When, if you're using a whistling kettle, do you pour the tea?

When boiling a pot of tea with a whistling kettle on the hob, do you pour the water just as it starts to whistle, or when the whistle is at its loudest? Or at any other time? This answer will solve an age old argument with my brother, who hates the sound, and insists on leaping up to quell the noise every time I fancy a cup. Ahh, family these days...