Bilateral stimulation (BLS) is most widely recognised within Eye Movement Desensitisation and Reprocessing (EMDR) therapy, where relatively rapid alternating stimulation is used during trauma processing. For a broader explanation of how bilateral stimulation works within EMDR, including the main theoretical models, see this article on how bilateral stimulation works in EMDR. In contrast, slower forms of bilateral auditory stimulation — such as rhythmic left–right panning sounds — are increasingly being used by clinicians as regulation and stabilisation tools.
This blog examines the evidence relating specifically to slow bilateral auditory stimulation used to support nervous system regulation, rather than fast BLS within trauma reprocessing protocols. It is not a comprehensive systematic review. Instead, it presents a focused appraisal of the available research to consider what has been directly studied, what remains theoretical, and where evidence is currently limited.
Historically
In the late 1980s, Francine Shapiro introduced EMDR, a structured psychotherapy approach incorporating bilateral stimulation during trauma processing. Subsequent research established EMDR as an evidence-based treatment for post-traumatic stress disorder (PTSD), with bilateral stimulation forming a core component of the protocol. Laurel Parnell further developed EMDR-informed approaches, particularly in relation to attachment, resourcing, and stabilisation work.
Within contemporary research in EMDR, auditory BLS has been used as one modality alongside eye movements and tactile stimulation. Research into EMDR has primarily focused on relatively rapid bilateral stimulation used during desensitisation phases.
What Do We Know?
A recent electroencephalography (EEG) study (Sudre et al., 2024) examined binaural and spatial auditory stimulation and found these were associated with EEG changes consistent with relaxation, alongside participants reporting increased calm on self-report measures.
However, the study involved a small, non-clinical sample and measured only immediate effects. While these findings are encouraging, they cannot yet be generalised to clinical populations.
A systematic review and meta-analysis (n = 1,436) (Xiong et al., 2025) examined whether binaural beats reduced perioperative anxiety and pain. Across 15 randomised controlled trials (RCTs) binaural beats were associated with reductions in anxiety, systolic blood pressure, heart rate and pain perception.
No adverse effects were reported across the included trials. It is important to note that binaural beats are not the same as alternating bilateral panning sounds. However, this body of research does suggest that structured auditory stimulation can influence autonomic markers and subjective anxiety. Many of the trials were small in scale.
Darota et al. (2020) examined stress responses across visual, auditory, and tactile BLS modalities in a small group of healthy office workers (n = 28). Around 85% of participants showed reduced stress following auditory stimulation. There were no significant differences between stimulation types, suggesting that bilateral input itself may contribute to stress reduction.
Again, this study involved a non-clinical population, low baseline stress levels, and measured only immediate effects.
With a focus on nature sounds, research explored how different natural sounds influenced stress (Fan & Baharum, 2024). This meta‑analysis found listening to nature sounds to be more effective for reducing stress than sitting in a quiet environment. With greater benefits reported for people who were experiencing health conditions or elevated stress levels. Interestingly, some types of natural sounds appeared to be especially helpful. Soundscapes featuring birds, wind, and water were associated with stronger stress-reducing effects, suggesting that richer, more biodiverse audio environments may support deeper relaxation.
The authors highlight high heterogeneity though, and consider this in their limitations and suggest consistency in measures and study designs in future research.
Within EMDR literature, authors such as Shapiro and Parnell describe the use of slower BLS during stabilisation, resourcing, and installation phases. This reflects clinical guidance rather than research trials examining slow BLS as a standalone intervention, but it offers practical guidance for its careful use in therapy.
Clinically informed bilateral auditory resources designed for stabilisation and resourcing can be explored here.
What We Don’t Yet Know?
There is currently no direct empirical research examining slow bilateral nature-based auditory panning as a standalone clinical regulation intervention. Much of the available evidence comes from related areas, including faster BLS using eye movements, auditory and touch for EMDR reprocessing; binaural beat studies; experimental research in non-clinical samples and clinical guidance.
Research examining autonomic regulation during bilateral stimulation has largely occurred within full EMDR protocols or controlled laboratory studies. While some studies have demonstrated physiological changes during trauma processing sessions, there are currently no studies directly measuring heart rate variability or parasympathetic activation during slow bilateral auditory stimulation used as a standalone stabilisation intervention. Evidence for direct nervous system regulation therefore remains indirect and theoretical.
So, what does this mean in practice?
Several mechanisms have been proposed to explain how rhythmic bilateral input may influence arousal and emotional processing. These include dual-attention engagement, rhythmic sensory stimulation, and potential breathing entrainment. However, these mechanisms have not been established for slow auditory stimulation used as a stabilisation intervention.
There are positive findings suggesting that structured auditory stimulation can influence physiological markers of anxiety and stress. Research on natural soundscapes provides additional context for why certain auditory environments may be experienced as calming, although this remains distinct from evidence on bilateral auditory stimulation specifically.
This is not a definitive piece on BLS, but a snapshot of selected research relevant to nervous system regulation. While there is still much to explore in this area, there is emerging evidence suggesting that structured auditory stimulation may positively influence stress and anxiety markers.
Clinical judgment remains central to its use. In clinical practice, slower bilateral auditory input appears most useful during stabilisation phases, particularly when clients benefit from structured support between sessions. In my own work, I use it as an adjunct to therapy, guided by formulation, rather than as a standalone intervention.
For therapists, slow bilateral auditory tools may represent a low-risk, potentially supportive regulation resource when used thoughtfully and within a considered clinical formulation. My intention here is not to overstate the evidence, but to offer a realistic snapshot of what we currently know.
Integrating Slow Bilateral Auditory Stimulation into Practice
In practice, many clients struggle most with maintaining regulation between sessions—particularly following difficult or activating work.
To support this phase of therapy, I’ve developed clinician-designed bilateral audio resources for stabilisation and nervous system regulation between sessions.
• Explore the full audio library → Willow Tree Wellbeing Audio Library
• Or try a short stabilisation audio → Access a Free Stabilisation Audio Sample
Donna Dickinson is a CBT and EMDR-trained psychotherapist with over 19 years’ NHS experience in trauma-focused work. Her clinical interests include nervous system regulation and stabilisation approaches in therapy.
References
Darota, D., Kamińska-Merecz-Kot, D., Smółka, K., Zwoliński, G., & Anbarjafari, G. (2020). Stress reduction using bilateral stimulation in virtual reality relaxation training. IEEE Access, 8, 200351-200366.
Fan, L., & Baharum, M. R. (2024). The effect of exposure to natural sounds on stress reduction: A systematic review and meta-analysis. Stress, 27(1), 2402519.
Parnell, L. (2013). Attachment-Focused EMDR: Healing Relational Trauma. Norton.
Shapiro, F. (2018). Eye Movement Desensitization and Reprocessing (EMDR) Therapy: Basic Principles, Protocols, and Procedures (3rd ed.). Guilford Press.
Sudre, S., et al. (2024). A new perspective on binaural beats: Investigating the effects of spatially moving sounds on human mental states. PLOS ONE, 19(7), e0306427.
Xiong, J., Jiang, X., Cai, B., & Zhao, L. (2025). Binaural beats for perioperative anxiety and pain: A systematic review and meta-analysis. Complementary Therapies in Medicine, 95:103299.