Another way to make auditory alarms such as bells and sirens accessible to deaf people is through the use of volume amplification; in other words, to make the bell or siren very loud and for some, a loud siren that changes pitch from lower to higher frequencies again and again.
The biggest drawback to using this method is often the volume is far in excess of what is comfortable to others who are in the vicinity. Also, depending of the level of deafness of your student, there may be a proximity point that becomes too far for the alarm to be heard.
Therefore, it is more common and most likely the safest option for public places to use flashing alarms as a flashing alarm is accessible to all in the immediate environment.
If you would like to know more about this technology, you can contact Word of Mouth Technology
This service is based in Melbourne, but provides options for online ordering.