Acoustics

Libraries are vibrant community gathering spaces, with an expanding range of uses.
 

A modern library often hosts multiple simultaneous activities requiring both concentration and focused thinking in tandem with large group events that are highly participatory. Thus, the design for acoustic quality needs to set the appropriate balance of activities and building zones that are acoustically connected but separate.

While it is obvious that public gathering areas must allow many forms of audible communication, this can be contrary to activities best supported by an acoustically controlled environment where solitude and reflection are possible.

A careful balance of acoustic comfort and acoustic privacy is the optimal design goal. Good planning can ensure correct placement of acoustically compatible functions.

Technical elements in acoustic design

Libraries are dynamic places where open, multi-functional and accessible areas (like reading areas, exhibition spaces and atria) are connected to each other and to private spaces (such as semi-enclosed offices, workrooms and meeting rooms).

For all these building zones, it is important to consider:

• hearing conditions for adequate communication between occupants
• speech intelligibility for communication purposes
• privacy from external or adjacent activity noise that interferes with concentration and conversely overhearing private conversations
• excessive noise build-up due to occupational noise.

Acoustic design performance

Acoustic design performance can be summarised in three primary areas:

Sound isolation/sound containment
This means controlling the transfer of sound from one space to another. A high degree of sound isolation is provided by high density and airtight constructions and also by factoring the “weakest points” in the partition such as glazing and doors that can degrade an overall separation. Sound containment, and the level of background noise, also affects speech privacy between zones of activity.

Noise management
Constant and neutral noise (background noise) in a space provides a beneficial masking effect to activities that otherwise could be distracting. It is important to acoustically control the level of background noise generated by ventilation or operable facade systems relative to residual occupational noise.

Interior acoustic quality
Enclosed room acoustics is a function of room volume, the shape, and architectural finishes and features. Large areas of hard, reflective surface finishes within enclosed spaces may cause excessively high reverberance, which in turn accentuates background noise and occupational noise in the spaces. This may also result in a poor level of speech intelligibility.

For further information, refer to the Building Code of Australia and Australian Standard 2107: Design Sound Levels and Reverberation Times for Building Interiors. An acoustic engineer is commonly consulted during the building application phase as well as during the building design and construction.

Acoustic treatment in renovated buildings

Library buildings may undergo a number of refurbishments in their lifetime as the way they are used changes. Libraries can also be located in buildings that were originally constructed for a different purpose. There may be a need to retrofit acoustic treatments into existing buildings. Acoustic panels can be hung from ceilings or walls, they can also be built into partitions, temporary walls and false ceilings. Acoustic treatment options are available in a variety of styles to suit different designs and aesthetics, they can range from simple felt panels to acoustic enhanced artworks. Furniture with built in acoustic features, such as high backed chairs and booths, can assist with sound containment.