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World J Crit Care Med. Jun 9, 2026; 15(2): 114240
Published online Jun 9, 2026. doi: 10.5492/wjccm.v15.i2.114240
Noise quantification in the intensive care unit of a tertiary care hospital
Ruchi Gupta, Arshdeep S Chadha, Himanshi Lakra, Rimsha Rehan, Sumit Ray, Department of Critical Care Medicine, Holy Family Hospital, New Delhi 110025, India
Raminder Kalra, Holy Family College of Nursing, New Delhi 110025, India
ORCID number: Ruchi Gupta (0000-0003-2419-165X); Arshdeep S Chadha (0009-0007-5795-6600); Himanshi Lakra (0009-0000-0187-7937); Rimsha Rehan (0009-0000-4264-2042); Raminder Kalra (0009-0005-8079-6030); Sumit Ray (0009-0001-4461-136X).
Co-corresponding authors: Ruchi Gupta and Sumit Ray
Author contributions: Gupta R, Ray S and Chadha AS contributed to conceptualization and design; Gupta R, Kalra R, Lakra H and Rehan R contributed to material preparation, data acquisition, and analysis; Gupta R and Ray S contributed equally to the study and manuscript and are co-corresponding authors. All authors contributed to writing and revising the manuscript.
Institutional review board statement: This study was reviewed and approved by the Ethics Committee of Holy Family Hospital, No. EC/NEW/INST/2021/2040.
Informed consent statement: The study did not involve the collection, use, or recording of any patient data, including identifiable or de-identified health information. No interaction or intervention with patients occurred, and no protected health information was accessed or retained.
Conflict-of-interest statement: The authors report no relevant conflicts of interest for this article.
STROBE statement: The authors have read the STROBE Statement-checklist of items, and the manuscript was prepared and revised according to the STROBE Statement-checklist of items.
Data sharing statement: There is no additional data available.
Corresponding author: Ruchi Gupta, MD, Consultant, Principal Investigator, Department of Critical Care Medicine, Holy Family Hospital, Okhla Road, New Delhi 110025, India. ruchigupta@holyfamilyhospitaldelhi.org
Received: September 16, 2025
Revised: November 28, 2025
Accepted: February 9, 2026
Published online: June 9, 2026
Processing time: 248 Days and 1.6 Hours

Abstract
BACKGROUND

Noise in intensive care units (ICUs) frequently exceeds recommended levels [the World Health Organization (WHO) recommends equivalent continuous noise level (Leq) < 35 dB], arising from alarms, equipment, and staff activity. Elevated sound can disrupt patients' sleep, increase stress, and impair recovery.

AIM

To identify the extent of noise exposure in the ICU.

METHODS

This observational study was conducted in the adult ICU of a tertiary care hospital. Noise was measured using the SERRAX SLM1090 sound level meter, which was placed in the center of the 10-bed ICU at a height of 6 feet above ground level. A 30-minute time window was set to obtain half-hourly Leq, L10, L50, L90 (representing sound levels exceeding 10%, 50%, and 90% of the time, respectively), and maximum sound level (Lmax).

RESULTS

Data were collected over 4 months (December 2024 to March 2025), yielding 5443 half-hourly recordings. The average Leq, Lmax, L10, L50, L90 and sound exposure level were 64.8 ± 2.8 dB, 82.5 ± 4.4 dB, 67.5 ± 2.9 dB, 61.4 ± 3.2 dB, 56.4 ± 2.8 dB and 97.7 ± 2.8 dB, respectively. Nurses’ handover, visitation and twilight hours were the noisiest. Nighttime (1:00 hours to 3:00 hours) was the quietest in the ICU. Lmax in the ICU exceeded the WHO cut-offs for industrial sounds and public addresses of 75 dB and 85 dB in 96.7% and 25.5% of readings, respectively. Twenty-four-hour cumulative sound exposure to the patient for night and evening-night penalties were 68 dB and 70 dB, respectively.

CONCLUSION

The noise exposure in the ICU persistently exceeded WHO-recommended thresholds. Maximum noise occurred during handovers, visitation and twilight activities, indicating that these times would be the most effective for intervention.

Key Words: Intensive care unit noise; Peak noise levels; Average noise equivalent continuous noise level; Peak noise maximum sound level; Day-night noise variation in intensive care unit

Core Tip: The purpose of the study was to quantify the noise pollution in intensive care units (ICUs). The average sound levels were consistently above the World Health Organization recommendations. Peak noise exceeded industrial noise cut-offs. Time periods with maximum noise in the ICU were identified during nursing handovers, visitations and twilight hours. The findings highlight the need to introduce measures for noise control in the ICU.



INTRODUCTION

Intensive care units (ICUs) are highly specialized clinical environments that provide continuous monitoring and advanced therapeutic support for critically ill patients. ICU soundscapes are dominated by frequent equipment alarms, staff interactions, mechanical ventilation systems, and routine clinical activities, resulting in noise levels that consistently surpass international guideline recommendations. While noise above 85 dB can lead to hearing damage, even lower levels may produce adverse effects such as physiological disturbances, reduced speech comprehension, diminished privacy, and heightened psychological stress[1].

In the ICU, noise is a persistent issue that negatively impacts both patients and staff. For patients, disturbed sleep is common and may lead to delirium, prolonged hospital stay, and long-term cognitive impairment[1-3]. For healthcare workers, noise can reduce concentration, impair cognitive performance, and increase the risk of medical errors, thereby posing a serious threat to patient safety by diverting staff from critical responsibilities[4]. In recognition of these risks, the World Health Organization (WHO) advises that ICU noise should not exceed 35 dB during the day and 30 dB at night[5].

Research consistently shows that ICU noise levels range from 60 dB to 85 dB, well above recommended limits[6-8]. Alarms, life-support systems, and staff interactions frequently elevate noise levels above 85 dB, creating both physiological and psychological strain in critically ill patients. Elevated noise induces stress responses, such as increased heart rate and blood pressure, and continuous exposure amplifies anxiety[4,6]. The following study was planned and conducted in a tertiary care ICU to understand the extent and day-night variation in sound levels.

MATERIALS AND METHODS

This observational study was conducted in the adult ICU of a tertiary care hospital over 4 months (December 2024 to March 2025). Noise was measured using the SERRAX SLM1090 sound level meter, which was placed in between the 10-bed ICU at a height of 6 feet above ground level. The sampling window was set to 30 minutes to obtain half-hourly recordings of equivalent continuous noise level (Leq), L10, L50, L90 (representing sound levels exceeding 10%, 50%, and 90% of the time, respectively), maximum sound level (Lmax), and sound exposure level (SEL). SEL is the total energy of a sound event normalized to 1 second.

The 24-hour cumulative sound exposure experienced by the patient and ICU staff was calculated using the day-night average sound level (Ldn) and the day-evening-night sound level (Lden). The Ldn is the average equivalent sound level over 24 hours, with a 10 dB penalty for noise during nighttime hours (22:00 hours to 07:00 hours). The Lden or community noise equivalent level is the average sound level over 24 hours. It was calculated with a 5 dB penalty during the evening hours (19:00 to 22:00) and a 10 dB penalty during the nighttime hours (22:00 hours to 07:00 hours).

Statistical analysis

The statistical analysis was conducted using the R programming language, leveraging several specialized packages for data manipulation, visualization, and statistical reporting.

Data processing and management: Initial data handling involved importing raw measurements from spreadsheet formats. Time-series variables were meticulously parsed and converted into appropriate datetime objects to facilitate temporal analysis. New features, such as distinct date indicators and standardised time intervals (e.g., 30-minute slots), were derived to enable detailed temporal aggregation. Data was then aggregated to compute daily and half-hourly descriptive statistics. For various environmental metrics (e.g., Lmax, L90, L10, L50, Leq, SEL), daily means and standard deviations were calculated. Furthermore, specific thresholds were applied to identify and quantify events exceeding predetermined levels, yielding counts and percentages of high-level occurrences for Lmax values (e.g., 75, 85, 90, 95, 100, 105, 110 dB).

Descriptive statistics and data visualization: Descriptive statistics for aggregated metrics were summarized and presented in structured tables. These tables primarily included daily and half-hourly averages (means) of the noise metrics. The ggplot2 package was utilized for comprehensive visual representation. Daily mean values of key environmental indicators (Lmax, Leq, SEL, L90, L10, L50) were illustrated using line and point plots, allowing observation of trends over time. Additionally, a series of heatmaps was generated to visualize the 24-hour cyclical variations of different metrics (Lmax, L90, L10, L50, Leq, SEL) in 30-minute intervals, with the mean values of these metrics used for color mapping to represent intensity.

Guidelines compliance assessment: To evaluate adherence to established guidelines, a compliance analysis was performed. This involved comparing aggregated environmental metrics against relevant reference limits. The analysis quantified total measurements, identified exceedance for specific metrics, and calculated the corresponding percentage of exceedances, as well as average and maximum exceedance values when mean Leq and mean Lmax exceeded the WHO limits.

RESULTS

Data were collected from December 1, 2024 to March 1, 2025 in the adult ICU regarding noise levels using a sound level meter. Forty-eight recordings were made per day in 30-minute time windows to obtain Leq, L10, L50, L90, Lmax, and SEL. A total of 5443 (2721 hours of recordings) half-hourly measurements were recorded. This excluded 180 hours of data due to machine downtime (e.g., calibration, repairs, recharging, etc.). These were averaged to catalog 24-hour diurnal variations in the sound metrics (112-115 recordings in every 30-minute time window over 4 months). All focus parameters remained above WHO-recommended noise levels with an average Leq of 64.8 ± 2.8 dB and average Lmax of 82.5 ± 4.4 dB. The L10, L50, L90 and SEL were 67.5 ± 2.9 dB, 61.4 ± 3.2 dB, 56.4 ± 2.8 dB and 97.7 ± 2.8 dB, respectively (Table 1).

Table 1 Average monthly and overall maximum sound level, L10, L50, L90 (representing sound levels exceeding 10%, 50%, and 90% of the time, respectively), equivalent continuous noise level and sound exposure level.

Lmax
L90
L10
L50
Leq
SEL
December 202482.3 ± 4.956.5 ± 3.167.6 ± 3.261.5 ± 3.464.8 ± 2.997.4 ± 2.9
January 202582.1 ± 4.555.5 ± 2.667.0 ± 2.860.6 ± 3.064.2 ± 2.696.7 ± 2.6
February 202582.8 ± 4.056.4 ± 2.967.9 ± 2.861.5 ± 3.265.1 ± 2.797.7 ± 2.7
March 202582.7 ± 4.257.1 ± 2.367.6 ± 2.861.6 ± 2.964.9 ± 2.797.5 ± 2.7
December 2024 - March 202582.5 ± 4.456.4 ± 2.867.5 ± 2.961.3 ± 3.264.8 ± 2.897.7 ± 2.8

In the 5443 half-hourly time windows, Lmax exceeded 75 dB, 85 dB and 100 dB in 96.7%, 25.5% and 0.3% of recordings, respectively (Figure 1). An average of 16 out of 48 readings exceeded 85 dB daily (Supplementary Table 1). In the 121-day recordings, Lmax was above 85 dB in all days, 90 dB in 108 days (89%), 95 dB in 39 days (32%) and 100 dB in 13 days (1%) (Supplementary Table 2). We calculated the diurnal variance in noise and Leq varied 10% around the mean. All other sound metrics showed similar variations (Figure 2). Maximum noise occurred between 8:00-9:00 hours, 12:30-13:00 hours, 13:30-14:30 hours, 17:00-17:30 hours, and 20:00-21:00 hours, corresponding to nurses’ handover and visitation times. Minimum noise levels were noted between 01:00 and 03:00 hours (Figure 3).

Figure 1
Figure 1 Maximum sound level scatter plot over 4 months (5443 time windows). WHO: World Health Organization; Lmax: The highest sound level recorded during the measurement period (30 minutes); Dec: December; Jan: January; Feb: February; Mar: March.
Figure 2
Figure 2 Diurnal variation in L10, L50, L90 (representing sound levels exceeding 10%, 50%, and 90% of the time, respectively), equivalent continuous noise level, maximum sound level and sound exposure level (Baseline values were defined as the overall mean during stable periods; percentage change reflects deviation relative to baseline). A: L10 - noise levels exceeded for 10% of the time; B: L50 - noise levels exceeded for 50% of the time; C: L90 - noise levels exceeded for 90% of the time; D: Equivalent continuous noise level. The average sound energy over a given time period; E: The highest sound level recorded during the measurement period; F: Sound exposure level is the total energy of a sound event, normalized to 1 second. L10, L50, L90: Representing sound levels exceeding 10%, 50%, and 90% of the time, respectively; LEQ: Equivalent continuous noise level; Lmax: Maximum sound level; SEL: Sound exposure level.
Figure 3
Figure 3 Heat maps illustrating the 24-hour acoustic cycle of different noise parameters measured in half-hour intervals over the study period. The color intensity indicates the relative magnitude of the acoustic parameter during the respective time intervals. Scale bar: 30 minutes. A: L10 - noise levels exceeded for 10% of the time; B: L50 - noise levels exceeded for 50% of the time; C: L90 - noise levels exceeded for 90% of the time; D: Equivalent continuous sound level. The average sound energy over a given time period; E: The highest sound level recorded during the measurement period; F: Sound exposure level is the total energy of a sound event, normalized to 1 second. L10, L50, L90: Representing sound levels exceeding 10%, 50%, and 90% of the time, respectively; LEQ: Equivalent continuous noise level; Lmax: Maximum sound level; SEL: Sound exposure level.
Nursing handover

The nursing handover [morning handover (8:00-9:00 hours), afternoon handover (13:30-14:30 hours) and night handover (20:00-21:00 hours)] had an average Leq, L10, L50, L90, Lmax and SEL 67, 70, 64, 59, 84 and 99 dB, respectively (Table 2). 100% and 32% of Lmax recordings were above 75 dB and 85 dB, respectively (Table 3). A maximum increase of 6.3% in L90 (baseline sound levels) occurred during morning handover (Figure 2C).

Table 2 Sound metrics during activity hours.

Lmax
L90
L10
L50
Leq
SEL
Nurses handover (8:00-9:00 hours)83.9 ± 4.159.4 ± 2.370.0 ± 2.064.7 ± 2.167.3 ± 1.999.8 ± 1.9
Nurses handover (13:30-14:30 hours)83.7 ± 3.858.1 ± 2.169.1 ± 1.863.4 ± 2.366.3 ± 1.998.8 ± 1.9
Nurses handover (20:00-21:00 hours)83.2 ± 3.758.5 ± 2.269.7 ± 1.764.1 ± 2.066.8 ± 1.799.4 ± 1.7
Visiting time (12:30-13:00 hours)83.0 ± 4.458.6 ± 1.869.5 ± 1.964.1 ± 2.166.7 ± 2.099.2 ± 2.0
Visiting time (17:00-17:30 hours)83.0 ± 4.057.6 ± 2.268.6 ± 2.062.9 ± 2.365.8 ± 2.098.4 ± 2.0
Night time avg (22:00-6:00 hours)81.1 ± 4.854.8 ± 2.765.9 ± 3.259.4 ± 3.063.1 ± 3.095.7 ± 3.0
Night time (1:00-2:00 hours)79.6 ± 4.654.0 ± 2.864.5 ± 3.558.2 ± 3.061.8 ± 2.894.3 ± 2.8
Night time (2:00-3:00 hours)79.9 ± 4.754.1 ± 2.764.8 ± 3.558.3 ± 2.962.1 ± 2.894.6 ± 2.8
Twilight (4:00-6:00 hours)83.7 ± 4.355.9 ± 2.567.7 ± 2.560.9 ± 2.665.1 ± 2.497.6 ± 2.4
Table 3 Maximum sound level recordings above 75 dB and 85 dB during nurses’ handover, visiting, night time and twilight, n (%).

Number of recordings
Events exceeding 75 dB
Events exceeding 85 dB
Nurses’ handover (morning, afternoon, night)679679 (100)218 (32)
Visiting (morning and evening)114113 (99)38 (33)
Night time (22:00-6:00 hours)11341006 (89)143 (13)
Twilight (4:00-6:00 hours)450445 (99)155 (34)
Attendant visitation

Patient’s attendant visiting time (12:30-13:00 hours and 17:00-17:30 hours) had an average Leq, L10, L50, L90, Lmax, and SEL of 66, 69, 63, 58, 83, and 99 dB, respectively (Table 2). 99% and 33% of Lmax recordings were above 75 dB and 85 dB, respectively (Table 3).

Nighttime

During nighttime (22:00-6:00 hours), average Leq, L10, L50, L90, Lmax and SEL were 63, 66, 59, 54.8, 81 and 95.2 dB, respectively (Table 2). The quietest time in the ICU was between 01:00-03:00 hours, with all metrics showing a > 4% decrease from the mean (Figure 2). Lmax was above 75 dB and 85 dB in 89% and 13% of samples, respectively (Table 3). There was a steep increase in sound decibels, peaking between 4:00 hours and 6:00 hours (twilight hours), corresponding to the patient’s routine care, positioning, sampling, and other activities. During the twilight hours, the average Leq, L10, L50, L90, Lmax, and SEL were 65.1, 67.7, 61, 56, 84, and 98 dB, respectively (Table 2). Lmax exceeded 75 dB, 85 dB and 95 dB in 99%, 34% and 2% of the readings during this time (Table 3).

24-hour cumulative sound exposure

The Ldn calculated with nighttime compensation was 68.6 dB. The Lden with both evening and nighttime compensation was 70.4 dB.

DISCUSSION

Noise pollution in the ICU has long been recognized as a significant environmental stressor that can negatively impact patient outcomes and staff performance. WHO has consequently recommended keeping average noise levels (Leq) below 35 dB and peak noise (Lmax) below 40 dB in ICUs[5]. In our study, Leq levels persistently exceeded the WHO-recommended noise thresholds. Lmax, the loudest point reached during a noise measurement, was twice the level WHO recommends. Our findings were consistent with previous reports, which reports Leq ranging from 55 dB to 65 dB and Lmax > 80 dB in intensive care settings. These observations have remained unchanged over many decades across multiple ICUs, irrespective of specialty, setting (closed or open), and country[4,6-8].

In our study, the ambient or background noise in the ICU, represented by L90, was significantly above WHO recommendations. This shows that patients and healthcare workers in the ICU are constantly exposed to unacceptable levels of sound energy. High background noise in the ICU may be attributed to constant conversations, equipment, alarms and general patient care. Healthcare staff often become accustomed to or accept noise in the ICU. However, noise has a significant physiological and psychological impact on patients by increasing anxiety, sensory overload, and potentially contributing to long-term emotional trauma[1].

The extent of noise pollution in the ICU can be gauged by the WHO-recommended sound cut-offs for recognized noisy areas, which most people can relate to. For supermarkets and industrial areas, the WHO has recommended limiting the Leq to 60 dB and 70 dB, respectively[9]. As shown in Figure 4, the average Leq in our ICU remained above the supermarket threshold throughout the day. Loud, intermittent noise (L10) approached the industrial noise cut-off of 70 dB during nurses’ handover and visitation.

Figure 4
Figure 4 The 24-hour average of equivalent continuous noise level, L90, L10 and maximum sound level. L10 - noise levels exceeded for 10% of the time; L90 - noise levels exceeded for 90% of the time. L90 is often considered background noise. L10, L90: Representing sound levels exceeding 10% and 90% of the time, respectively; LEQ: Equivalent continuous noise level; Lmax: Maximum sound level; WHO: World Health Organization; ICU: Intensive care unit.

According to the Occupational Safety and Health Administration[10], employee noise exposures of > 85 dB in an 8-hour time-weighted average may be associated with hearing loss. Sound levels above 85 dB are associated with increased incidence of irritation, anxiety, sleep disturbances, and even delirium[11]. During the 4 months of our study, noise exposures > 85 dB exceeded the threshold an average of 16 times per day, or a quarter of all observations. Although recorded as isolated events, few Lmax readings exceeded 110 dB, the WHO cutoff for peak industrial noise (Figure 4).

Nursing handover periods, which are vital to care continuity, were marked by considerably higher noise levels with Leq increasing by more than 5%. The metrics were highest during the morning rounds, with the most significant change observed in the background noise (L90) and peak sounds (Lmax) (Figure 2). During the nurses’ handover, Lmax was above 85 dB in a third of readings. A total of 3% of handover readings recorded Lmax over 100 dB (Supplementary Table 3). This illustrates that the nursing team's vigorous action and dialogue further contributed to added noise burden. Prior studies have also noted that noise peaks were frequently recorded during shift changes and medical rounds, leading to Lmax reaching 85 dB[4,8,12].

Noise reduction was observed during overnight spans, albeit still above acceptable levels, with 90% of nighttime samples recording Lmax values above 75 dB (Table 3). In our study, a significant increase in noise level was observed during the twilight hours (4 am-6 am). Noise exposures of > 85 dB were recorded in 34% readings made between 4 am and 6 am. This time in the ICU was allocated to patient care, positioning, sampling, and other routine nursing care and was therefore associated with intense activity.

Sudden sound spikes can cause transition from deeper sleep stages to lighter ones or to full wakefulness in patients with drastic reductions in both the active phase of sleep and slow-wave sleep correlating with peak dB[13,14]. This leads to sleep fragmentation, altered sleep architecture, reduced total sleep time, and impaired perceived sleep quality in ICU patients[13,15]. Nighttime noise, especially above 80 dB, has also been reported as an independent predictor of delirium[11,14,16]. A temporal pattern is noted between delirium and periods of increased nighttime noise and poor sleep, suggesting a cumulative neurocognitive effect[17,18].

Cumulative sound energy transferred to people exposed to noise is calculated using Lden and Ldn. The 2022 update of the WHO European region on environmental noise[5] strongly recommends maintaining Ldn < 45 dB and Lden < 53 dB in the community for road traffic noise. In our study, Ldn and Lden were 51% and 32% above the recommended limits at the community level, underscoring the extent of sound exposure among patients and ICU staff. In 1994, Meyer et al[6] performed a systematic evaluation of noise in the ICU and described it as “as loud as a busy roadway or a factory floor”. The strength of the present study is its more extended data-collection period, compared to a few weeks in previous studies. Various sound metrics were averaged across all time points, making the data more robust and comprehensive and providing an accurate representation of diurnal variation.

Limitations

The current observational study was performed in a single ICU. The results may not reflect the noise burden across all ICUs due to variability in institutional practices and differences in environmental, structural, and cultural factors. The sound meter was placed at a fixed position in the 10-bed ICU and failed to record sound levels in specific areas, namely the nurses’ station and the patient’s immediate vicinity. The sound levels at the patient’s immediate bedside were not recorded. The monitors and ventilator alarms are most prevalent in the patient's vicinity and therefore have the most significant impact on patients. This needs to be recorded in future studies to better understand the importance of regulating alarm volumes and limits.

CONCLUSION

The average and maximum background noise in the ICU exceed international guidelines. The maximum noise occurred during handovers, visitation and twilight activities, indicating that these times would be the most effective for intervention. The study highlights the importance of including noise as one of the quality indicators to be observed and its integration in the structural design of ICUs.

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Footnotes

Peer review: Externally peer reviewed.

Peer-review model: Single blind

Corresponding Author’s Membership in Professional Societies: Indian Society of Critical Care Medicine, No. 15/g-5 73.

Specialty type: Critical care medicine

Country of origin: India

Peer-review report’s classification

Scientific quality: Grade C, Grade C

Novelty: Grade B, Grade D

Creativity or innovation: Grade B, Grade D

Scientific significance: Grade B, Grade D

P-Reviewer: Bou Sanayeh E, MD, United States; Kothekar AT, MD, Professor, India S-Editor: Bai SR L-Editor: Filipodia P-Editor: Yu HG

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