The Safe and Sound Protocol, usually called the SSP, is a listening-based intervention developed by Dr. Stephen Porges and distributed by Unyte Health. It uses specially filtered music and is intended to support nervous-system regulation, auditory processing and social engagement.
Research into the SSP is still developing, but “developing” does not mean nonexistent or invalid. The evidence includes controlled research on the SSP’s precursor, prospective studies, pilot studies, case reports and a growing body of real-world outcome data.
Across these different forms of research, the findings are encouraging.
Improvements have been reported in auditory sensitivity, sensory processing, emotional regulation, anxiety, mood, social engagement and other areas of daily functioning.
At the same time, the research cannot yet tell us exactly who will benefit, which outcomes are most likely or how long changes will last.
The fairest summary is:
The SSP is a promising, research-informed intervention with positive early findings and a growing evidence base. Larger and more independent studies can help us understand how to use it most effectively.
The SSP is a structured listening program based on Polyvagal Theory, a framework developed by Dr. Porges to describe relationships among autonomic state, perceived safety, defensive responses and social engagement.
The music used in the SSP has been altered to emphasize and progressively vary acoustic frequencies associated with the human voice. According to its proposed model, this provides an exercise for auditory pathways involved in distinguishing speech from background noise while presenting the nervous system with repeated cues associated with safety.
The SSP is intended to help create a more regulated physiological state.
This may make it easier for a person to:
This is why SSP is generally described as a “bottom-up” intervention. Instead of beginning with conscious thought or behavioural strategies, it begins with patterned sensory input intended to influence the person’s physiological state. SSP is designed to support vagal and autonomic regulation.
Research has examined both the current SSP and an earlier version called the Listening Project Protocol, or LPP.
The LPP is the direct research precursor to SSP, so its findings are relevant to the development of the intervention. However, it is worth identifying it accurately rather than assuming that every aspect of the earlier research protocol is identical to current clinical delivery.
The strongest controlled findings come from two randomized trials involving a combined 146 autistic children and young people.
In the first trial, filtered music was compared with wearing headphones without music. In the second, it was compared with listening to unfiltered music. The studies reported that the filtered intervention selectively reduced auditory hypersensitivity. Improvements were also reported in areas including listening, spontaneous speech, behavioural organization and emotional control, although not every outcome improved in every comparison.
These trials were published as Reducing Auditory Hypersensitivities in Autistic Spectrum Disorder: Preliminary Findings Evaluating the Listening Project Protocol.
An earlier study also examined auditory processing and autonomic regulation in autistic children and young people.
Following the intervention, participants showed improvement on standardized tasks that required them to understand speech presented with competing speech or background sound.
Changes in respiratory sinus arrhythmia, a component of heart-rate variability, were also investigated.
That study can be read here: Respiratory Sinus Arrhythmia and Auditory Processing in Autism: Modifiable Deficits of an Integrated Social Engagement System?
Together, these studies provide encouraging evidence that the intervention may influence auditory sensitivity and the ability to process human speech in challenging listening environments.
A 2023 prospective study followed 37 autistic participants who completed the SSP in home, school or clinical settings.
At the one- and four-week follow-ups, participants or caregivers reported reductions in auditory hypersensitivity, reduced responsiveness to voices, visual sensitivity and digestive difficulties. Tactile sensitivity and selective eating also decreased at the four-week follow-up.
At four weeks, 70.3% of participants had shown at least a 30% change in one measured area. Reported effect sizes were generally small to moderate.
This study is particularly useful because it examined SSP in the settings where it is commonly delivered.
Read the full study: Effects of the Safe and Sound Protocol on Sensory Processing, Digestive Function and Selective Eating in Children and Adults with Autism.
A related analysis involving 36 autistic participants across child, adolescent and adult age groups also reported reductions in visual, auditory, tactile and digestive hypersensitivity. Language ability did not appear to determine who responded more strongly.
Read: Autism, Hypersensitivity and Language Ability.
Because these publications appear to involve related German research samples, they should not necessarily be counted as two wholly independent replications. They do, however, offer different analyses of potentially meaningful sensory outcomes.
A small exploratory study at Okayama University Hospital administered SSP to six autistic adults between the ages of 21 and 44.
On the study’s main social-communication measure, only the family-rated Social Awareness subscale showed statistically significant improvement. The other measures did not demonstrate clear group-level changes.
This is a useful finding even though it is modest. It suggests that SSP may influence particular aspects of social functioning without necessarily producing broad changes on every standardized measure.
All six participants completed the protocol. Some reported temporary headache, fatigue or sleeplessness, but no participant discontinued because of these effects.
Read: Initial Outcomes of the Safe and Sound Protocol on Patients with Adult Autism Spectrum Disorder.
A 2024 feasibility study examined SSP with 33 speech-therapy clients experiencing voice, throat or breathing complaints.
After SSP, participants reported significant reductions in anxiety, depression and autonomic reactivity. These findings suggest that SSP may have applications beyond auditory sensitivity alone.
A single-child study followed a 20-month-old autistic child who completed two periods of SSP listening as part of a broader intervention plan.
The study reported improvements in language, listening and processing, facial expression, emotional regulation and behaviour. Some changes were maintained at a three-month follow-up.
Read: Social Outcomes in a Child with Autism Spectrum Disorder After Two Rounds of Safe and Sound Protocol.
A published case report described a 10-year-old with functional neurological disorder who received SSP as part of a comprehensive mind-body treatment program.
Improvements were reported in anxiety, depression, stress, body reactivity, mobility, self-regulation and functional symptoms. Because SSP was one component of a broader treatment plan, the study cannot isolate its contribution. It does show how a listening intervention may be integrated into multidisciplinary care when a child has difficulty accessing more active regulation strategies.
A non-randomized study of SSP for adults receiving psychotherapy for trauma or PTSD has been completed, with an actual enrollment of 45 participants.
The study compared psychotherapy plus SSP with psychotherapy alone and measured PTSD symptoms, anxiety, self-reported autonomic symptoms and physiological responses. It was designed as an observational pilot to inform future controlled research.
Its ClinicalTrials.gov record identifies the study as completed. A peer-reviewed results paper was not available at the time this article was reviewed, so the findings should not be assumed in either direction until the results can be evaluated.
The study is nevertheless an encouraging sign that SSP research is moving into trauma-focused clinical populations and incorporating both symptom measures and physiological data.
A 2025 systematic review examined digitally altered sound-based interventions used to address auditory sensitivity, emotional regulation and behavioural functioning.
The review found preliminary evidence for improvement in auditory sensitivity and some emotional and behavioural outcomes. Reported changes included areas such as social behaviour, communication, language and emotional regulation.
The authors also noted that studies differed considerably in their populations, methods and outcome measures. They recommended larger randomized trials and greater consistency in how outcomes are measured.
The review concluded that the existing evidence was promising and that more studies are needed to provide a clearer assessment.
Read the review: Effectiveness of Sound-Based Interventions for Improving Functional Outcomes in Children.
Published SSP or LPP research has included:
There is also significant clinical interest in using SSP with people experiencing anxiety, chronic stress, ADHD, developmental trauma, autonomic symptoms, emotional dysregulation and other forms of sensory overwhelm.
The amount of published evidence differs by population. The existence of research in one group does not automatically establish effectiveness for every other condition. It does, however, offer useful starting points for clinical practice and future investigation.
This is the most consistent positive finding, particularly in autistic children and young people. It is also closely connected to the intervention’s original purpose.
Controlled research has found improvements in processing speech presented with competing words or filtered sound. This may help explain why some clients report that conversation becomes easier to follow or less exhausting.
Studies have reported reductions in auditory, visual and tactile sensitivities. One study also found changes in digestive concerns and selective eating, although these findings need replication.
Improvements have been reported in emotional control, behavioural organization and the ability to recover after activation. These outcomes may be particularly relevant when SSP is used to support participation in another therapy.
Pre–post studies, case research and real-world data have found encouraging changes in anxiety, depression and self-reported autonomic reactivity. More controlled research is needed, but the consistency of these clinical signals makes them worthy of further investigation.
Some studies have reported changes in spontaneous speech, listening, facial expression, social awareness and engagement. These findings do not suggest that SSP changes a person’s neurotype. They suggest that reducing sensory or physiological overwhelm may make existing capacities for communication and connection easier to access.
High-quality clinical research is expensive. Large randomized trials require funding, trained research teams, carefully designed comparison conditions, long-term follow-up and enough participants to produce reliable results.
Pharmaceutical research often has access to established commercial funding pathways because a successful medication can be patented, approved and sold at scale. Practitioner-delivered and non-pharmaceutical interventions - including psychotherapy, sensory approaches and listening therapies - typically do not have access to comparable resources or research infrastructure.
The size of an evidence base reflects more than whether an intervention has value. It is also influenced by:
A smaller evidence base should not be confused with evidence that an intervention does not work. It means that some questions have not yet been studied on the scale required to answer them confidently.
Acknowledging limitations does not invalidate positive results. It helps us understand what conclusions the studies can - and cannot - support.
Smaller studies are often the first step in researching an emerging intervention. They help establish feasibility, identify possible benefits and determine which outcomes should be examined in larger trials.
Their results are meaningful, but less precise than estimates from large, multi-site studies.
When everyone receives SSP, researchers cannot fully separate its effects from therapeutic support, expectation, ordinary music listening, natural change or concurrent treatment.
The early LPP research did include active comparison conditions, which strengthens its findings. More research of this kind with the current SSP would be valuable.
Clients and caregivers provide essential information about changes in daily life. Their observations should not be dismissed simply because they are subjective.
At the same time, people generally know that they have received the intervention. Future studies can strengthen these reports by adding blinded observation, standardized functional measures, auditory testing and appropriate physiological data.
Most studies have examined changes immediately after SSP or within several weeks. Longer follow-up would help determine which effects persist and whether additional listening is useful.
This reflects real clinical practice: SSP is generally intended to support a broader treatment plan rather than replace it.
Combination makes it difficult to isolate the effect of SSP, but it also creates an important research question: Does SSP help clients access or benefit from other forms of therapy more effectively?
Some foundational research involves Porges or researchers closely connected with the theoretical development of SSP. Unyte has also provided equipment or training for certain studies, and Porges has disclosed receiving royalties from the licensed technology.
These connections do not invalidate research. The appropriate scientific response is transparency followed by replication from additional independent research groups.
Current evidence cannot give us a precise answer to questions such as:
These unanswered questions are not evidence against SSP. They are directions for the next stage of research.
Future studies can build on the existing positive findings by examining:
These questions do not arise because existing outcomes are being dismissed. They arise because the findings are promising enough to justify deeper study.
SSP is non-invasive, but “non-invasive” does not necessarily mean that every person will have the same experience.
In the six-person adult autism pilot, temporary headache, fatigue and sleeplessness were reported. Other clinical literature describes the need for breaks, schedule adjustments and careful monitoring when discomfort or activation occurs.
Large studies have not yet established the frequency of these experiences. It is therefore more accurate to describe SSP as generally well tolerated in the small studies published so far while acknowledging that individualized support matters.
Listening should not be treated as an endurance test. Depending on the client, responsible delivery may involve:
People with tinnitus, hearing concerns, migraines, significant sound sensitivity or complex medical or psychiatric presentations may need additional assessment or consultation.
Published research asks what tends to happen across a group under defined conditions. Clinical experience asks what is happening for a particular person in a particular context.
Neither can completely replace the other.
A clinical trial cannot decide whether an individual client’s improvement was meaningful. Conversely, one person’s improvement cannot tell us how frequently another person will experience the same result.
When clients and families describe changes in sound tolerance, sleep, communication, connection, emotional recovery or capacity to participate in therapy, those experiences should not be dismissed because large-scale research has not yet caught up. Clinical observation and lived experience often identify the questions that formal research later investigates.
At the same time, responsible practitioners avoid turning an individual success into a universal promise. We can honour a person’s outcome without claiming that SSP will work identically for everyone.
The balanced position is:
Meaningful clinical outcomes are real and worthy of attention. Research helps us understand how frequently those outcomes occur, what contributes to them and how to offer the intervention more effectively.
A balanced conversation might include the following:
This supports informed choice without either exaggerating the evidence or minimizing the intervention’s potential.
The Safe and Sound Protocol is a promising, research-informed listening intervention with a growing evidence base.
Controlled research on its precursor found improvements in auditory hypersensitivity and aspects of listening, communication and regulation in autistic children and young people. Subsequent studies of SSP have reported encouraging outcomes involving sensory processing, anxiety, mood, autonomic symptoms, social engagement and everyday functioning.
The evidence is not complete, but incomplete evidence is not the same as negative evidence. Existing studies provide legitimate reasons for continued interest, thoughtful clinical use and further investment in research.
Larger and more independent trials could move the conversation beyond the overly simple question of “Does SSP work?” toward more useful questions:
Clinical experience cannot replace research, but neither should it be treated as meaningless. A responsible position holds both: encouraging published findings and meaningful real-world outcomes, alongside curiosity about what future research can teach us.
Unyte’s real-world evidence includes standardized assessments relating to anxiety, depression, trauma symptoms and children’s psychosocial functioning. This information can add valuable practice-based context, although real-world outcome data answer different questions from randomized research.
Unyte also states that its products are not intended to diagnose, treat, cure or prevent disease. SSP should not replace appropriate medical, psychological, developmental or rehabilitative care.
Research reviewed July 2026. This article is provided for education and does not constitute medical advice or a guarantee of individual results.