Photobiomodulation Associated with Voice Therapy in Singers with Vocal Symptoms: A Randomized Clinical Trial

干预措施: This study is a randomized controlled clinical trial with two parallel arms and a double-blind design. After providing written informed consent, eligible participants will be randomly allocated into two groups using a computer-generated randomization sequence with allocation concealment through sequentially numbered, opaque, sealed envelopes. Participants and the evaluator responsible for the perceptual-auditory, acoustic, and outcome assessments will remain blinded to group allocation. The therapist responsible for administering the interventions will not participate in the assessments and will be the only individual aware of group assignment. The intervention group will consist of 32 amateur singers who will receive low-level laser therapy combined with vocal training. The control group will consist of 32 amateur singers who will receive sham low-level laser therapy combined with the same vocal training protocol. Before the intervention, all participants will undergo vocal history assessment, eligibility screening, administration of the Voice Symptom Scale, the Singing Voice Handicap Index, and the Vocal Fatigue Index, as well as laryngeal endoscopy to evaluate laryngeal structure and function. Voice recordings will be obtained using a headset microphone connected to a computer, including sustained production of the vowel /?/ at habitual, loud, and soft intensities, connected speech, a standardized sentence, and a one-minute singing sample selected from the participant’s own repertoire. Vocal range profile recordings using ascending and descending glissandos, together with self-assessment of vocal effort and vocal tract discomfort, will also be performed. Participants in the intervention group will receive low-level laser therapy applied to the ventral region of the l