Listen closely. A cooing or murmuring sound is interspersed with one that sonically resembles Velcro separating. Another is similar to ticking tones that resonate and subside at random intervals.

What’s that sound? Is it the eerie sound of an alien spaceship landing nearby? A white-noise soundtrack for people who have trouble falling asleep? Or is it the distinctive chorus of millions of ...

When birds or insects fly, they displace air with their wings – that is how it works. Maybe sometime at night you have disturbed an owl and heard the flap of its large wings. This sound is a frequency ...