Is it a bird?

SIR – Professor Myung-jin Bae of Soongsil University in Seoul suggests that a quacking car horn is more effective than a honking noise as it is less unpleasant (report, June 26)

I can certainly vouch for the “quacking-sounding” toy horn on my handle bars being pedestrian-friendly. Walkers’ reactions are so funny as they come to a sudden halt and look skywards – only to find me wishing to overtake in a cautious manner. Generally they are grateful, and amused by my unusual warning. Noreen Mcburney Carnoustie, Angus