For this week’s Please Explain, the Leonard Lopate Show finds out how we process all the sounds we hear every day—from the hum of the heater to the wail of sirens to music to speech—and how it shapes our brains and behavior.

Gretchen Reynolds, writer of the New York Times Phys Ed column and author of The First 20 Minutes, answers questions and debunks myths about exercise.

When you drop a letter in a mailbox, how exactly does it end up where it’s supposed to go? We’ll find out how the U.S. Postal Service works and why it’s struggling for survival. Nancy A. Pope, curator from the National Postal Museum and organizer of Systems at Work, and Richard John, professor at Columbia University School of Journalism and author of Spreading the News: The American Postal System from Franklin to Morse.

Corey S. Powell, Editor at Large of Discover magazine, talks about the biggest stories in science last year—including the new Mars rover; the discovery of the Higgs boson; the Human Microbiome Project; climate change, storms, and melting polar ice; private space flight; self-driving cars; the comeback of measles, mumps, and whooping cough; and more!

Today's Please Explain is all about helium and the helium shortage. We speak with Dr. Martin Stute, a noble gas geochemist at Barnard college and Lamont-Doherty Earth Observatory and with Dr. Joe Peterson a Bureau of Land Management Assistant Field Manager for Helium Resources in the BLM Amarillo, Texas Field Office.

For this week’s Please Explain we're picking up where last week's left off. We'll find out why stress can take a toll on our mental and physical health and find out how to reduce stress in our lives and cope with it better. We're joined again by Dr. Drew Ramsey, Assistant Clinical Professor of Psychiatry, Columbia University College of Physicians and Surgeons, and co-author of The Happiness Diet,  and  Dr. Rajita Sinha, director of the Yale Stress Center, and Professor of Psychiatry, Neurobiology and Child Study at Yale University School of Medicine.

This week’s Please Explain is all about stress—and why it can take a toll on our mental and physical health. We're joined by Dr. Drew Ramsey, Assistant Clinical Professor of Psychiatry, Columbia University College of Physicians and Surgeons, looks at how stress affects our health and ways to cope with stress and anxiety in everyday life. He’s co-author of The Happiness Diet. And Rajita Sinha, director of the Yale Stress Center, and Professor of Psychiatry, Neurobiology and Child Study at Yale University School of Medicine.

The Mayan calendar ends on December 21, 2012, prompting some to believe the world will end on that date. For this week’s Please Explain, we thought we’d find out about that calendar and the many others used through history by different cultures to account for the days and months that make up the year. Joining us are John Pratt and Ken Seidelmann, Research Professor at the University of Virginia’s Department of Astronomy.

Mold is a common household nuisance—it can appear on shower curtains and in damp basements and on aging foods in the refrigerator, but it’s a major concern in the aftermath of flooding caused by Sandy. Industrial hygienist and environmental health expert Monona Rossol and microbiologist Chin Yang, of Prestige EnviroMicrobiology, explain what mold is, where it comes from, how it grows, what it can do to your home and health, and how to get rid of it.

On this week’s Please Explain we’ll learn about the microbes, bacteria, and fungi in and around our households, hospitals and other buildings. Rob Dunn, biologist in the Department of Biology at North Carolina State University, project director of the Wild Life of Our Homes, and author of The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We Are Today, and  Jessica Green, Director of the Biology and the Built Environment (BioBE) Center at the University of Oregon, explain what these microbes are, where they come from, the ways their presence and absence may directly influence our health and well being, and new research into how to the design and operation of buildings to promote both human health and environmental sustainability. 

Christopher Hayes, Editor at Large of The Nation and author of Twilight of the Elites, talks about what’s been going on on the campaign trail with the presidential election just days away.

For Please Explain we’re looking at how experts predict the weather—and storms like Hurricane Sandy—and how improving technology is making the science more precise. Dr. Robert Gall, Development Manager of the Hurricane Forecast Improvement Program at the National Oceanic and Atmospheric Administration, and Dr. Adam Sobel, Professor in the Fu Foundation School of Engineering and Applied Science and the Lamont Doherty Earth Observatory at Columbia University.

Kate Ascher, author of The Heights: Anatomy of a Skyscraper, and Carol Willis, founder, director, and curator of the Skyscraper Museum, discuss the history and future of tall buildings—from Chicago’s 17-story Auditorium Building to Dubai’s 160-story Burj Khalifa. They’ll explain how they’re built, how they work, and how they’ve changed cities.

This week’s Please Explain looks at the outbreak of fungal meningitis from contaminated steroid shots. We’ll find out how epidemiologists trace outbreaks like this to their origins and what compounding pharmacies are and how they work. Dr. Emil Hiesiger, clinical associate professor of neurology, NYU  School of Medicine, and Dr. William Schaffner, Professor of Preventive Medicine and Chair of the Department of Preventive Medicine at Vanderbilt University and president of the National Foundation for Infectious Diseases, explain.

Jumping off buildings, running from a car engulfed in flames, getting into a brawl with a villain all some of the feats we see frequently in movies—and they’re performed by stuntmen (and women). Two experts join us to explain how stunts are performed in movies and on television: Hal Needham worked as a stuntman on more than 300 feature films and he was a pioneer in improving stunt technology and safety. He also directed the films Smokey and the Bandit, Cannonball Run, and Hooper, among others. He’s written about his career in Stuntman! My Car-Crashing, Plane-Jumping, Bone-Breaking, Death-Defying Hollywood Life. And Blaise Corrigan, a stuntman who has worked in New York for more than 20 years in such films as The Avengers, The Departed, The Bourne Legacy, and the television shows Boardwalk Empire, 30 Rock, and Law and Order.

From Apple's iCloud to Dropbox, cloud computing is becoming an increasingly important and useful part of digital life. This week's Please Explain is about the physical structures that make cloud computing possible, and their hidden impact on the environment. We're joined by James Glanz from The New York Times, who spent a year investigating the physical structures that make up and support cloud computing, and Dennis Symanski, Senior Project Manager at the Electric Power Research Institute.

Alena Grabowski, Assistant Research Professor at the University of Colorado Boulder, and research scientists at the Department of Veterans Affairs in Denver, and Mike McLoughlin, Research and Exploratory Development at The Johns Hopkins University Applied Physics Laboratory describe the latest prosthetic design and technologies and how they allow amputees to regain mobility.

For this week’s Please Explain, director Steve James talks about his new film “Head Games,” a revealing documentary about the concussions in American sports, along with former Ivy League Football Player and WWE Wrestler Christopher Nowinski, author of the book Head Games. It covers eye-opening evidence and cutting-edge science on head trauma from the nation’s leading medical experts and gives first-hand accounts from the athletes, coaches, and parents.

Thomas Bjorkman, professor of horticulture at Cornell’s New York State Agricultural Experiment Station in Geneva, NY, and Dr. Urvashi Rangan, Director, Consumer Safety and Sustainability Group at Consumer Reports, discuss what the organic label indicates about how food is grown, and what the various animal welfare labels indicate about how meat or eggs were bred and raised.

Monarch butterflies have started to make their long journey south to Mexico. On this week’s Please Explain, we’ll find out about the many different species of butterflies—from their coloring to their attraction to flowers to their cocoons. We’re joined by Bob Robbins, Curator of Lepidoptera, Smithsonian Institution National Museum of Natural History, and Dr. Cole Gilbert, Associate Professor of Entomology at Cornell University.