Dear David,

I love visiting with my grandcat. But sometimes I have to talk loudly so she can hear me.

I asked my friend Christine Portfors why that is. She’s a biologist at Washington State University.

She told me it’s all about the hair cells inside our ears.

They aren’t really hairs. They’re sensory cells. Hair cells have tiny, bristle-like tufts that stick out—called cilia—that look a little bit like hairs.

Those hair cells are why we can hear.

First, sounds funnel into our ears. They bonk into the ear drum and make it vibrate. Then, three itty, bitty bones make those … » More …