title: Comparing average levels and peak occurrence of overnight sound in the medical intensive care unit on A-weighted and C-weighted decibel scales.
abstract: Sound levels in the intensive care unit (ICU) are universally elevated and are believed to contribute to sleep and circadian disruption. The purpose of this study is to compare overnight ICU sound levels and peak occurrence on A- vs C-weighted scales.
  
  
  
  This was a prospective observational study of overnight sound levels in 59 medical ICU patient rooms. Sound level was recorded every 10 seconds on A- and C-weighted decibel scales. Equivalent sound level (Leq) and sound peaks were reported for full and partial night periods.
  
  
  
  The overnight A-weighted Leq of 53.6 dBA was well above World Health Organization recommendations; overnight C-weighted Leq was 63.1 dBC (no World Health Organization recommendations). Peak sound occurrence ranged from 1.8 to 23.3 times per hour. Illness severity, mechanical ventilation, and delirium were not associated with Leq or peak occurrence. Equivalent sound level and peak measures for A- and C-weighted decibel scales were significantly different from each other.
  
  
  
  Sound levels in the medical ICU are high throughout the night. Patient factors were not associated with Leq or peak occurrence. Significant discordance between A- and C-weighted values suggests that low-frequency sound is a meaningful factor in the medical ICU environment.
authors.affiliation: Section of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT. Electronic address: melissa.knauert@yale.edu.
authors.forename: Melissa
authors.initials: M
authors.lastname: Knauert
authors.affiliation: Yale School of Nursing, West Haven, CT. Electronic address: sangchoon.jeon@yale.edu.
authors.forename: Sangchoon
authors.initials: S
authors.lastname: Jeon
authors.affiliation: Section of Geriatrics, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT. Electronic address: terrence.murphy@yale.edu.
authors.forename: Terrence E
authors.initials: TE
authors.lastname: Murphy
authors.affiliation: Section of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT. Electronic address: henry.yaggi@yale.edu.
authors.forename: H Klar
authors.initials: HK
authors.lastname: Yaggi
authors.affiliation: Section of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT. Electronic address: margaret.pisani@yale.edu.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Pisani
authors.affiliation: Yale School of Nursing, West Haven, CT. Electronic address: nancy.redeker@yale.edu.
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Redeker
mesh_terms: D003422:Critical Care; D005160:Facility Design and Construction; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009622:Noise; D010362:Patients' Rooms; D011446:Prospective Studies
keywords: A-weighted; C-weighted; Critical care; Low frequency; Noise; Sound