Do neonates hear what we measure? Assessing neonatal ward soundscapes at the neonates ears

TL;DR

This study evaluates how different measurement methods and placements affect the assessment of soundscapes in neonatal wards, emphasizing the importance of ear-level measurements and additional acoustic metrics for accurate neonatal auditory environment characterization.

Contribution

It introduces a comprehensive analysis of microphone placement, bed position, and ward layout effects on neonatal soundscape measurements, advocating for binaural and psychoacoustic metrics in NICU assessments.

Findings

Microphone placement significantly affects noise level measurements.

Bed position influences the noise exposure experienced by neonates.

Binaural and psychoacoustic metrics provide a more accurate characterization of neonatal sound environments.

Abstract

Acoustic guidelines for neonatal intensive care units (NICUs) aim to protect vulnerable neonates from noise-induced physiological harm. However, the lack of recognised international standards for measuring neonatal soundscapes has led to inconsistencies in instrumentation and microphone placement in existing literature, raising concerns about the relevance and effectiveness of these guidelines. This study addresses these gaps through long-term acoustic measurements in an operational NICU and a high-dependency ward. We investigate the influence of microphone positioning, bed placement, and ward layout on the assessment of NICU soundscapes. Beyond traditional A-weighted decibel metrics, this study evaluates C-weighted metrics for low-frequency noise, the occurrence of tonal sounds (e.g., alarms), and transient loud events known to disrupt neonates' sleep. Using linear mixed-effects models with aligned ranks transformation ANOVA (LME-ART-ANOVA), our results reveal significant differences in measured noise levels based on microphone placement, highlighting the importance of capturing sound as perceived directly at the neonate's ears. Additionally, bed position and ward layout significantly impact noise exposure, with a NICU bed position consistently exhibiting the highest sound levels across all (psycho)acoustic metrics. These findings support the adoption of binaural measurements along with the integration of additional (psycho)acoustic metrics, such as tonality and transient event occurrence rates, to reliably characterise the neonatal auditory experience.