MIL-HDBK-1191
SECTION 23 ACOUSTICS
23.1
GENERAL ISSUES
23.1.1
Introduction. This Section deals with guidelines, criteria, and
general approaches to sound problems in military health care facilities. This
information is designed to help a design professional or facility program
manager understand some of the causes of sound/noise problems, and the tools
that are available to address them. The section covers General Issues
(definitions and metrics, sources and receivers), Sound Isolation (separation
of sound and speech privacy between spaces), Room Acoustics (control of noise
within spaces), Mechanical System Noise and Vibration Control, and
Implementation Guidelines (integration and execution of acoustics through
planning, design, construction, and post-construction phases of a project).
Additional requirements and design guidance relating to acoustical design is
contained at Section 8 (HVAC) and Appendix A of this document.
23.1.2
Analysis
23.1.2.1.
Problems covered. This section is directed to acoustics problems
in health care facilities such as speech privacy between offices, sound
isolation between patient rooms, proper level and character of ambient
(background) sound in rooms, control of noise and vibration from mechanical
equipment in buildings, good hearing conditions in public spaces, and general
noise control in work environments.
23.1.2.2.
Problems not covered. This section does not address advanced
acoustics problems such as performance spaces (e.g., lecture rooms, cinemas or
theater), specialized laboratory or meeting spaces (e.g., wind tunnels, animal
research facilities, video teleconference rooms), or highly vibration-
sensitive equipment (e.g., electron microscopes, laser surgery).
23.2
SOUND ISOLATION.
23.2.1
Introduction. Sound isolation is important in military health
care facilities in order to provide privacy for sensitive conversations,
comfort for patients, and isolation of annoying and loud sound levels from
equipment. The STC rating of various constructions (grouped components making
up partitions, doors, windows, floors, etc) which define a space, and Flanking
Sound Transmission are two important variables having the most impact on sound
isolation, and which must be consciously controlled by the medical facility
designer.
23.2.1.1
Sound Transmission Class (STC). STC is the standard single-number
measure of the ability of a material or construction system to block sound.
STC values are used in this section to determine suitable design. STC is
derived from Transmission Loss data measured in a controlled laboratory
environment. A higher STC number indicates better sound isolation. STC
values can range from STC 0 (block no sound) to STC 70 or higher (almost no
sound gets through), but in practical terms, general constructions in most
buildings range from STC 30 to STC 55 or so. Because STC ratings are
determined from laboratory tests, they eliminate variations that would be
related to field installation factors such as size of room, room absorption,
edge conditions, sound leaks, quality of workmanship, and such. Minimum STC
ratings for the envelope components of each room are listed in Appendix "A".
These minimum ratings are intended to assist the medical designer, who will
utilize them along with professional judgement, in providing the amount of
privacy required.
23-1
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