Acoustics

Sounds can give a person useful information about a space. People impacted by blindness may snap their fingers, tap a long cane or make another noise to listen for a reflected sound, a process known as “echolocation” (for more information on echolocation, read “How Blind People Use Batlike Sonar ” on the news.sciencemag.org website.

Echolocation may help to detect the size of a room, presence of corridors or proximity of structural barriers (e.g., walls and poles). Within a built space, specific sounds can provide information about the location of specific features, such as elevators. However, the space must be designed to allow all of these sounds to be heard.

Inappropriately high levels of reflected and ambient sound (sound glare) within an environment will result in sound masking. Sound glare interferes with the process of locating an auditory cue and can confuse and tire a listener. Crowds of people, construction or maintenance noise, a jet plane flying overhead or background music in lobbies and elevators can drown out useful auditory information. Layouts that feature large rooms with high, open ceilings, as seen in recent restaurant design trends, result in excessive noise, making navigation or orientation extremely difficult for someone with vision loss. If possible, avoid this kind of layout to ensure all guests and patrons have the best possible experience. Otherwise, consider using noise-masking devices such as white noise generators.

A solid object located between a sound source and a listener can create a sound shadow. Sound shadows can provide useful information, but they can also cause disorientation for a person who relies on specific sound cues for mobility. For example, a temporary display, scaffolds used for building maintenance and repairs or decorative items that are positioned after building construction can distort or block critical sounds.

While a building designer can’t control every occurrence of sound glare or shadowing, several steps should be considered when planning the acoustic design of a space:

• Well-defined, acoustically alive spaces are easier for people impacted by blindness to traverse safely. Position elements such as water fountains, elevators or escalators to create useful sounds. For example, a water fountain could be positioned to indicate a garden or reception hall. An escalator would be a good indicator of a central location that’s an important part of the building’s design.
• Carpets, acoustic ceiling tiles and upholstered furniture absorb sound and dampen reflected sound. Create a good balance of sound absorption and sound reflective materials so that people can “hear” the space (i.e., get information about the space through sound).
• Sound sources may mask other sounds intended to provide important directional cues. Consider the noise produced by elements such as ventilation ducts or air conditioning units. These sounds can be useful in wayfinding, but they should not obscure other important audio cues, such as the sounds from an elevator’s arrival or a public address system.
• Sound masking devices (e.g., white noise devices) can be used effectively in many situations to block unwanted noise, but make sure they don’t dampen all sounds in a space.
• Glass can be an effective sound buffer. Use double-glazed glass that has an established sound-reduction capacity.

Reflected sounds that enable a person to use echolocation are frequently a good source of auditory cues. Consider how the structure and texture of planned circulation routes might interact with user-created sounds (e.g., the tapping of a cane) before building or retrofitting a space.