That's the international symbol for deafness. Some places (like libraries, and help desks)are being equipped with hearing loop systems at counters and enquiry desks, which can greatly enhance communication for people with hearing aids. Anyone with a suitable hearing aid (such as those supplied by the National Health Service) can switch it to the 'T' position and immediately benefit from the improved sound quality which the loop system produces. Not only is the sound clearer and stronger but also background noise is reduced

ok thank you