Research
The Science of Sound
What current research says about natural sound, healing and mental health.
Decades of research show that natural sound — birdsong above all — helps people feel calmer and more restored,156 and small clinical trials show it can ease pain and anxiety in hospital17–19 and reduce agitation in memory care.29 Terra brings a real, living soundscape indoors, at a volume you control, so residents and patients can hear the birds outside their window even when they cannot go out.
Numbers in brackets point to the index of papers at the bottom of this page.
What the research shows
Most of us feel calmer in a place full of birdsong. Forty years of research asks whether that feeling shows up in measurable health. The answer is increasingly yes.
Mood and stress
The broadest evidence is a 2021 synthesis in PNAS that pooled 18 experiments on natural sound. People who heard natural sounds reported less stress and annoyance and better mood and health outcomes than comparison groups. Bird sounds did the most for stress and water sounds the most for mood.1 Individual experiments fill in the picture. Six minutes of birdsong lowered anxiety and paranoid thinking in 295 adults, while six minutes of traffic noise worsened depressive mood.5 People recovering from a stressful task settled faster, by skin conductance and heart-rate variability, when they heard birds and water instead of traffic,2021 and a nature-sound break in an office lowered muscle tension and pulse within seven minutes.24
Out in the real world
Real-world studies agree. In a smartphone study of 1,292 people, moments when someone could see or hear birds came with higher wellbeing scores, a lift still visible at the next check-in and present in people diagnosed with depression.6 When researchers hid speakers playing extra birdsong on two Colorado trails, 665 hikers reported feeling more restored.7 Across 26 European countries, people living among more bird species report higher life satisfaction.15
In the hospital
In hospitals, nature sound has a track record. Patients who heard nature sounds during a bronchoscopy were far more likely to rate their pain control as good.17 Ventilated intensive-care patients given 90 minutes of nature sounds had lower blood pressure, less anxiety and agitation, and less pain than controls.1819 The classic 1984 study found surgical patients whose window faced trees rather than a brick wall went home almost a day sooner and needed fewer strong painkillers.16
In memory care
For older adults living with dementia, nature-based approaches — gardens, nature sounds, images and scents — reduce agitation in pooled analyses, and indoor delivery works as well as outdoor.29 A 2024 pilot trial of a designed in-room soundscape reduced residents’ resistance to care.30
Index of papers
The research, paper by paper
Forty-two peer-reviewed papers, reviews and foundational works behind the summary above, grouped by topic. The one-line findings are our plain-language readings; the numbers come from the papers themselves, or where noted, from press coverage of them. Each entry links to the original.
Birdsong, natural sound and mental health
Pooled analyses, lab experiments and real-world studies of how natural sound affects stress, mood and wellbeing.
- 1
Buxton RT et al. (2021) PNAS 118(14): e2013097118
Meta-analysis of 18 studies; 221 park sites
Natural sound lowered stress and annoyance (g = −0.60) and improved health and mood outcomes (g = 1.63). Bird sounds did the most for stress, water sounds the most for mood.
Read the paper → - 2
Ratcliffe E, Gatersleben B, Sowden PT (2013) Journal of Environmental Psychology 36: 221–228
Interviews, 20 people
Bird sounds were the natural sounds most often linked to recovery from stress and attention fatigue. Not all bird sounds help.
Read the paper → - 3
Ratcliffe E et al. (2020) Environment and Behavior 52(4): 371–400
Online ratings, 174 people × 50 bird sounds
Loudness, harmonics, pitch, complexity, familiarity and pattern predict how restorative a bird sound feels.
Read the paper → - 4
Ratcliffe E (2021) Frontiers in Psychology 12: 570563
Narrative review
Natural sounds improve mood and cognition after stress, though findings are not fully consistent across studies.
Read the paper → - 5
Stobbe E et al. (2022) Scientific Reports 12: 16414
Online randomized trial, 295 adults, six minutes
Birdsong reduced anxiety (d ≈ −0.7) and paranoid thinking. Traffic noise increased depressive mood. No effect on cognition.
Read the paper → - 6
Hammoud R et al. (2022) Scientific Reports 12: 17589
Smartphone experience sampling, 1,292 people, 26,856 check-ins
Seeing or hearing birds went with higher mental wellbeing (adjusted difference 1.22). The lift was still there at the next check-in and held for people with depression.
Read the paper → - 7
Ferraro DM et al. (2020) Proceedings of the Royal Society B 287: 20201811
Field playback on two trails, 665 hikers
Hidden speakers adding birdsong raised hikers’ reported restoration, directly on one trail and through perceived bird diversity on the other.
Read the paper → - 8
Sudimac S, Sale V, Kühn S (2022) Molecular Psychiatry 27: 4446–4452
fMRI, 63 people, one-hour walk
Amygdala activity fell after a forest walk but not after an urban walk.
Read the paper → - 9
Bratman GN et al. (2015) PNAS 112(28): 8567–8572
Randomized, 90-minute walk
A nature walk reduced rumination and activity in the subgenual prefrontal cortex.
Read the paper → - 10
Van Hedger SC et al. (2019) Psychonomic Bulletin & Review 26: 522–530
Lab, nature versus urban sound
Cognitive performance improved after natural sound. Mood did not differ.
Read the paper → - 11
Gould van Praag CD et al. (2017) Scientific Reports 7: 45273
fMRI, 17 people
Natural sound shifted default-mode network connectivity outward, raised peak heart-rate variability and sped reaction times.
Read the paper → - 12
Benfield JA et al. (2014) Ecopsychology 6(3): 183–188
Lab mood induction
Mood recovered with natural sound and worsened with traffic noise (as described in press coverage of the study).
Read the paper → - 13
Gilmour LRV et al. (2024) PLOS ONE 19(11): e0311487
Online repeated measures, 68 people
A dawn chorus gave the lowest stress and anxiety. Mixing in traffic noise removed the benefit.
Read the paper → - 14
Cox DTC et al. (2017) BioScience 67(2): 147–155
Cross-sectional survey, about 270 residents
More afternoon birds and more vegetation in a neighborhood went with lower depression, anxiety and stress.
Read the paper → - 15
Methorst J et al. (2021) Ecological Economics 181: 106917
Survey, more than 26,000 people in 26 countries
Bird species richness tracks life satisfaction. In the press summary, 14 extra species was worth about €124 a month in income.
Read the paper →
Physical health, pain and recovery
Hospital and lab studies of nature sound and nature views: pain, blood pressure, heart-rate variability, cortisol and sleep.
- 16
Ulrich RS (1984) Science 224: 420–421
Matched hospital records, 23 versus 23 patients
Surgical patients with a window view of trees stayed 7.96 days versus 8.70, took fewer strong painkillers and drew fewer negative nurse notes.
Read the paper → - 17
Diette GB et al. (2003) Chest 123(3): 941–948
Randomized trial, 80 bronchoscopy patients
A nature mural plus nature sounds gave 4.8 times the odds of good pain control. Anxiety did not differ significantly.
Read the paper → - 18
Saadatmand V et al. (2013) International Journal of Nursing Studies 50(7): 895–904
Randomized trial, 60 ventilated ICU patients, 90 minutes
Lower systolic and diastolic blood pressure, anxiety and agitation, with a larger effect the longer the listening.
Read the paper → - 19
Saadatmand V et al. (2015) Pain Management Nursing 16(4): 483–492
Randomized trial, 60 ventilated ICU patients, 90 minutes
Pain was lower at every measurement, with the effect lasting to 120 minutes.
Read the paper → - 20
Alvarsson JJ et al. (2010) International Journal of Environmental Research and Public Health 7(3): 1036–1046
Lab, 40 people, matched sound levels
Skin conductance recovered faster after stress with natural sound. Heart-rate variability did not differ.
Read the paper → - 21
Annerstedt M et al. (2013) Physiology & Behavior 118: 240–250
Virtual-reality pilot, 30 men
High-frequency heart-rate variability rose only when nature sounds were added to a virtual forest. Cortisol was unaffected.
Read the paper → - 22
Hedblom M et al. (2019) Scientific Reports 9: 10113
Multisensory virtual reality, 154 people
Park and forest settings with birdsong reduced skin conductance. An urban setting did not. The senses could not be separated.
Read the paper → - 23
Jo H et al. (2019) International Journal of Environmental Research and Public Health 16(15): 2649
Lab, 29 women, 60 seconds
Forest sound lowered prefrontal oxygenated hemoglobin, heart rate and sympathetic tone, and improved mood.
Read the paper → - 24
Largo-Wight E et al. (2016) HERD 10(1): 45–51
Randomized trial, 40 office workers, 15 minutes
A nature-sound break cut muscle tension (within seven minutes), pulse and self-reported stress. Silence and music did not.
Read the paper → - 25
Nasari M et al. (2018) Nursing and Midwifery Studies 7: 18–23
Randomized trial, 93 coronary-care patients
Nature sounds and silence both improved sleep quality over usual care, with no difference between them.
Read the paper → - 26
Fatehimoghadam S et al. (2023) Iranian Journal of Nursing and Midwifery Research 28(4): 436–442
Double-blind randomized trial, 80 heart-attack patients
Lower systolic blood pressure and stress than silent headphones.
Read the paper → - 27
Papathanassoglou E et al. (2025) Australian Critical Care 38(3): 101148
Systematic review, 59 ICU randomized trials
Sound interventions reduced pain, improved sleep and lowered cortisol. Music has the stronger evidence base.
Read the paper → - 28
Saskovets M et al. (2025) JMIR Mental Health 12: e69120
Scoping review, 34 studies
Nature sounds are promising but under-studied. Personalization matters.
Read the paper →
Older adults and dementia care
Nature-based care in nursing homes and memory care: agitation, resistance to care and the sound environment itself.
- 29
Choe EY, Lee JY, Montayre J (2025) Healthcare 13(14): 1727
Meta-analysis, 29 studies, 733 people with dementia
Nature-based interventions reduced agitation (g = −0.86). Indoor delivery worked at least as well as outdoor. Four of the studies used nature sounds.
Read the paper → - 30
Talebzadeh A et al. (2024) Innovation in Aging 8(9): igae069
Pilot randomized trial, dementia unit
A designed in-room soundscape reduced resistance to care (−0.81, p = .042). Total agitation scores did not change significantly.
Read the paper → - 31
Devos P et al. (2019) International Journal of Environmental Research and Public Health 16(24): 4904
Design framework
The rationale for supportive soundscapes in dementia care.
Read the paper → - 32
Janus SIM et al. (2021) International Psychogeriatrics 33(6): 627–644
Systematic review, 35 studies
Nursing homes run at 55–68 dB(A). Noise goes with worse sleep and more agitation; music goes with less agitation.
Read the paper → - 33
Whear R et al. (2014) JAMDA 15(10): 697–705
Systematic review, 17 studies
Garden use goes with less agitation. Study quality is poor.
Read the paper → - 34
Yeo NL et al. (2020) The Gerontologist 60(3): e184–e199
Systematic review, 26 studies, 930 residents
Evidence for indoor nature is inconsistent. Horticulture has the best support.
Read the paper → - 35
Tong GYL et al. (2025) Age and Ageing 54(4): afaf084
Systematic review, 84 studies, people 65 and over
Indoor nature interventions are comparable to outdoor ones.
Read the paper → - 36
Moyle W et al. (2018) The Gerontologist 58(3): 478–487
Mixed-methods pilot, 10 residents
A virtual forest brought more pleasure and alertness, but also more fear and anxiety for some residents.
Read the paper →
Children and learning
Classroom studies of natural sound and attention.
- 37
Shu S, Ma H (2019) International Journal of Environmental Research and Public Health 16(2): 293
Virtual classroom, 46 children
Birdsong and water sped attention recovery. Water was best for memory.
Read the paper → - 38
Shu S (2023) Frontiers in Psychology 14: 1131170
335 + 61 children
Birdsong was rated the most restorative classroom sound. It needs to sit at least 5 dB above the background to work.
Read the paper →
Real versus recorded, and the theory behind it
Why natural sound might work, and whether the real thing adds something a recording does not.
- 39
Browning MHEM et al. (2020) Frontiers in Psychology 10: 2667
Six minutes of real versus 360° virtual nature
Both were restorative. Mood rose only outdoors.
Read the paper → - 40
Kaplan S (1995) Journal of Environmental Psychology 15(3): 169–182
Theory
Attention Restoration Theory: natural settings let directed attention rest and recover.
Read the paper → - 41
Ulrich RS et al. (1991) Journal of Environmental Psychology 11(3): 201–230
Theory and experiment
Stress Reduction Theory: natural scenes and sounds trigger a fast, automatic calming response.
Read the paper → - 42
Wilson EO (1984) Biophilia, Harvard University Press
Book
The biophilia hypothesis: people have an innate pull toward other living things.
Read the paper →
Compiled October 2026 from published abstracts and full texts. Terra is not a medical device, and the Terra Station itself has not been studied for health effects. If you work in care or research and would like to study natural sound with Terra, write to health@terralistens.com.
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