Impact of Auditory Environments on Pain in Fibromyalgia: a 4×4 Crossover Trial

Participants receive a standardized 20-minute auditory exposure to curated natural soundscapes via high-fidelity open-back reference headphones powered by a DAC/amplifier and corrected for frequency response using calibration software. Participants are randomly assigned one of 22 recordings. Each includes 10-second fade-in/out effects and are calibrated to 45-55 dB. The stereo recordings (320-kbps MP3, 48 kHz/24-bit) feature biophony (e.g., bird vocalizations) and geophony (e.g., rainfall), free of urban sounds and selected for ecological validity based on predefined criteria: (i) recognizable/context-specific sounds; (ii) culturally neutral; (iii) foreground presence and depth; (iv) no prolonged silence; (v) no technical artifacts. During exposure, they lie supine in a 60° Fowler's position on a therapy table, with sensory input minimized through auditory isolation and controlled ambient conditions. The session involves active, causal listening under continuous researcher supervision.

Participants receive a standardized 20-minute auditory exposure to curated urban soundscapes, using the same equipment and technical specifications as all other intervention conditions. Each participant is randomly assigned one of 22 recordings, calibrated to 45-55 dB (Leq,20min). The recordings feature anthropophony (e.g., unintelligible background speech) and technophony (e.g., transportation-related sounds), free of natural sounds and selected for ecological validity based on the same predefined criteria as the natural soundscapes. To prevent semantic processing, participants are pre-screened and post-session reconfirmed to ensure they do not understand the languages used. During exposure, participants lie supine in a 60° Fowler's position on a therapy table, with sensory input minimized through auditory isolation and controlled ambient conditions. The session involves active listening in a causal mode and is conducted under continuous researcher supervision.

Participants receive a standardized 20-minute auditory exposure to broadband sounds (i.e., white or pink noise), using the same equipment and technical specifications as all other intervention conditions. Each participant is randomly assigned to one of the two noise types, with equal distribution across conditions. The stimuli are generated using professional audio software and calibrated to 50 dB (Leq,20min). During exposure, participants lie supine in a 60° Fowler's position on a therapy table, with sensory input minimized through auditory isolation and controlled ambient conditions. The session involves active listening in a causal mode and is conducted under continuous researcher supervision.

Participants receive a standardized 20-minute exposure to blank audio (silence), using the same equipment and technical specifications as all other intervention conditions. At study onset, participants are informed they will hear a range of environmental sounds, including some that may be inaudible (i.e., present but beyond the range of human hearing). During the placebo condition, a blank recording is played, producing silence, while participants remain unaware of whether they are receiving an active or placebo stimulus. This attention-control condition ensures procedural consistency while delivering no auditory stimulation. During exposure, participants lie supine in a 60° Fowler's position on a therapy table, with sensory input minimized through auditory isolation and controlled ambient conditions. The session involves active listening in a causal mode and is conducted under continuous researcher supervision.