Infant rooms (including airborne infection isolation rooms),
staff work areas, family areas, and staff lounge and sleeping areas
and the spaces opening onto them shall be designed to produce
minimal background noise and to contain and absorb much of the
transient noise that arises within them.
- In infant rooms and adult sleep areas, the combination of
continuous background sound and operational sound shall not exceed
an hourly Leq of 45 dB and an hourly L10 of
50 dB, both A-weighted slow response. Transient sounds or
Lmax shall not exceed 65 dB, A-weighted, slow response
in these rooms/areas.
- In staff work areas, family areas, and staff lounge areas, the
combination of continuous background sound and operational sound
shall not exceed an hourly Leq of 50 dB and an hourly
L10 of 55 dB, both A-weighted slow response. Transient
sounds or Lmax shall not exceed 70 dB, A-weighted, slow
response in these areas.
To achieve the required noise levels in infant rooms and adult
sleep rooms, building mechanical systems and permanent equipment in
those areas shall conform to Noise Criteria (NC) -25 based on
manufacturers' noise ratings with allowance for other sound sources
and adjustment for room loss if less than 10 dB. Areas in open
communication with infant rooms and adult sleep rooms shall conform
to NC-30. Building mechanical systems and permanent equipment in
other areas specified in the Standard shall conform to a maximum of
NC-35. Building mechanical systems include heating, ventilation, and
air conditioning systems (HVAC) and other mechanical systems (e.g.,
plumbing, electrical, vacuum tube systems, and door mechanisms).
Permanent equipment includes refrigerators, freezers, ice machines,
storage/supply units, and other large non-medical equipment that is
Where personal address speakers are located in sensitive areas,
announcing systems shall have adjustable volume controls for the
speakers in each room and for each microphone that sends signal
through the system.
Speech privacy and freedom from intrusive sounds shall be
provided by acoustic seals for doors and building to meet STC
criteria (below) for demising partitions in infant rooms, on-call
and sleep rooms, family transition rooms, and conference rooms or
offices in which sensitive staff and family information is
discussed. All other penetrations for conduits, inset boxes, pipes,
ducts, and other elements in sound demising partitions shall be
sealed airtight to prevent noise flanking (leakage) through gaps and
Interpretation: The acoustic environment is a
function of both the facility (e.g., building mechanical systems and
permanent equipment, the intrusion of exterior sounds, the sound
containment afforded by doors and walls, and the sound absorption
afforded by surface finishes) and operations (e,g, the activities of
people and function of medical equipment and furnishings).
The acoustic conditions of the NICU should favor speech
intelligibility, normal or relaxed vocal effort, speech privacy for
staff and parents, and physiologic stability, uninterrupted sleep,
and freedom from acoustic distraction for infants and adults. Such
favorable conditions encompass more than the absence of noise and
require specific planning for their achievement. Speech
Intelligibility ratings in infant areas, parent areas, and staff
work areas should be "good" to "excellent" as defined by the
International Organization for Standardization ISO 9921:2003. Speech
intelligibility for non-native but fluent speakers and listeners of
a second language requires a 4 to 5 dBA improvement in
signal-to-noise ratio for similar intelligibility with native
speakers. The Leq, L10 and Lmax
limits will safeguard this intelligibility and also protect infant
The permissible noise criteria of an hourly Leq of 45
dB, A-weighted, slow response in infant rooms and adult sleep areas
is more likely to be met in the fully operational NICU if building
mechanical systems and permanent equipment in those areas and the
areas in open communication with them conform to NC-25 or less.
NC-25 translates to approximately 35 dBA of facility noise. A
realistic addition of 10 dBA of operational noise above this
background will result in an Leq of about 45 dBA. Limiting
operational noise to only 10 dBA above the background will require
Acoustically absorptive surfaces reduce reverberation and,
therefore, sound levels at a distance from the sound source. When
possible, two perpendicular walls should be covered with sound
absorptive surface materials with an NRC of at least 0.65. Where
this is not possible the upper portions of all four walls (above
areas likely to be damaged by the movement of equipment) should be
covered with such material. Glass should be limited to the area
actually required for visualization in order to leave wall surface
available for absorptive surface treatment. While a variety of
flooring will limit impact noise somewhat, specialized carpeting
offers the most protection.
Fire alarms in the infant area should be restricted to flashing
lights without an audible signal. The audible alarm level in other
occupied areas must be adjustable. Telephones audible from the
infant area should have adjustable announcing signals.
The type of water supply and faucets in infant areas should be
selected so as to minimize noise, and should provide instant warm
water in order to minimize time "on".
Noise-generating activities (e.g., linen and supply carts,
conference areas, clerk's areas, multiple-person work stations, and
travel paths not essential to infant care), permanent equipment and
office equipment should be acoustically isolated from the infant
area. Vibration isolation pads are recommended under leveling feet
of permanent equipment and appliances in noise-sensitive areas or
areas in open or frequent communication with them.
Post-construction validation of specifications for the building
mechanical systems and permanent equipment should include noise and
vibration measurement, reporting, and remediation. Measurement of NC
levels should be made at the location of the infant or adult bed or
at the anticipated level of the adult head in other areas. Each bed
space must conform to the Standard.
With space at a premium, many incompatible adjacencies are
possible in NICU designs (e.g., break area, meeting room, or
mechanical room sharing a wall with an infant room or adult sleep
room). Specialized wall and floor/ceiling treatments will help to
meet criteria in these non-optimal conditions.
The criteria below are for sound transmission loss (TL) or
attenuation through horizontal barriers (e.g., walls, doors,
windows) and vertical barriers (e.g., between floors). The Sound
Transmission Class (STC) rating spans speech frequencies and is
relevant for separation of spaces with conversational and other
occupant-generated noise. The Noise Reduction (NR) rating, which
covers a wider frequency span, is more relevant for mechanical noise
dominated by low frequencies. The recommended criteria for TL below
apply to barriers between adjacent spaces and infant areas or adult
rest or sleep rooms13.
|Meeting room with amplified sound
|Staff work area
|Administrative office, conference
Sound transmission from the exterior of the building should meet
the NC criteria inside all spaces identified in the Standard.
It is advisable to enlist the services of an acoustical engineer
from the onset of the project through post-construction validation.
This specialty service is usually not covered by architectural fees
and can assist in program and design development, design of
mechanical systems, specification of equipment and building
construction, and test and balance validation. Enlistment of
acoustical services late in the design process often results in
fewer and more costly options for meeting performance