simultaneously. The study aims to evaluate and compare anxiety level during restorative treatment using no music, monaural beats, and binaural auditory beats as audio distraction behavior guidance techniques in children aged 6-12 years. Three-arm, parallel-group randomized study was conducted in the department of pediatric and preventive dentistry. The sample size of 45 participants was calculated and allocated into three groups as no music, monaural beats, and binaural auditory beats group. Teeth with Class I cavity in primary or permanent molars were prepared and restored. Anxiety was measured pre and postintervention using pulse oximeter and Venham's picture test. Data obtained were analyzed with SPSS software version 20.0 and were carried out using one-way analysis of variance and dependent t-test and significance value < 0.05 was considered. Binaural auditory beats and monaural beats showed a better reduction in anxiety levels as per Venham's picture test scores with statistically significant "P" value 0.0001 and 0.064, respectively. Likewise, binaural auditory beats showed better reduction in anxiety levels as per pulse rate scores with statistically significant "P" value 0.0001 as compared to conventional treatment technique. Binaural auditory beat was found to be the most effective followed by the monaural beat compared to the control group. Thus, binaural auditory beats and monaural beats can be used effectively as an essential aid to reduce anxiety in children.

Monotonous sound stimuli embedded with either binaural or monaural beats have the same effect on sleep latency: study on a large subject group

The aim of this study was to test on a large group of subjects the hypothesis that sleep latency (SL) does not depend on the nature of low-frequency beats embedded into monotonous sound stimulus supplied through the fall-asleep process. Specifically, it does not depend on whether those beats are monaural (MB) or binaural (BB). A special application for Android OS was developed and installed on the individual smartphones of 221 subjects for the purpose of the study. Three attempts were performed with each of them using 3 different kinds of monotonous sound supplied according to counterbalanced design. Three kinds of sound were identical in pitch but differed in the beat presence and type: BB, MB or sham (sound without beats). Repeated measures analysis of variance (rANOVA) revealed no significant statistical effect of stimulus type on SL (p=0.21). A pairwise comparison of SL for different stimulation conditions showed the null hypothesis significance level adjusted according to multiple comparison correction to be p=1.0. Thus, in this experiment SL did not significantly depend on the monotonous sound stimulus type: MB, BB, or sham. The software application developed is useful as universal platform to assess at home conditions the impact of various external factors on fall-asleep process.

Modulation of Mind Wandering Using Monaural Beat Stimulation in Subjects With High Trait-Level Mind Wandering.

Mind wandering (MW) refers to a state when attention shifts from the task at hand or current situation toward thoughts, feelings, and imaginations. This state is often accompanied by a decline in mood, and patients suffering from major depression exhibit more perseverative MW. Hence, although the directionality of the relationship between mood and MW is still under investigation, it may be useful to explore possible avenues to reduce MW. In an earlier pilot study, we investigated MW during auditory beat stimulation in healthy subjects using thought-probes during a sustained attention to response task (SART). We found evidence for reduced MW during monaural 5 Hz beats compared to silence, sine tones, and binaural 5 Hz beats. Moreover, the data tentatively suggested that this reduction was particularly pronounced in subjects with high levels of MW during silence. In the current study, we therefore asked whether MW can be reduced by monaural theta beats in subjects with high trait-levels of MW, as indicated by an online MW questionnaire. Preselected subjects performed a SART task with thought-probes assessing the propensity to mind wander, meta-awareness, and the temporal orientation of MW. Stimulation conditions comprised monaural theta beats, as well as silence (headphones on), and sine tones as control conditions. Our main hypothesis stating that the propensity to mind wander during monaural theta beats is reduced compared to both control conditions was only partly confirmed. Indeed, MW was significantly diminished during exposure to the theta beats compared to sine tones. However, reduced MW during theta beats versus silence was only observed in a subgroup using stricter inclusion criteria. Considering possible reasons for this outcome, our data suggest that the preselection procedure was suboptimal and that beat effects are modulated by the individual responses to auditory stimulation in general.

“The most relaxing song in the world”? A comparative study

The objectives of the current study were to obtain four physiological measures sensitive to stress and compare the nature of their decline after a stress task while listening to different sounds. Particular focus was placed on examining the ability of the song “Weightless”, which has been heralded as “the most relaxing song in the world,” to reduce acute stress as measured physiologically. A single-subjects design was deployed with 57 university students acting as participants. Outcome measures were skin conductance, heart rate, respiration rate, and respiration depth that were obtained during a 4-min rest period containing the sound conditions (silence, monaural beats [6 and 16 Hz], aircraft noise,“Weightless”) and referenced to a proceeding stress task. “Weightless” and the 6-Hz monaural beat had significantly lower mean skin conductance than the reference condition (silence), but no differences were noted for rate of decline or final asymptote. Furthermore, after 4 min, “Weightless” was associated with a 36.09% decrease in skin conductance level, favorable to that reported by the song’s creators. In terms of heart rate decline, “Weightless” was no more effective than any other of the sound conditions, while for respiration rate, it was significantly less effective than silence and the 6-Hz monaural beat. Overall, there was evidence that the song “Weightless” was an effective tool to reduce acute stress.

Effects of binaural and monaural beat stimulation on attention and EEG

Nowadays a popular technique to improve mood and cognition is auditory beat stimulation (ABS), which is thought to induce a frequency-following response of brainwaves. The main types of ABS are monaural beats (MB) and binaural beats (BB). BB involves the presentation of a specific frequency to one ear and another frequency to the other ear which may induce neural entrainment. A difference between the frequencies of 40 Hz is assumed to improve cognition. The present study examined the effect of 40 Hz binaural beats (BB) and monaural beats (MB) on attention and electroencephalography (EEG). A total of 25 first-year psychology students (11 males, 14 females) performed a Flanker task while EEG was recorded during the 5 min-presentation of pink noise (PN), MB and BB. With respect to attention, as measured by the Flanker task, the number of false responses in the BB condition was smaller than that in the PN condition while the number of false responses in the MB condition was larger as compared to the PN condition. As there was no association of BB with a consistent increase in absolute 40 or 45 Hz power compared to PN or MB, EEG recordings could not confirm the hypothesized neural entrainment in the brain. Overall, the current findings show that listening to 40 Hz BB improves attention but do not show the occurrence of neural entrainment. Future research is recommended to include a larger sample, to use a broader cognitive test battery and to present auditory beats with a longer duration.

Auditory Beat Stimulation Modulates Memory-Related Single-Neuron Activity in the Human Medial Temporal Lobe

Auditory beats are amplitude-modulated signals (monaural beats) or signals that subjectively cause the perception of an amplitude modulation (binaural beats). We investigated the effects of monaural and binaural 5 Hz beat stimulation on neural activity and memory performance in neurosurgical patients performing an associative recognition task. Previously, we had reported that these beat stimulation conditions modulated memory performance in opposite directions. Here, we analyzed data from a patient subgroup, in which microwires were implanted in the amygdala, hippocampus, entorhinal cortex and parahippocampal cortex. We identified neurons responding with firing rate changes to binaural versus monaural 5 Hz beat stimulation. In these neurons, we correlated the differences in firing rates for binaural versus monaural beats to the memory-related differences for remembered versus forgotten items and associations. In the left hemisphere, we detected statistically significant negative correlations between firing rate differences for binaural versus monaural beats and remembered versus forgotten items/associations. Importantly, such negative correlations were also observed between beat stimulation-related firing rate differences in the pre-stimulus window and memory-related firing rate differences in the post-stimulus windows. In line with concepts of homeostatic plasticity, our findings suggest that beat stimulation is linked to memory performance via shifting baseline firing levels.

Binaural Beats through the Auditory Pathway: From Brainstem to Connectivity Patterns.

Binaural beating is a perceptual auditory illusion occurring when presenting two neighboring frequencies to each ear separately. Several controversial claims have been attributed to binaural beats regarding their ability to entrain human brain activity and mood, in both the scientific literature and the marketing realm. Here, we sought to address those questions in a robust fashion using a single-blind, active-controlled protocol. To do so, we compared the effects of binaural beats with a control beat stimulation (monaural beats, known to entrain brain activity but not mood) across four distinct levels in the human auditory pathway: subcortical and cortical entrainment, scalp-level functional connectivity and self-reports. Both stimuli elicited standard subcortical responses at the pure tone frequencies of the stimulus [i.e., frequency following response (FFR)], and entrained the cortex at the beat frequency [i.e., auditory steady state response (ASSR)]. Furthermore, functional connectivity patterns were modulated differentially by both kinds of stimuli, with binaural beats being the only one eliciting cross-frequency activity. Despite this, we did not find any mood modulation related to our experimental manipulation. Our results provide evidence that binaural beats elicit cross frequency connectivity patterns, but weakly entrain the cortex when compared with monaural beat stimuli. Whether binaural beats have an impact on cognitive performance or other mood measurements remains to be seen and can be further investigated within the proposed methodological framework.

The Effects of Binaural and Monoaural Beat Stimulation on Cognitive Functioning in Subjects with Different Levels of Emotionality.

Today, binaural and monaural beats are offered over the Internet or by mental health institutes to improve wellbeing or cognitive functioning. This improvement is explained by the assumption that the brain adapts its brainwave frequency to the frequency of the auditory beat. The present study examined the effects of binaural and monaural beat stimulation on attention and working memory in high and low emotional participants. A group of 24 participants (16 females, 8 males) between 19 and 31 years old (M = 22.33, SD = 3.42) performed a Flanker task to measure attention and a Klingberg task to measure working memory while listening to white noise (WN), 40 Hz gamma binaural beat (BB) and 40 Hz gamma monaural beat (MB). Speed of performance on all three levels of difficulty of the Flanker attention task was faster under the BB and MB condition than under WN. No differences were found between BB and MB conditions. With respect to the quality of performance on the Flanker attention task and the Klingberg working memory task no significant differences under the WN, MB, and BB condition were found. Finally, as participants with low or high emotionality did not respond differently to BB and MB under any of the conditions, effects of BB and MB seem similar in high and low emotional participants. The present study supports the notion that faster attention processing may equally be attributed to the influence of BB and MB. Further research is recommended to gain more insight in the role of factors such as duration of stimulation of BB and MB, frequency range, most appropriate carrier tones, and the role of personality traits.

Modulation of Mind Wandering Using Auditory Beat Stimulation: a Pilot Study

Mind wandering refers to the process of generating thoughts unassociated with the task at hand or surrounding environment. Previous studies indicate that persistent mind wandering often contributes to negative mood states. Thus, a neuromodulatory technique enabling a reduction in the propensity to mind wander would be desirable. Binaural and monaural beat stimulation is a novel, non-invasive brain stimulation method which has been shown to modify brain activity in regions supposedly involved in mind wandering. In the current study, 40 participants performed a variant of a sustained attention to response task with embedded experience sampling probes, to identify episodes of mind wandering and to assess meta-awareness. During the execution of the task, participants were exposed to binaural and monaural beats at 5 Hz and 40 Hz, in addition to two control conditions (silence (no sound, headphones-only) and pure sine wave at 440 Hz). In the overall group and across all stimulation conditions, we observed no statistically significant modulation of mind wandering. However, a median-split of the data into two subgroups defined by high versus low mind wandering during silence, revealed an effect of stimulation on mind wandering across all conditions in the high mind wandering subgroup, as well as a significantly reduced propensity to mind wander during 5 Hz monaural beats vs. silence. Levels of meta-awareness were unaffected by the stimulation. These findings tentatively suggest that application of auditory beat stimulation may lead to a reduction in levels of mind wandering in subjects who show a greater tendency towards mind wandering.

P 53 Impact of acoustic stimulation on motor response inhibition and error monitoring

Previous studies suggested that acoustic stimulation can be used to modulate cognition, to reduce anxiety level as well as to enhance mood. In this study we investigated whether acoustic stimulation can modulate response inhibition and error monitoring in a continuous performance task. Using the Go-NoGo paradigm in healthy adults during MEG recordings, Mazaheri et al. (2009) was able to predict errors during response inhibition by theta-alpha coupling. Thus, it seems likely that frontal theta activity after an error may boost an adjustment of the mental state of individuals towards more preparatory alertness resulting in alpha decrease and better sustained performance. Here, we investigated whether acoustic stimulation can modulate theta-alpha-coupling and thereby have an effect on error processing. 20 healthy young adults (18–30 years) participated in the crossover study. They ran through four conditions (randomized order): no stimulation, white noise, binaural beats at a frequency of 6 Hz and monaural beats at a frequency of 6 Hz. For all time points first, an EEG recording at rest with eyes closed (“Resting state”-EEG, 5 min) with stimulation (at 3 conditions) was performed. This is followed by an acoustic stimulation simultaneously with the implementation of an inhibition task (Go-NoGo task). Go/NoGo task: Each stimulus (numbers 1–9) was displayed for 0.2 s and the inter-trial interval was 1.5 s. Participants were asked to respond to all digits except of “5” by pressing a button with the right index finger. Digits “1–4” and “6–9” are thus the Go stimuli and digit “5” the NoGo stimulus. Correct Go-trials were categorized as “hits”, correct No-Go-trials as “withholds”, and responses on No-Go as “false alarms”. Stimulation: Acoustic stimulation was performed in different ways. Binaural beats were generated by presenting one ear with a different tone than the other ear. The difference in frequencies, in our case 6 Hz, results in a beating sensation. Whereas the prior superimposition of two tones with different frequencies result in a monaural beat, again at 6 Hz, that is then presented to the subject. Additionally we use white noise and no noise as a control condition. Preliminary behavioral results show a tendency towards improvement of the number of false alarms during the three noise conditions. However, there are no significant findings. Looking at reaction times in false alarms, stimulation conditions have longer reaction times than no stimulation. Especially white noise shows longer reaction times while having the lowest variability in reaction times. Additionally the monaural beat stands out with a very high variability in reaction times. Our behavioral results so far show that acoustic stimulation could have the potential of modulating behavioral responses. So far, white noise seems to be a stimulation that might be able to stabilize performance variability in subjects. As a next step EEG-data as correlates of the behavioral data will be analyzed. These results shall be the basis for further studies, for example, with ADHD subjects.

The Impact of Monaural Beat Stimulation on Anxiety and Cognition.

Application of auditory beat stimulation has been speculated to provide a promising new tool with which to alleviate symptoms of anxiety and to enhance cognition. In spite of reportedly similar EEG effects of binaural and monaural beats, data on behavioral effects of monaural beats are still lacking. Therefore, we examined the impact of monaural beat stimulation on anxiety, mood and memory performance. We aimed to target states related to anxiety levels and general well-being, in addition to long-term and working memory processes, using monaural beats within the range of main cortical rhythms. Theta (6 Hz), alpha (10 Hz) and gamma (40 Hz) beat frequencies, as well as a control stimulus were applied to healthy participants for 5 min. After each stimulation period, participants were asked to evaluate their current mood state and to perform cognitive tasks examining long-term and working memory processes, in addition to a vigilance task. Monaural beat stimulation was found to reduce state anxiety. When evaluating responses for the individual beat frequencies, positive effects on state anxiety were observed for all monaural beat conditions compared to control stimulation. Our results indicate a role for monaural beat stimulation in modulating state anxiety and are in line with previous studies reporting anxiety-reducing effects of auditory beat stimulation.

Comparative analysis of the effect of stimulation with a binaural beat and similar kinds of sounds on the falling asleep process: A brief note

Beats are the physical phenomenon appearing when two oscillation processes of close frequencies are superimposed. In acoustics, there is also the concept of binaural beats, a subjective feeling of the listener when acoustic tones of slightly different frequencies are applied separately to each ear. Commercial products based on the effect of binaural beats enjoy steady popularity in the market of the modern technological tools for psycho- and physiotherapy. In particular, they are applied to improve sleep. But it is the objective evaluation of the physiologic effect of binaural beats on the sleep onset process that has very little evidence for support. This paper provides comparative analysis of the time to fall asleep determined by the onset of the second daytime sleep stage (sleep spindle appearance). The subjects listened to a monotonous sound of three similar kinds: a combination of binaural beats with pink noise, a similar sound with a combination of monaural beats, and a similar sound without any beat. Stimulation by the combination of binaural beats is shown to produce the least sleep onset time as compared to the similar sound containing monaural beats and to the similar sound without beats. Further investigation is required to obtain results that are more consistent.

Binaural beats increase interhemispheric alpha-band coherence between auditory cortices

Binaural beats (BBs) are an auditory illusion occurring when two tones of slightly different frequency are presented separately to each ear. BBs have been suggested to alter physiological and cognitive processes through synchronization of the brain hemispheres. To test this, we recorded electroencephalograms (EEG) at rest and while participants listened to BBs or a monaural control condition during which both tones were presented to both ears. We calculated for each condition the interhemispheric coherence, which expressed the synchrony between neural oscillations of both hemispheres. Compared to monaural beats and resting state, BBs enhanced interhemispheric coherence between the auditory cortices. Beat frequencies in the alpha (10 Hz) and theta (4 Hz) frequency range both increased interhemispheric coherence selectively at alpha frequencies. In a second experiment, we evaluated whether this coherence increase has a behavioral aftereffect on binaural listening. No effects were observed in a dichotic digit task performed immediately after BBs presentation. Our results suggest that BBs enhance alpha-band oscillation synchrony between the auditory cortices during auditory stimulation. This effect seems to reflect binaural integration rather than entrainment.

On the binaural brain entrainment indicating lower heart rate variability

Products based on binaural beat technology are popular as these claim to relax the user by altering (i.e. entraining) the brain's neuronal rhythm and a Google search will result in more than a million hits [ [1] http://www.google.com Google Scholar ]. While this is possible in certain approaches, for example in photic frequency following effects such as in brain–computer interfaces [ [2] Wilson J.J. Palaniappan R. Analogue mouse pointer control via an online steady state visual evoked potential (SSVEP) brain–computer interface. J. Neural Eng. 2011; 8https://doi.org/10.1088/1741-2560/8/2/025026 Crossref Scopus (29) Google Scholar ]; binaural brain entrainment uses two beats (usually sinusoidal tones) that are different in frequency by a small amount that generates a third pseudo-rhythm at the difference of the two frequencies [ [3] Schwarz D.W.F. Taylor P. Human auditory steady state responses to binaural and monaural beats. Clin. Neurophysiol. 2005; 116: 658-668 Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar ]. Furthermore, binaural brain entrainment is also claimed to allow altered states of consciousness and hemispheric synchronisation [ [4] Atwater F.H. Accessing anomalous states of consciousness with a binaural beat technology. J.Sci. Explor. 1997; 11: 263-274 Google Scholar ]. However, the effects of this entrainment on the cardiac rhythm appear to be understudied, though equally important as the effects on the brain. Hence, the investigation here is set out with this aim.

Human auditory steady state responses to binaural and monaural beats

Objective Binaural beat sensations depend upon a central combination of two different temporally encoded tones, separately presented to the two ears. We tested the feasibility to record an auditory steady state evoked response (ASSR) at the binaural beat frequency in order to find a measure for temporal coding of sound in the human EEG. Methods We stimulated each ear with a distinct tone, both differing in frequency by 40 Hz, to record a binaural beat ASSR. As control, we evoked a beat ASSR in response to both tones in the same ear. We band-pass filtered the EEG at 40 Hz, averaged with respect to stimulus onset and compared ASSR amplitudes and phases, extracted from a sinusoidal non-linear regression fit to a 40 Hz period average. Results A 40 Hz binaural beat ASSR was evoked at a low mean stimulus frequency (400 Hz) but became undetectable beyond 3 kHz. Its amplitude was smaller than that of the acoustic beat ASSR, which was evoked at low and high frequencies. Both ASSR types had maxima at fronto-central leads and displayed a fronto-occipital phase delay of several ms. Conclusions The dependence of the 40 Hz binaural beat ASSR on stimuli at low, temporally coded tone frequencies suggests that it may objectively assess temporal sound coding ability. The phase shift across the electrode array is evidence for more than one origin of the 40 Hz oscillations. Significance The binaural beat ASSR is an evoked response, with novel diagnostic potential, to a signal that is not present in the stimulus, but generated within the brain.

Neural sensitivity to periodicity in the inferior colliculus: evidence for the role of cochlear distortions.

Responses of low characteristic-frequency (CF) neurons in the inferior colliculus were obtained to amplitude-modulated (AM) high-frequency tones in which the modulation rate was equal to the neuron's CF. Despite all spectral components lying outside the pure tone-evoked response areas, discharge rates were modulated by the AM signals. Introducing a low-frequency tone (CF - 1 Hz) to the same ear as the AM tones produced a 1-Hz beat in the neural response. Introducing a tone (CF - 1 Hz) to the opposite ear to the AM tone also produced a beat in the neural response, with the beat at the period of the interaural phase difference between the CF - 1 Hz tone in one ear, and the AM rate in the other ear. The monaural and interaural interactions of the AM signals with introduced pure tones suggest that AM tones generate combination tones, (inter-modulation distortion) on the basilar membrane. These interact with low-frequency tones presented to the same ear to produce monaural beats on the basilar membrane, modulating the responses of inferior colliculus (IC) neurons on the 1-Hz period of the monaural beats or interacting binaurally with neural input generated in response to stimulation of the opposite ear. The auditory midbrain appears to show a robust representation of cochlear distortions generated by amplitude-modulated sounds.

Which ear has the asynchronous signal?

Small differences in the frequency of pure tones are heard as changes in loudness, either when the tones are presented within the same ear (monaural beats) or when presented to the separate ears (binaural beats). With complex tones, comparable differences in fundamental frequency (asynchrony) are heard as changes in roughness or musicality. With two fundamental frequencies presented to each ear, a wide combination of monaural and binaural roughness changes are produced. Under conditions where monaural and binaural roughness changes are clearly detected, the identification of which one of the two ears is asynchronous (one ear asynchronous, the other ear synchronous) is at chance. Substantial interaural differences in intensity are required for the successful uncoupling of the asynchronous ear.