- Have you ever gone to a national park for a relaxing break in nature to only hear cars honking, people chit-chatting, (cars beeping) boombox's blaring?

Well, you're not alone.

People are noisy.

(bright upbeat music) According to a study from the National Park Service, 80% of the U.S. has human-made background noise.

We're going to speak with experts, Bernie Krause and Callie Leiphardt about how all types of manmade sound, like this, impacts creatures and what we can do about it.

And while human noise in outdoor places might be annoying to us, it can be really challenging for animals who rely on sound for food, communication, and even survival.

The term noise derives from the Latin word for nausea, which means any sound that interferes with other sounds.

However, the perception of noise and sound varies between individuals and even species.

(vehicle beeping) Do you hear that?

Sound itself is a series of vibrations that travel through the environment.

It can be a beautiful thing, something that inspires wonder and connection, like the sound of wind in the trees or a babbling stream.

(water gushing) While natural sounds, like waterfalls, can be loud, noise pollution specifically refers to unwanted sounds caused by human activities.

Noise pollution comes from things like cars, (traffic whooshing) planes, (plane engine rumbling) factories, (air whooshing) and even cities.

(indistinct chatter) Scientists have seen that animals in all sorts of places, from forests to the oceans, act differently because of this human noise.

I'm sure you're not surprised that the 20th century was the noisiest century in the history of the world, and now the 21st century is set to be even noisier.

As human population density increases, so too does the amount of noise we produce.

Even the most remote environments today are impacted by the sounds of our human world.

The study of acoustic ecology began in the late 1970s, but it just recently has been recognized as a useful means for determining the health of ecosystems.

(birds chirping) Legendary composer and soundscape ecologist, Bernie Krause, is a leading expert in the interplay between humans and animals as expressed through sound.

And I'm a huge fan girl.

We spoke with him about his work in California.

- I've been recording here since 1993, so it's like 31 years, if you could believe it.

When we first moved to Sonoma from San Francisco, my wife and I, and it finally became an objective to record every year in April, mid-April, to try to capture the dawn chorus to see how things would change over time.

The whole spectrum of bird sound is beginning to change.

Not only the species are changing, but the numbers of birds have dropped off radically.

We've actually had recordings in 2015 and last year, we've actually had recorded here when we got no bird sound at all, not a single chirp, 2015 and last year.

- Noise pollution affects birds in lots of different ways, like obstructing their ability to protect their territory, keeping in touch with each other and alerting others to dangers.

Bernie believes that every animal has something called an aural niche or its own particular voice and specific place in a habitat.

This is based on the relative frequency, amplitude, timber and duration of the sound the creature produces.

Altogether, the vocalizations of all the animals in a habitat zone produce a unique vocal footprint.

Which can be use to understand the ecological health of the area.

And it's important to protect this type of sound.

- I think we're hurting ourselves by not being quiet and listening and learning what the natural world has to teach us 'cause it's an incredible library of Alexandria that we're beginning to destroy.

- Human noise also impacts the creatures who call our vast oceans home.

Sound travels faster underwater than it does on land, making the underwater world a kind of information highway for its inhabitants.

But marine noise pollution produced from things like shipping and drilling creates a cacophony of sounds for marine animals, particularly whales.

This can change their behavior to avoid the noise, making them miss out on prime foraging or meeting opportunities and even cause hearing damage.

We spoke with Callie at Whale Safe, an AI-powered detection system, to hear how they are using technology to protect whales from shipping noise and vessel speeds.

- There's just nothing quite like seeing a blue whale for the first time.

Like, you have all these comparisons in your mind of, "Okay, "it's this big, or its heart is this big," and you kind of have all these, like, mental shortcuts of how you really think this animal is that large and nothing prepares you from seeing a blue whale.

- Whales are so charismatic.

They're the face of the work that we do, but they have such important impacts on the rest of the ecosystem.

They're really vital in keeping our oceans healthy.

And so by also doing the work that we're doing, it's having impacts all the way down in the food chain.

- There's a lot of co-benefits to some of this.

So when a ship slows down, it makes less underwater noise, which is better for all underwater creatures.

- From using technology to create quieter and safer spaces, to encouraging folks to get outside and listen, there's a lot of progress happening in the world of sound.

For one, if noise is reduced or simply turned off, it, more or less, resolves the issue.

The impact does not linger in the same way as other forms of pollution, like plastic or chemicals.

As we heard from Bernie and Callie, efforts are already underway.

- One of the things that I hope to do with that is to really inspire people to fall in love with whatever relationship they already have with the natural world by simply listening and paying attention.

We hear and learn from the natural environments by listening.

- I can't imagine doing anything that is more healing than just sitting here and being quiet.

- So get outside, take off those headphones, and definitely turn off your leaf blower.

Enjoy that really amazing aural niche of the environment around you, the sound of crickets, bird song and waves on the shore.

It's worth savoring and protecting.

Until next time, happy exploring.

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