Audible communication is an important source of information for people with vision loss. A properly installed public address system can efficiently provide location and emergency or event-related facts.
The volume of voice signals should exceed background noise by at least 10 dB. Mid-range frequencies (500 – 3,000 Hz) with sound equalization are easiest to hear. Spaces with public address systems should be designed to minimize sound deflection and reflection. Alarm signals should be set at 15 dB above background noise (to a maximum level of 120 dB).
When audio public address systems are used, equivalent information should be given through visual display units to accommodate people who are deaf, deafened, hard of hearing or deafblind. Text message alert systems are rapidly evolving and have great potential to provide real-time information in accessible formats directly to an individual’s smartphone. However, they cannot be relied upon as the only means of providing alerts, since not all individuals will have the technology to receive the alerts.