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If you haven't heard the news that Mount Redoubt erupted yet, you must be deaf; but if you haven't actually heard the mountain explode, does that mean you're deaf too?

When Mount Saint Helens erupted in 1980, the boom was said to be heard as far away as Spokane and Eastern Washington.

Meanwhile people closer by didn't report hearing a thing.

"It's a very curious thing what people report about hearing volcanic explosions," said John Power, a geophysicist with the Alaska Volcano Observatory in Anchorage.

Power said that volcanic eruptions are such that they're often not audible from close range, say, the distance between Kenai and Redoubt, approximately 50 miles, but from much greater distances people will report hearing them.

Power said this is because human ears can't perceive the frequency of the sound waves generated in an eruption.

"It's like a dog whistle: there's no noise to us but our dogs can hear it," he said.

It's not to say that our dogs can necessarily hear volcanic eruptions, but their ears are capable of picking up on some frequencies, like those emitted from dog whistles, that we can't.

That doesn't explain however, how people hundreds of miles away do hear eruptions.

For this, Power explained that studies have suggested that sound waves from the explosions bounce off the stratosphere, changing their frequency and returning to earth as noise audible to humans.

Such has been the case even here.

"When Mount Spurr erupted in 1992, no one in Anchorage heard it, no one in Homer heard it and no one in Kenai heard it, but people climbing Denali did," he said.

Power recalled that a group of mountaineers in the park during the eruption called via satellite phone asking what was going on, and reported using their jackets to cover their ears for several hours while the explosions went on.

So if we can't hear the eruption, maybe we could at least feel it.

A quick glimpse at the earthquake data recorded by seismographs perched on the mountain and uploaded to the Internet in real time shows the mountain has the fidgetiness of a 4-year-old on a sugar high.

As it turns out, the instruments are very sensitive to Redoubt's rumblings.

Power said a person standing on the volcano couldn't detect most of the earthquake activity the seismographs pick up on.

Volcanic eruptions of Redoubt's types aren't typically associated with large earth shaking events either, according to Power.

"If we do get into a more energetic seismic sequence, it's possible we could feel them (earthquakes) in Kenai, but we wouldn't expect that to happen given what it's done in it's last eruption," Power said, referring to the series of eruptions of Redoubt between December of 1989 and April of 1990.

While we can't hear, feel, nor as of late see an eruption, we may of all things, occasionally be able to smell one.

"The bottom line is, volcanoes smell," Power said.

Volcanoes give off large volumes of gas, mostly in the form of odorless steam and carbon dioxide. On top of that they can emit some smellier gasses, like sulfur dioxide.

"That's principally the one you smell," Power said.

He noted that during the 2006 eruptions of Mount Augustine, peninsula residents could smell the rotten egg odor associated with the gas.

In the concentrations that typically make it across the inlet, Power said the gas doesn't pose a significant risk.

When emitted in large quantities, he said, the sulfur dioxide has resulted in acid rain fallout problems downwind of volcanoes. This has largely only been a problem for peaks that continually erupt in areas where trade winds tend to blow in only one direction, killing off vegetation and stunting agriculture downwind of the crater.

However, Power said he doesn't expect Redoubt to remain active long enough for this to become a problem.

Dante Petri can be reached at dante.petri@peninsulaclarion.com.